96 Yamaha OB possible fuel issue

[alchik]

Hi,

When I took my boat out the first time this year (Yep, very late in the season since I work too much) I noticed an issue with the motor cutting off. I'll put in, go wake speed with no real issues for about 400 yards or so till I'm out of the wake zone then I'll open it up and go approximately 100 yards or so and it will just die as if the fuel flow was cut off. I had a similar issue a couple of years ago when I had a primer bulb go bad. Anyway, I try to crank it to no avail until I pump the primer bulb and then it fires up but will only go about 50 yards or so then stop again (I'm just going wake speed at this point.). I end up having to pump the bulb every few minutes to limp back to dock. So, I'm thinking a bulb issue again. I end up cleaning out the fuel filter, replacing the fuel/water separator, fuel lines and the bulb. I go out again and the same thing happens. Exactly as it did before. So I limp back and go home. This time I've got some carb cleaner spray that you spray in the throats while running. So I do that till the can is empty, let it soak overnight. I go out again the next day, same friggin thing. Wake speed ok for 400 or so yards, open it up for about 100 yards then it dies. After that I have to keep pumping the bulb to limp back. I suspect I may have to clean and rebuild the carbs but would like to know if anyone knows more about what this could be. Any ideas anyone?

TIA,

Al

 

[Homosassa Troller]

Re: 96 Yamaha OB possible fuel issue

You may have an air leak into your fuel line. That would mostly happen under load. Check all hose clamps all the back to the tank, especially the one at the anti-siphon valve. That one doesn't get inspected often. Another thing you can try is to get a portable 6 gallon tank and connect its hose directly into the the motors fuel inlet. This will help isolate the problem a bit. If it runs well the problem was in your fuel system, and if you still have the problem it is motor related. Be sure to clean the small gas filter on the motor itself.

 

[alchik]

Re: 96 Yamaha OB possible fuel issue

I already tried the spare tank (forgot to mention that...). I ordered a 6 gallon and fittings. I was hoping it would run fine as it would mean the fix would most likely be easier but no, it did exactly the same thing. I thought about the load thing as that's what it does in the beginning, i.e. runs fine at 6mph but when I shoot it to 17+ it quits after a time and can only go again after priming. But, after it happens the first time it will still quit when I'm just doing 6mph back to the dock. At this point I'm going to have to dive in the engine somewhere (carbs most likely) so I'll look to the internal fuel lines and see what's up there. A casual look, all looks ok there. I even changed out my fuel pump diaphragm as the installed one looked a bit baggy. Made no difference yet again...

 

[robert graham]

Re: 96 Yamaha OB possible fuel issue

If you're having to pump the bulb to make it run, that might point to a bad fuel pump. The entire new pump is about $45. Maybe an air leak at the quick-disconnect on front of cowl? Wonder if your carb float needles are sticking closed?...then when you pump it they open up.

 

[alchik]

Re: 96 Yamaha OB possible fuel issue

yeah, I thought about that. I guess I could shoot for a totally new pump and see what happens. Worse case, I've got a spare pump I suppose. I can also replace the front cowl fuel connection as it's pretty cheap. I just hate doing troubleshooting by replacing everything it could be instead of getting to what it is (Where I guess I eventually will.)... Oh well, I've been there before!

 

[robert graham]

Re: 96 Yamaha OB possible fuel issue

I know what you mean about just replacing high price parts in hope of fixing a problem. You could just by-pass that cowling quick-disconnect with a piece of fuel hose, just to check it out. The stuck float bowl needles would be something worth checking....they can get warn and sticky. Good Luck!

 

[alchik]

Re: 96 Yamaha OB possible fuel issue

You're right about that. I'll probably have to tear into the carb anyway so might as well take it down and at least clean it. I've not been as diligent as I should be with winterizing so I could have some gummy fuel residue in there... Thanks...

 

[robert graham]

Re: 96 Yamaha OB possible fuel issue

Maybe try draining each carb onto clean white rag to give you an idea of water/trash/debris that may be in there. With drain plugs out, pump primer bulb to flush needle valves and float chambers with fresh fuel.

 

[alchik]

Re: 96 Yamaha OB possible fuel issue

Thanks! I'll give that a go!