# tohatsu 3.5 won't run without choking



## TSOJOURNER (Dec 16, 1999)

Hi,

I have a 2002 3.5B2 3.5HP 2cycle that I purchased used last year. Worked great for 2 outings. Died the 3rd.

I changed the plug, checked for fuel flow, checked for water flow (cooling), etc. New gas, new oil. 50:1.

It starts great with the choke on. Whenever I move the throttle up or completely turn off the choke, it dies. Sounds to me like a fuel flow problem, but the line seems to be fine into the carb. Carb spray did nothing. My guess is that I need to get a rebuild kit for the carb, but before I start looking for one and go to the trouble, I wanted to ask for some friendly advice. 

Thanks!
Johnny


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## Faster (Sep 13, 2005)

Does it "wheeze" when it dies? We have had periodic problems over the years with one of our 5 hp nissans and always found some crud in one of the jets in the carb.

Don't think it's necessary to get a carb kit unless the engine is quite old. Pay attention as you disassemble it, don't lose any bits, and take out all the jets, inspect them and blow them out. As long as you haven't damaged the gaskets you should be able to reassemble it and be good to go for a while.

Very simple engines, most likely a carb problem.


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## Quickstep192 (Jan 6, 2001)

I had the same problem on my Honda. The jet orifices on these little motors are tiny and the tiniest bit of crud can clog them. I think it's likely to be the main jet which is generally accessed by removing the float bowl. You may find that the float bowl and/or the float valve are gunked up. You'll want to clean the entire carb, otherwise another piece of crud might find it's way right back in there. I've usually found disassembling the float bowl to be a dicey operation as the float valve can fall apart and its re-assembly might not be intuitive. Some companies sell a carb re-build kit which includes the jets and gaskets. Carb cleaner can be pretty hard on some of the gaskets and o-rings.


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## ysabelsdad (Mar 17, 2007)

I have a 5 horse Mercury that is doing something very similar. Can anyone recommend a decent book on maintaining and repairing small outboards. Most of the book I have seen seem to be oriented to larger engines.


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## Faster (Sep 13, 2005)

Here's a link from a google search... don't know anything about these books but maybe something here will look helpful....
Outboard Motor Manuals and books about Outboard Motors


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## Sapperwhite (Oct 21, 2006)

Seloc Marine has a book on about every engine out there.


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## ysabelsdad (Mar 17, 2007)

Bingo. Seloc is it. 

The outboard motor book store doesn't seem to carry anything on Mercury engines built passed the late 90s.


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## camaraderie (May 22, 2002)

I agree that the carb bowl and float are the likely culprits if you have good flow up to that point. It is pretty straightforward work to disassemble and clean and does not require a manual if you just go slowly and try not to have any pieces leftover when you put it back together!


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## eherlihy (Jan 2, 2007)

To clean the jets, I have always found that a blast of WD40 (Water Displacement formula 40) works wonders. If the crud is really stubborn, I have some wire-wrap (stiff, thin guage [AWG 30] wire) that I use to poke the crud through the holes in the jet. You can probably pick some of these up at your local electrical hobby store (Radio Shack, etc.).


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## chucklesR (Sep 17, 2007)

Sounds like fuel air mixture, but may not actually be the carb/choke.

How about the gas cap - most have vents that need to be opened when running, closed when carrying? Do / did you remember to open yours?

Look for simple solutions first, then start poking around with tools.

How much time elapsed between running it the second and third time? Is the fuel bad? If the carb isn't varnished (brown coating on the metal) it might be just a blow out the jet's issue, if it's varnished soak it as a unit and try it before taking it apart. 

Did you refill with E85 and melt the innards?

Is the choke set and operating properly (not sticking, popping once hot etc..). Again, going with the simple solution first make sure it's operating correctly since the engine shuts down when you close it, or speed up the throttle. - it might not be fuel, it might be air 

It might be fuel, but look for the easy, single answer to a single problem solution first.


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## TSOJOURNER (Dec 16, 1999)

Hi, 
Thanks for the responses!
No wheezing. After I throttle up, it sounds like it is starving for gas.
It was only a few weeks between runnings, so gas was good. Vent was open
I did visually verify operation of the choke/throttle yesterday, so that's not it. New plug/oil/fuel yesterday -- same problem.

