# Carb(fuel flow?) issues with Honda 7.5 outboard



## blobaugh (May 26, 2011)

I have a Honda 7.5hp outboard on my sailboat that is acting up. I can get it to fire with the throttle and choke open, but have to push the throttle in halfway and leave the throttle open for it to stay running. It will not idle at all anymore. I am thinking there is a restriction in fuel flow somewhere, probably in the carb. I have heard that Honda's can be weird to work on, but I want to give it a shot myself before shelling out the big bucks to get it fixed. Are there any suggestions on where or start and/or resources (websites, books, parts dealers, etc) you can point me at to address the problem?


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## whorne (Jul 4, 2010)

Your problem sounds exactly like what I experienced with the exact same engine. I emptied my gas tank and let it dry out inside, filled it with fresh gasoline and it now runs like a top.


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## erps (Aug 2, 2006)

If it were me, I'd start by pulling the carb off, dropping the bowl then the float and needle valve then I'd spray some carb cleaner and blow the heck out of it with compressed air and put it back together. A good many times, that will clear a piece of crap that got stuck in the low speed circuit. If it doesn't work, then it's more work and more troubleshooting, but you have to start somewhere and may as well try the easy stuff first.

edit: What Whorne said even sounds easier.


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## blobaugh (May 26, 2011)

I always disconnect the tank after use. The gasoline in it is fresh. I have refreshed the gas twice. Tried some liquid carb cleaner in that also. I disconnected the fuel line while the motor was running and let it go dry. That did not work.

@erps - That is what I am thinking I may need to do, however I have never worked on an outboard before so I am looking for some guidance on how to do that. Do you know of any resources, books, sites, etc that provide solid guidance on the matter?


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## dabnis (Jul 29, 2007)

whorne said:


> Your problem sounds exactly like what I experienced with the exact same engine. I emptied my gas tank and let it dry out inside, filled it with fresh gasoline and it now runs like a top.


 Also suggest you drain the carb, leave the drain plug open and open the gas valve and let some fuel flow through. If it has an external tank, squeeze the ball.
If that doesn't work try ERPS suggestion, been there, done that. My experience working with Honda was little different than Evinrude/Johnson. Just lay out the pieces in sequence, "up" side up and reverse to re-install. A big clean towel makes a good working surface.

Paul T


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## blobaugh (May 26, 2011)

Know of any good diagrams?


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## erps (Aug 2, 2006)

> That is what I am thinking I may need to do, however I have never worked on an outboard before so I am looking for some guidance on how to do that. Do you know of any resources, books, sites, etc that provide solid guidance on the matter?


I had a Honda 7.5 back in the late 80's, as did my father. We both had the carbs apart while troubleshooting another problem that is fairly common with those motors. The exhaust manifold starts leaking exhaust gases into the engine cover which leads to low power and stalling out at higher RPM's. It's been so long, I don't recollect how daunting the task was, but we both did it while travelling on vacation with the limited tools that were in our boats. I'll see if I can find an exploded view of the carb somewhere and post a link.


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## blobaugh (May 26, 2011)

Thanks. I will take a look at that manual and see what I can figure out


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## erps (Aug 2, 2006)

another thread on the topic:

http://www.sailnet.com/forums/gear-maintenance/4233-1981-honda-9-9-4-stroke-o-b-idle-problem.html


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## erps (Aug 2, 2006)

> Thanks. I will take a look at that manual and see what I can figure out


Sorry, I posted the link before I looked at the manual. It was an owner's manual, so i deleted the link and my post. I wasn't quick enough though. Sorry.


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## Minnewaska (Feb 21, 2010)

If you want to try some witchcraft first, get a can of Valvetech Carb Free and spray it down the carburetor while the engine is running a higher rpm in idle. Says to use the whole can, not just a few squirts. I've never used more than half a can. You let it sit for 15 mins, then run her up to burn out residue. I have found it to work, but that presumes the problem is just varnish from old gas and not a real mechanical issue.

Changing to a new properly gapped spark plug can do wonders too.

Then, search online for a maintenance, repair or service manual for your outboard. Looks up how to adjust the idle, etc. A few twists of a screw could be all she needs.

These may be worth trying before spreading all the part of a small carb out on a workbench. However, ethanol in gasoline is notorious for eating some carburetor parts.


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## erps (Aug 2, 2006)

Pre-1997 BF75 SA Honda Outboard Parts


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## whorne (Jul 4, 2010)

I have a repair manual if you can't find one I will share


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## dabnis (Jul 29, 2007)

Minnewaska said:


> If you want to try some witchcraft first, get a can of Valvetech Carb Free and spray it down the carburetor while the engine is running a higher rpm in idle. Says to use the whole can, not just a few squirts. I've never used more than half a can. You let it sit for 15 mins, then run her up to burn out residue. I have found it to work, but that presumes the problem is just varnish from old gas and not a real mechanical issue.
> 
> Changing to a new properly gapped spark plug can do wonders too.
> 
> ...


Another approach is to make up a 50% mix of fuel and carb cleaner and run it through the engine for a while. Let it set for a day or so and then drain the carb and start over. There is probably a low speed mixture screw which you could try adjusting. On just about all the carbs I have worked on a good starting point is 1-1/2 turns open after it is closed all the way. Don't turn it too hard when closing it.

Paul T


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## whorne (Jul 4, 2010)

Has anyone suggested a fuel pump kit?


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## Capt Len (Oct 9, 2011)

Not familiar with the honda 7.5 but with carbs with high and low jets can catch a bit of dust, varnish or stuff in the orfice. Idle jet If you screw open the needle valve first to dislodge the bit ,then in to close ,then back off for idle speed it may clear. Then the high speed. Usually running too rich and needs an adjust. Probably fouled the plug by now so having a spare is good. 4 strokes are sensitive to base oil level and cooling water if you don't carry it right.


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