# Yamaha 2.5 4 stroke issues



## chucklesR (Sep 17, 2007)

My 2004 Yamaha 2.5 4 stroke is having what I think are carb issues 
(lo carb diet?)

After doing spring commisioning and testing last spring I loaned it to a friend last year as a kicker for his small sail boat and ultimately it got laid up without being used (read gas left in tank and carb for a year while laying in his basement).
I've drained the tank of the gummy gas, rinsed it with clean and refilled the tank. Drained all lines, drained the 'bowl' (really a tube) and cleaned it all out with carb cleaner and reinstalled the carb (and gasket). 
The motor will start and run with starter fluid sprayed into the air intake, and will occasionally pop with no starter fluid - but will not continue running once you stop spraying starter fluid. I've worn deep blisters on the index fingers of both hands pulling the starter and beginning to give up.

It seems like it's a fuel flow problem. Yes the fuel shut off was open (and turned to closed as well just to make sure I did not reinstall it back wards).
I also tried to start it with the vent to the tank both closed, and open (normal).

I took it back apart and blew into the fuel intake housing (where the gas tube goes into the throttle body) and no air flow was apparent, but I'm not sure if that is a good measurement. In either case the results were the same.

Right now the entire carb is sitting in a can of gum-out soaking. I really don't want to have to dissemble the entire carb as I don't have a rebuild kit and don't know the adjustments etc.. I'd have to make.

Anyone got any tips, hints, tricks or tales?
(besides not loaning equipment to friends


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## Freesail99 (Feb 13, 2006)

Take it to a repair shop, send your friend the bill. I have been there and you pull so many times that you end up crawling away rather then walking. Let go the stress, take it to be repaired.


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## theartfuldodger (Sep 4, 2006)

I have the same engine and went throught the same situation to find the vent in the fuel tank plugged, found this by providing a separate fuel source.


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## chucklesR (Sep 17, 2007)

Free, motor's worth 500, the shop costs 95 a hour, 3 hour minimum and as I said it's a friend - and he's standing right next to me as I work on it (it's sitting on a rack at his house now). Repair shop is not a option.

Art, I took the top off the tank just to check that, didn't help.


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## TSOJOURNER (Dec 16, 1999)

A couple of dollars spent on fuel lines (you didn't mention whether or not you replace them) would be a good idea. Before you cut and install the new fuel line, attach it to the carb still too long and filled with gas (be creative but careful) with the open end held up high. See if it will crank and run the gas out of the line. If it will, then the carb is ok.


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## chucklesR (Sep 17, 2007)

I did not replace the fuel lines because when I detached them from the carb the fuel ran just fine all over my index fingers newly blistered and open sores. Fuel appears to run just f%&ing fine up to the brass tube that goes into the throttle body.


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## Cruisingdad (Jul 21, 2006)

Ahhh... welcome to the wonderful world of 4 strokes. I had two strokes for a long time and hardly ever had issues. Is it just me, Chuckles, or do you feel like they suddenly decided one day to switch over to 4 strokes (and take away the 2's) without actually trying to start one at the factory?????

I have a Merc 6 that runs really well after every $300 tune up bill, until the 90 warranty is off and it is right back to CHug... spit... chug... die unless you have 1000 rpms on it.

Is your engine made by Tihatsu? I think it is.

At any rate, this will not help your current woes, but I have found the ONLY way to prolong (key word P-R-O-L-O-N-G) the time between shop visits is to run it dry everytime you go to put her up. Pull the fuel line and just let her go until she is dead (and I mean that in every possible sense). I also run a fuel cleaner in her. THis has helped considerably. If you do not run her dry each time, you will be faced with the same problem (exception is when you run her everyday. When we were Liveaboards, this was never a problem. Go figure??).

- CD


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## Iflyka200s (Oct 3, 2007)

Chuckles....

More bad news I'm afraid.......

I have a 2005 Yamaha 4hp 4 Stroke.... guy owed me money... Anyway mine sat for a year w/gas and it got so gummed up even though I took the carb off and cleaned it in the whoptie sonic aircraft parts cleaner at work....

I still had to rebuild it...it was just too gummed up even for the nuclear cleaner's I used on it.


Also sitting killed my fuel pump too...

Best of luck,

Tim


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## Joesaila (May 19, 2007)

I had the same problem w my 3.5 Tuhatsu. Thought I'd cleaned it out and it ran rough and only w the choke on. A friend suggested the needle valve was clogged so I added some carb cleaner to the gas. I put it in a barrel and got it running like a kitten in about 10 minutes.


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## Freesail99 (Feb 13, 2006)

> A friend suggested the needle valve was clogged so I added some carb cleaner to the gas. I put it in a barrel and got it running like a kitten in about 10 minutes.


I use to use carb clearner so much, a friend of mine, called it tune up in a can.


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## timebandit (Sep 18, 2002)

The only thing you may want to try is to check the float valve, sometimes the stick closed. 

Easy check is to open what ever type of bowl drain you have and then pump the bulb and see if fuel DOES get inside the carb and comes out the drain.