The outside of the carb has a small amount of varnish(likely from old spillage), but not much. The (new) plug was very slightly darkened after a few minutes of running, but not fouled or burned, so that looks OK.

Disassembling the carb is likely in my future. I'll let you know what I find! If I do destroy the gaskets, any recommendation on where to order replacements?


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## camaraderie (May 22, 2002)

For parts: 
Tohatsu Outboards: Authorized North American Distributor for Tohatsu Outboards, Parts, & Accessories.


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## TohatsuGuru (Oct 3, 2007)

You have a 99.99% chance of the carburetor orifices being clogged up. You will have to remove the carburetor and disassemble it before dipping the body and metal parts in carburetor cleaner. Under no circumstances can you place the plastic, rubber or fiber parts in cleaner as that will either dissolve them or cause them to swell. Any Nissan, Tohatsu or Mercury dealer has parts for this model engine.


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## hphoen (Apr 3, 2003)

My last two outboards have been Nissan and Tohatsu, both made by Tohatsu. They have been absolutely great in starting. The only time I had any problems was when I used "old" fuel--three months old. Went to the fresh stuff, and it fired right up. Make sure your gas is new!


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## sailaway21 (Sep 4, 2006)

You say the fuel flow is good. I'd change the fuel filter anyway. Don't ask me how I know this.


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## TSOJOURNER (Dec 16, 1999)

*fixed!*

Well, as suspected it was a piece of gunk clogging the jet inside of the bowl. All cleaned and runs great.

The wirewrap wire was a tool that worked great too.

Thanks for the advice!


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## camaraderie (May 22, 2002)

Thanks for the follow up report. It is always good to know if diagnosis and suggested fixes pan out. Glad yer back up and running!


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## TSOJOURNER (Dec 16, 1999)

Does it have a fuel pump? My 15 hp Nissan was doing that and it turned out to be the fuel pump, Which is a rubber sheet with one side being connected to the crankcase (making it flutter as the engine runs) and the other side having a set of one way valves. There was a leak around the sheet and it wasn't sealed to the crankcase and didn't flutter. Took it apart put some gasket sealer around the edge, put it back together, and boom it worked.


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## Alden68 (Mar 21, 2007)

Jshep and all:

As Chuckles pointed out there is a real problem with E85 and your dink motor.

My Merc is 2 years old and wouldn't run without the choke. Had to have the carb rebuilt and the mech said "let me guess....you fill up a 5 gall tank in your dink and it sits there all season." Yup. Well the ethanol causes the gas to separate as it just sits around and this was contaminating my carb. He suggested only using .5 to a gallon at a time. More trips to the gas station but fewer trips to see him!


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## NautiG (Apr 23, 2007)

Running the engine dry (ie disconnecting the fuel line, or shutting off the fuel valve) would also probably help in preventing the carb from getting clogged. I have a couple two cycle engines, and I try to shut them off by cutting off the fuel supply, instead of turning the on/off switch. Especially if I know the engine is going to sit awhile without use.

Scott
Gemini Catamaran Split Decision
Captain's Blog


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## TSOJOURNER (Dec 16, 1999)

I had the same problem with my Tohatsu 8Hp. It was the ethanol clogging my jets. Had to clean the carb and used additive after that. If you can find any 100 octane racing fuel (ethanol free) run a tank of that, it will clean out the carb. Use additive after that, if your gas is going to sit for a week or more. Personally, I think your better of using it all the time.

Bob C s/v Valkyrie, Irwin Citation 35.5


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## TohatsuGuru (Oct 3, 2007)

Service manuals for each brand are available from their respective dealers. The generic manuals often have errors and fail to address some aspects of repair on individual models. Clean the carb by taking it apart and soaking the appropriate pieces in carburetor cleaner. Nothing you can spray into it will dissolve the plugged jets and ports. Spray cleaners should be looked at as a preventive maintenance item rather than as a repair tool.


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## Omatako (Sep 14, 2003)

*I haven't read the whole post yet . . . .*

. . . . so I hope I'm not wasting your time.



ysabelsdad said:


> I have a 5 horse Mercury that is doing something very similar. Can anyone recommend a decent book on maintaining and repairing small outboards. Most of the book I have seen seem to be oriented to larger engines.


Try this site. It costs 15 odd dollars but I down-loaded the Mercury 1989 to 2000 manual and I'm really pleased with the result. This covers all models of Mercury from 2.2 hp to the big daddies.

Technical Download PDF / Text Suzuki GSXR 1000 Service Repair mercury

Andre


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## Omatako (Sep 14, 2003)

By now you have probably found the problem but here's a quick fix that often works for this type of problem.

Take off what you need to get to the inlet of the carb - run the engine up to a reasonably high RPM and then while holding the throttle open, block the airway (I try to use the palm of my hand).

The vacuum has to be drawn from somewhere and often it will draw bits of rubbish through the main jet and clear it. If it doesn't work, you haven't wasted too much time.

Andre


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## bb32 (Jun 14, 2006)

Just found this thread the other day while trying to fix my friend's Tohatsu 3.5 2 stroke. What the problem turned out to be was the petcock was blocking the fuel flow to a few drops a minute when full open. Unable to disassemble it but there seems to a rubber washer or check valve that only allows fuel to flow in one direction. It was either gummed up or swollen from the ethanol and would allow just enough fuel to idle but not enough to get to half throttle.
Sprayed carb cleaner let it soak and blew it out with compressed air.
Motor now running better than it has in years


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## flatracker (Aug 16, 2009)

*To avoid this problem*

To avoid this problem in the future, if it is jet stopped up from crud, which I think you will find to be the cause. When you finish for the day with the engine, shut off the fuel and run the carb. dry. Modern?? gasoline is horrible, and while sta bil will keep it usable for some time, when it evaporates, still leaves junk behind, which stops up jets. Running it dry will eliminate this problem.


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## philsboat (Oct 16, 2006)

I found a tip from a motorcycle forum for dirty carbs.Buy a can of flammable carb cleaner.Drain out all of the gas from the motor.Put enough carb cleaner in the tank to run the engine.Start the engine and run until the carb is full of cleaner.(make sure the proper amount of oil is mixed with it if it's 2 cycle)Shut the engine off and let it sit for a day.Take it for a run with fresh gas and see what happens.
This saved the Triumph motorcycle owner $450 ($150)per carb.Costs $5 to $10 bucks.Make sure the cleaner is ok with plastic parts,it should be written on the label.

Phil


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## TohatsuGuru (Oct 3, 2007)

That's not a great idea. Most carburetor cleaners will dissolve the rubber and plastic components of the average carburetor. The only safe method is to remove the carb off of the engine, take it apart, dip the metal parts in carb cleaner for at least three hours, wash off, blow dry and re-assemble.


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## roline (Apr 7, 2000)

I have a Johnson 3.5 internal tank on my 525, always shut the gas off, run the gas out of the carb, raise it and tilt it , place the sunbrella cover over the engine. I've done that for over 12 yrs. It starts on the third pull and runs strong. Try to find 100% gas, we just have a few stations that still sell it in our area. Only problem to date, watch out for the mub dobbers, they will make a nest in the strangest places like air cleaners or water exit tubes...


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## eherlihy (Jan 2, 2007)

Mentioned elsewhere in this thread (and Sailnet) is the fact that alcohol (the 15% of E85) eats rubber. (try this experiment at home - pour some isopropyl alcohol into a dish, put a peice of black rubber - say a peice of an old windshield washer into the dish, let stand for 12 hours. Do you see any change in the rubber?) 

The problem with this motor is most likeley that some rubber in the fuel supply (gasket, fuel or vacuum line) has partially dissolved and is either gumming up the carb, or causing a vacuum leak.

The FIX is to identify the damaged rubber component(s) and REPLACE it(them) - preferably with a like component that is not affected by alcohol. Rub a Q-Tip over suspect parts. If the cotton turns black, or gets little gooey black blobs on it, then you've found a problem. Then clean the rest of the fuel system (needle valve seats, venturi, jets, etc.).