Remember that if a jet is cloged most cleaners will not remove it. You must use a wire or something to at least get a small hole through first. I use a strand from an old meter test lead.

You might also look in the little holes on the intake side of the carb to see if some little bugs have nested or died in there -- the biggest cause of ideling problems I have found.

It is kind of strange that a carb with less than an 1/2 ounce of fuel in it can go bad. There cannot be that much of solids in so little fuel as to clog anything.

And last but not least check the plug. My honda cannot be laid on side no mater what the book sez. Oil will run into the intake and foul the plug. 

good luck

Rick


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## timebandit (Sep 18, 2002)

Just cuz---I rarely need a gasket or rebuild kit to do carbs. Just be carefull when you take it apart. 

Write down all the adjustment as you take it apart.

Rick


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## chucklesR (Sep 17, 2007)

There is no 'bulb' to pump. I think, based on observation that it works on a vacuum, or just a plain old gravity feed. 
The vacuum part is why I'm insisting on a kit, with gaskets if I have to do a rebuild. 
It's in hold status letting my fingers heal and getting a 3 day soak at this point


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## timebandit (Sep 18, 2002)

OK OK
I am in fixit mode now.

I missed the size of the motor. I am guessing that it has a mounted fuel tank. You mentioned that you had turned the fuel lever on, and the tank vent open and there is a vacuum line---maybe leading to the fuel petcock??

The line going to the petcock opens the petcock only when the engine is producing vacuum.

Motorcycle using this type of petcock there is a position marked PRI "yup, for prime". This position manually opens the petcock to fill the carb so you dont have to crank the engine a lot.

I would imagine the running you did with the starter fluid should have filled the carb but not if there is a vacuum leak.

Just guessing cuz I couldn't find much online.

Rick 



chucklesR said:


> There is no 'bulb' to pump. I think, based on observation that it works on a vacuum, or just a plain old gravity feed.
> The vacuum part is why I'm insisting on a kit, with gaskets if I have to do a rebuild.
> It's in hold status letting my fingers heal and getting a 3 day soak at this point


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## chucklesR (Sep 17, 2007)

I found the problem with my 2004 Yahama 2.5 hp 4 stoke.

The problem is it was built in 2004. Ethanol gas was introduced in 2006.

The throttle body has a rubber pressed in seating, when turning the gas on and off the hole in the steel valve stem rubs the now gooey rubber in the pressed in fitting. 

Rebuild kit on the way.

Now the problem is when I put the engine in my trunk to take it home I put it on the wrong side - and have oil in the cylinders etc.. 

It never ends. Think I'll break out the oars for the rest of the summer.


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## sailingdog (Mar 19, 2006)

Chuckles—

Ain't technology wonderful....


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## chucklesR (Sep 17, 2007)

carbon fiber oars baby!


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## sailingdog (Mar 19, 2006)

I see you breaking one, like alex and his boom.


chucklesR said:


> carbon fiber oars baby!


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## PalmettoSailor (Mar 7, 2006)

I've got the exact same engine, though I think mine is an 05 or 06. Fortunately, the last thing I did with it last year was run it in bucket of freshwater mixed with antifreeze, then fogged it down and drained the remaining fuel.

Just last week I pulled the plug, checked the gapping, put in some fresh gas and it started on the 3rd pull. 

I do think this motor is not quite up to the task of moving my big behind in our Zodiac dingy. It seemed to load up like the plugs were fouling after a long run late last season. Taking the boat out of gear and revving it for a few seconds seemed to solve the problem. However we were a long way from our "big boat" and the pucker level was fairly high so, I bought a spare sparkplug in case we have trouble again this year.


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## timebandit (Sep 18, 2002)

A way to get the oil out of the cylinders----

Remove the prop and place the motor in a barrel.

Pull the plugs and rotate, put a rag over the plug hole.

Leave the fuel off.

Spray some starting fluid in the cylinder through the plug hole.

Install the plugs and run.

When the engine stops, and it will, pull the plugs and clean the oil from them with starting fluid.

Install the plugs and run again, and again untill the plugs are not bridged by oil.

Clean plugs one last time, spray the cylinder, install the plugs, turn on the gas and it should start right up.

You should only need to clean the plugs 3 to 4 times.

Please don't kill yourself pulling hard on the rope, if it is gonna start it will.

How to tell if a spark plug is good or not.

Open you hand, palm up, and place the plug in question on it. Extend you hand over the water. Now turn your hand over and count to ten. Turn your hand back over. 
If the plug is good it will still be in your hand!

Rick


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## 75R20 (Jun 20, 2008)

Add a spark plug to the job. It's amazing what bad gas will do to the plug, and its the last thing on the list.

Kary
#49080


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## TSOJOURNER (Dec 16, 1999)

Rick - I think that is how you find out if a small 4 stroke engine is good! As for me, I'll stay with 2 strokes as long as possible, pollution and all. I have a 5 year old 2HP Johnson which was put away without draining, oiling, or anything else 2-1/2 years ago. I put it on a plastic dingy, old gas and all, pulled it twice and roared away! My 10 year old Merc was put away last fall with fogging oil in the cylinders, drained tank and carb, but I cannot use it because the bottom peeled off my inflatable. The old plastic dink is too small to handle 7-1/2 HP.