The best preventitive measure is to run the motor dry, but then you may have to worry about corrosion. If this is a concern, then spray a can of motor fog into the carb before storing it.


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## mattosdf (Jan 8, 2009)

*3.5hp*

is this siimilar to evinrude 3.3?


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## Diamondjet (Apr 8, 2010)

Resurrected thread. Found that new carb for 4hp Tohatsu is $108. Rebuild about 40-50. I haven't heard anybody point out that the Tohatsu/Nissan is almost impossible to throughly clean. The choke butterfly, carb intake butterfly linkage and choke linkage are plastic and I have not been able to remove them from the carb body prior to soaking the carb in cleaner (and I'm not sure it won't melt in carb cleaner). Factory manual is weakly written for 'how to' but does give assembly order and specifications. The idle jet is under a brass plug and can be difficult to remove. The main jet often corrodes in its' threads and the brass screwdriver slot can give way before the jet releases. If. any reader has solutions to the above I'd sure like to hear them. I hate to replace the carb every few years and fortunately I've just found a source for alcohol free gasoline a couple of blocks from my house which may extend the time between cleanings.


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## pvanv1 (Nov 16, 2007)

*Difference btw M3.5B and MFS4*

Diamond,

The OP was talking about the old 3.5B, with slide type throttle. Yours is an entirely different animal. We clean them all the time (few a week) in my shop. Must be done in carb dip. Period. Better yet, if your carb was abused by letting gas sit in it too long... for your MFS4... would be to install a new carb for the MFS6B (identical powerheads), and clean up the old carb as a spare. 50% more hp, too. We do it all the time.


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## Diamondjet (Apr 8, 2010)

pvan1.....do you remove the plastic parts prior to carb dip? I found the manual did not refer to this and the plastic parts don't just 'pop' off. The choke butterfly appears to be press fit in a slot on the intake side and the levers for both throttle and choke are apparently press fit on pins. Is that the way it is??


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## captflood (Jan 1, 2011)

GREETINGS EARTHLINGS sounds like your treating the symtoms and not the curse it must need an extra fuel fillter if there is space for it GO SAFE


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## Diamondjet (Apr 8, 2010)

I'll replace fuel filter and try it. Idling is poor on both my '05 Nissan 4hp and 2001 Tohatsu 5hp. Nissan just got the carb and new fuel filter. Tohatsu in my shop now. BTW...............How important is ethanol free gasoline?


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## captflood (Jan 1, 2011)

GREETINGS EARTHLINGS Always let your fuel sit for a while before you put it in the tank too let the water seperate then fillter then place in fuel tank GO SAFE


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## skygazer (Sep 3, 2011)

Can't buy ethanol free gas around here that I know of. Captflood, what do you do with the water at the bottom of the gas can if it separates out? Isn't it part gas part water?

Burn pile??


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## dabnis (Jul 29, 2007)

skygazer said:


> Can't buy ethanol free gas around here that I know of. Captflood, what do you do with the water at the bottom of the gas can if it separates out? Isn't it part gas part water?
> 
> Burn pile??


Berryman's B-12 fuel additive "absorbes" the water and it goes out the exhaust. No affiliation, it just works for me for many years, no fuel related problems during that time. Suggest reading the instructions, it can melt paint and some plastics, good stuff!!, they will probably ban it in California soon, it works that well.

Dabnis


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## captflood (Jan 1, 2011)

GREETINGS EARTHLINGS. Any leftover deposits or fluids that are unwanted and are in need of dissposal I normaly feed to the weeds in my drive (Dandylions Mainly), Or go into a bottle used to wash-down engine bits, GO SAFE


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## Diamondjet (Apr 8, 2010)

Looking for more detail than the factory manual offers in terms of carburetor disasembly if anyone cares to share their experiences. How can you throughly clean the carb body in normal carburetor cleaner dip if you cannot remove the plastic parts first? Do any readers have experience with having removed the idle jet under the sealed brass plug? Don't say "manual" please. The manual setting in front of me is full of specifications (which are needed) but short on techniques (as are most 'factory' manuals). 

I did a search on ethanol free gasoline and most posters indicate that anything greater than 10% ethanol content plays havoc with our small engines and there are some who claim that even 10% content is damaging. Hard to quantify this but many local operators of small outboards are aware of the issues of 'old' gasoline. Most don't use ethanol-free gas which I have recently found to be available nearby.


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## pvanv1 (Nov 16, 2007)

Diamondjet said:


> pvan1.....do you remove the plastic parts prior to carb dip? I found the manual did not refer to this and the plastic parts don't just 'pop' off. The choke butterfly appears to be press fit in a slot on the intake side and the levers for both throttle and choke are apparently press fit on pins. Is that the way it is??


The plastic actuators stay on. The procedure is a full disassembly, including jets and emulsion tube nozzle. All non-rubber/non-gasket stuff goes into the dip basket for 4 hours at room temp. Then an aggressive spray out with generic carb spray. Then careful reassembly, verifying float settings.


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## pvanv1 (Nov 16, 2007)

dabnis said:


> Berryman's B-12 fuel additive "absorbes" the water and it goes out the exhaust. No affiliation, it just works for me for many years, no fuel related problems during that time. Suggest reading the instructions, it can melt paint and some plastics, good stuff!!, they will probably ban it in California soon, it works that well.
> 
> Dabnis


Not chemically possible, unless it is an alcohol- or soap-type emulsifier. VooDoo doesn't help much, either. Stabilizer slows the fuel rotting, but not much else.


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## pvanv1 (Nov 16, 2007)

captflood said:


> GREETINGS EARTHLINGS sounds like your treating the symtoms and not the curse it must need an extra fuel fillter if there is space for it GO SAFE


Negative. The Tohatsu filter is 10 microns. If contaminated or clogged, replace it. If you have a remote tank, a water-separator filter is a good idea. In any event, a baja-type filter funnel is never a bad idea. Start with clean, fresh fuel, and keep it that way.


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## pvanv1 (Nov 16, 2007)

Diamondjet said:


> I'll replace fuel filter and try it. Idling is poor on both my '05 Nissan 4hp and 2001 Tohatsu 5hp. Nissan just got the carb and new fuel filter. Tohatsu in my shop now. BTW...............How important is ethanol free gasoline?


If you can avoid the E gas, cool. If not, be religious in using only clean, fresh fuel. Always run the carb dry at the end of each day, and enjoy many years of clean carb.


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## pvanv1 (Nov 16, 2007)

Diamondjet said:


> Looking for more detail than the factory manual offers in terms of carburetor disasembly if anyone cares to share their experiences. How can you throughly clean the carb body in normal carburetor cleaner dip if you cannot remove the plastic parts first? Do any readers have experience with having removed the idle jet under the sealed brass plug? Don't say "manual" please. The manual setting in front of me is full of specifications (which are needed) but short on techniques (as are most 'factory' manuals).
> 
> I did a search on ethanol free gasoline and most posters indicate that anything greater than 10% ethanol content plays havoc with our small engines and there are some who claim that even 10% content is damaging. Hard to quantify this but many local operators of small outboards are aware of the issues of 'old' gasoline. Most don't use ethanol-free gas which I have recently found to be available nearby.


The factory manuals are primarily written for mechanics, so the authors expect you to have some carb repair skills already. It is possible, but not recommended, to remove the EPA-mandated plug to access the pilot screw. Very difficult to re-set that correctly in the field. I have done it in the controlled conditions of the shop, with the aid of precise shop instruments and a very good ear. Don't bother. After a bath in carb dip, and a blow-out with generic carb spray, you should be fine.

No outboards of any make are designed for more than 10% ethanol, nor more than 5% methanol. In addition to "cleaning" out the delivery network before you buy it (the cleaned stuff becomes part of the fuel, yuck), E gas dries a lot of rubbers and absorbs water from the air. Eventually that water can separate, causing corrosion in the lower areas of anything metal in the fuel system.


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## Diamondjet (Apr 8, 2010)

Thanks........that's some good information! I've got an extra carb body now to experiment with and so time to work with. I'll post results.