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## JohnRPollard (Mar 26, 2007)

chucklesR said:


> I found the problem with my 2004 Yahama 2.5 hp 4 stoke.
> 
> The problem is it was built in 2004. Ethanol gas was introduced in 2006.
> 
> ...


ChucklesR,

How is it going with the Yamaha? Did you get it running again?

I was thinking about maybe picking one up for our dinghy:

THIS IS NOT A MISPRINT!!!!!!!!!!!!!!!!!!!

P.S. That's their phrasing for the link, not mine.


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## PalmettoSailor (Mar 7, 2006)

JohnRPollard said:


> ChucklesR,
> 
> How is it going with the Yamaha? Did you get it running again?
> 
> ...


Yeah well the MSRP might be over a grand, but I bet they never sold one for that.

I paid just over $700 for mine at a big Yamaha Outboard dealer in SC and thought I got a good deal. I'm only on my 2nd year with the motor but its met my expectations thus far.

Reading Chuckles travails with his just inspires me to make sure I store mine properly and keep it fed with fresh gas during the season.


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## chucklesR (Sep 17, 2007)

It's running just fine. My clean out missed a little pin hole in the brass thumbscrew looking piece that sticks down into the bowl. It has a slot in it that I took to be a screwdriver slot, center of the slot was a speck of crud that I surface cleaned, but didn't stick a needle in. 
I found it the fouth time through rebuilding it. 

On a positive note I can dis-sassemble a carb, clean it and reassemble it in under 30 minutes now 

I used that skill to get a 'gifted' 15hp Mariner 2 stroke running smooth in less than a hour, that'll be me zooming by in the noisy dinghy 'Lil Patience' when it's not hanging off the back of Patience Two; also sometimes home to 'Blow'in Patience my homemade sailing dinghy.

That's a okay deal, I got mine for 864 back in 2006.


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## TSOJOURNER (Dec 16, 1999)

*Carb crap wo's*

Hey there Chuckles, I have an Outboard repair bussiness and i see this everyday. it sounds to me that the jets in the carb are clogged. Even a small 2.5 needs to be able to breath. Year old gas and even 4 week old gas can cause the problem. The carb needs to be removed and serviced by a qualified technician like myself. I know that the best way to ensure your prompt return of this engine running properly is to get it to somone who knows whats up

Bill
Reliable Outboard Doc


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## TSOJOURNER (Dec 16, 1999)

*carb crap*

hey there chuckles, great job , that little thumb screw is the jet

way to go


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## negrini (Apr 2, 2008)

If you rebuilt the same way, there is little to adjust after mount. Mainly the air/gas mix needle. As a rule of thumb, close it all the way (gently) then turn it back counterclockwise 3/4 turn. Fire the engine and engage it in iddle, that should have enough torque to keep it running despite the prop load. If not unscrew it by 1/4 until you note a strong iddle.

4T use misery gas, so carb ducts passage are very tight, clogging very often. Take precautions stated here. To have a repair kit is also a good idea, and a bunch, a hudge amount of patience.


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## chucklesR (Sep 17, 2007)

ReliableOutboardDOC said:


> Hey there Chuckles, I have an Outboard repair bussiness and i see this everyday. it sounds to me that the jets in the carb are clogged. Even a small 2.5 needs to be able to breath. Year old gas and even 4 week old gas can cause the problem. The carb needs to be removed and serviced by a qualified technician like myself. I know that the best way to ensure your prompt return of this engine running properly is to get it to somone who knows whats up
> 
> Bill
> Reliable Outboard Doc


Bill, bottom line is I saved a couple hundred bucks by doing it myself - and learned in the process.


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## somers12 (Nov 8, 2007)

I had much the same problem with my 9.9 Nissan. It sat for a year, and I guess the gunk built up. Oh it ran just enough to make me confident enough to take it out to the lake. Damn thing left me stranded 3 times. Lucky there was enough wind to get me back to the dock. I felt like throwing it off the boat, but didn't.
The problem was resolved by buying a carb kit (diaphrams and gaskets) Which on after thought was probably unnecessary. I read that there are up to four different routes for the gas to flow depending on speed in a two stroke carburetor, so I ripped it apart and sprayed carb cleaner in every orifice, the thought being that with every hole, it has to come out somewhere. You've got to be careful, there are some pretty small holes there. I put it together and it runs like a top, and much faster and better than before. Try it.

Good luck ... Steve


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## TSOJOURNER (Dec 16, 1999)

Watch using to much starting fluid, it doesn't take much to wash your cylinder walls dry and cause wear and compression loss.


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## dvpamenter (Mar 3, 2000)

I had the same problem. Can't blame anyone but me. I expected it would be ok as were various previous 2 strokes. Used lots of carb cleaner. Ran with the choke out at first and slowly recovered usual performance. Lesson learned!


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