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## smallboatlover (May 11, 2011)

i had the same problem with a motor i barrowed from a freind it wouldn't run unless choke was on. so i just ran it like that and it ran perfect.


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## pvanv1 (Nov 16, 2007)

smallboatlover said:


> i had the same problem with a motor i barrowed from a freind it wouldn't run unless choke was on. so i just ran it like that and it ran perfect.


And you could run a motor with a rod knock, as long as you wear ear muffs. But that is not how it was intended to operate.


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## dabnis (Jul 29, 2007)

pvanv1 said:


> Not chemically possible, unless it is an alcohol- or soap-type emulsifier. VooDoo doesn't help much, either. Stabilizer slows the fuel rotting, but not much else.


Paul,

I can only speak from my own experience.I put some gas in a coffee can, added some B-12 fuel additive, and the water was no longer visible, apparently blending with the gas to be burned away? As mentioned earlier I have used it for many years in many different motors, both 2 & 4 stroke with no fuel related problems. Of course, using it is voluntary, and your mileage may vary 

Dabnis


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## LakeSuperiorGeezer (Oct 8, 2010)

In Wisconsin the premium gasoline (91 octane) does not have any alcohol.


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## pvanv1 (Nov 16, 2007)

dabnis said:


> Paul,
> 
> I can only speak from my own experience.I put some gas in a coffee can, added some B-12 fuel additive, and the water was no longer visible, apparently blending with the gas to be burned away? As mentioned earlier I have used it for many years in many different motors, both 2 & 4 stroke with no fuel related problems. Of course, using it is voluntary, and your mileage may vary
> 
> Dabnis


Quite possible. We get the same effect from the K-100 additives, which we sell and use. The K-100 is an emulsifier of some kind, and not a bad thing. However, with E gas, once it has separated, you can't "put the genie back in the bottle". The alcohol is used as an octane booster, amongst other things, and the "restored" fuel will still be below octane specifications, causing other problems as well. It's a cheat that may get you by. Still preferable to run fresh, clean gas.


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## dabnis (Jul 29, 2007)

pvanv1 said:


> Quite possible. We get the same effect from the K-100 additives, which we sell and use. The K-100 is an emulsifier of some kind, and not a bad thing. However, with E gas, once it has separated, you can't "put the genie back in the bottle". The alcohol is used as an octane booster, amongst other things, and the "restored" fuel will still be below octane specifications, causing other problems as well. It's a cheat that may get you by. Still preferable to run fresh, clean gas.


What are your thoughts on something like this:

Cabela's: Nissan Fuel/Water Separator and Replacement Filter

Dabnis


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## pvanv1 (Nov 16, 2007)

dabnis said:


> What are your thoughts on something like this:
> 
> Cabela's: Nissan Fuel/Water Separator and Replacement Filter
> 
> Dabnis


I sell them and recommend them.


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## dabnis (Jul 29, 2007)

pvanv1 said:


> I sell them and recommend them.


OK, so noted. Thanks for the reply.

Dabnis


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## LittleDevil (Sep 15, 2010)

*Re: Difference btw M3.5B and MFS4*



pvanv1 said:


> Diamond,
> 
> The OP was talking about the old 3.5B, with slide type throttle. Yours is an entirely different animal. We clean them all the time (few a week) in my shop. Must be done in carb dip. Period. Better yet, if your carb was abused by letting gas sit in it too long... for your MFS4... would be to install a new carb for the MFS6B (identical powerheads), and clean up the old carb as a spare. 50% more hp, too. We do it all the time.


Sorry to dig up an old thread, but I have a 2008 Mercury 3.5HP 4 stroke. Will this carb (MFS4) fit that as well? Thanks!


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## pvanv1 (Nov 16, 2007)

Nope. The 3.5 4-st is the "big brother" of the 2.5, and is already upgraded.


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## LittleDevil (Sep 15, 2010)

Okay thanks. Well I changed the plug, cleaned out the tank, cleaned out the carb, cleaned out the petcock, cleaned out the lines, cleaned the air screen, blew out and cleaned the air lines that run to the bottom of the engine compartment and put fresh premium fuel in. I wasn't sure how many turns to put on the one screw in the back of the carb, so I screwed it all the way in until the spring bottomed out, and then turned it out 2-3/4 turns, which from memory, should be about right. I put the tank back on and now I can't get to the adjustment screw. Seems like a dumb design but oh well.

I started it right up and it actually idled great with the choke off. Problem is that it still will not run once you throttle up, unless you choke it about half way. I opened the fuel cap to see if that helped. Same deal. This is what it was doing before. Has anyone figured this out? I was pretty meticulous about cleaning out all parts of the carb and jets, although I could not figure out how to get the float off without breaking the clip that holds it on. I did my best to spray that out and confirmed cleaner was squirting out another part of the carb.

I got this motor as a package with a sailboat, and it has never worked right. This is the second time I've tried cleaning it. Oh and I recently read about an inline filter. That is one thing I did not find. Can anyone tell where that is and how to take it out, clean or replace it?

Any other advice here?


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## dabnis (Jul 29, 2007)

I had a Honda 2HP. It had a very small fine mesh filter inside the fuel line just at the tank outlet. You can't see it from the outside. Yours may be similar?

Paul T


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## LittleDevil (Sep 15, 2010)

I'm guessing you just pluck it out? If so, how do you get it back in? I'll dump the fuel and take a look. Thanks.


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## Sea Dawg (Jun 26, 2012)

Sapperwhite said:


> Seloc Marine has a book on about every engine out there.


Agreed, Seloc has a way with words to help you understand your motor. I would recommend it over any others.

If choking it keeps it running it does sound starved for fuel. Float valve can stick or stuff can block flow even if the float and valve operate correctly. I had a head gasket leaking water into the combustion chamber on a 2 HP older motor and with choke on it would at least run. The evidence was in removing the spark plug and shining light on the piston to observe tiny droplets on the piston. Very little water, but gasoline will generally not leave this evidence so I replaced head gasket. The gasket gave me even better indication where the leak was.

Lastly, if the float or valve were not filling the carb bowl with gas due to sticking would expect a shot of starting fluid while it falters would bring up the rpm as the fuel shortage would be remedied and the intake path wouldn't be blocked. Hope this helps and let us know what you find.


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## pvanv1 (Nov 16, 2007)

You did not adequately clean the carb. Carb spray itself it not aggressive enough to dissolve the organic varnishing in the low-speed passages. You must completely disassemble it (including jets, emulsion tube nozzle, and of course the needle and float). Then submerge in real carb dip for 4 hours at room temperature. THEN blow it out with generic carb spray, and reassemble, paying close attention to the float height.

You did not need to adjust the pilot mixture screw. But, since you did... It should not bottom out the spring; it should Gently seat in a delicate brass jet in the carb. The correct initial setting is about 1-3/4 turn out, and once the motor is running OK and fully warmed, you would then adjust it as on any other carb on any other motor. If you are not familiar with that procedure, or don't have a very good ear and a razor-accurate shop tach, get assistance from someone who does. Yes, you must pull the fuel tank bolts to make that adjustment... But since you are "never" supposed to change it, that's not a big deal.

There is in fact an inline filter screen between the fuel **** and the tank, which should be inspected.

HTH


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## pvanv1 (Nov 16, 2007)

Sea Dawg said:


> Agreed, Seloc has a way with words to help you understand your motor. I would recommend it over any others.


The Factory service manual (either the Tohatsu or Mercury) is head-and-shoulders above the Seloc, generic, one-manual-fits-all, publication. For one thing, it explains how to disassemble the carb, which so far has not been done.


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## tweitz (Apr 5, 2007)

I have a Tohatsu 3.5 as well. I have an intermittent problem driving me nuts. Most of the time it starts reasonably easily. Once started it runs fine But once in a while it is dead as a door nail. Yes the fuel **** is open, the fuel tank vent is open, the starter kill switch is in place the choke is pulled. I am inclined to think it is electrical, but have been unsuccessful in finding the problem. Any suggestions?


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## TohatsuGuru (Oct 3, 2007)

You open the manual and start running the tests on the ignition system or you can randomly replace parts hoping that the shotgun approach will yield a positive result.


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