whats wrong with my motor?(acts different now)

I took my boat out today and it was runnin great for atleast 15 minutes and then we were cruising just below wot when it fell on its face and died. It was hard cranking to get back started and from then on it would only run good at about 1/4 throttle. Idle was rough and if i tried to speed up it would take off but fall on its face once again. It was pissing thru all of this so hopefully it did not get hot. Runs great at quarter throttle.

Motor is a 1988 yamaha 90 hp 3 cylinder.

Any ideas and help would be greatly appreciated.

P.s. boat sat all winter and this is only our 2nd time out with it.

sounds like gunk in the carburator!

after being sat all winter, what do the fuel lines and gas tank look like?

The fuel in tank looks and smells fine but may not be. Line is a little dry rotted. It does kinda feel like bad gas except why would it be hard starting?

Did you put Stabil or Seafoam in the gas tank for the winter? This is a good warning to all the people who do not run their motors for over a couple of months with this new ethanol gas the epa is making everyone use, ya better add Stabil or Seafoam to your gas tank or your going to have major promlems.
You will probly have to change out all gas lines and squeeze bulb and have the carbs rebuilt also because of ethanol gas, it eats up the old rubber items. Go back with new gas lines and bulb with the new epa approved items. When all is done, I recommend using some kind of additive every fill up. I live on the Gulf Coast, and I use Seafoam in my gas every time I fill up. I buy mine at Autozone. Good luck with your problem, and I hope that the ethanol gas is not your problem, jus' sayin'

I did not own the boat before winter but the previous owner said that he put seafoam in it. He's kind've an alcoholic so that may or may not have happened. lol.

We dont have alot of problems in these parts with ethanol gas.
But still a good suggestion.

Yeah, I think I'll get some fresh fuel, some fresh plugs, filter, and a new line and bulb and go from there. Carbs will probably need cleaned out like you said, but there is 3 of them so hopefully that doesn't get too pricey.

On the way home the right side wheel bearing on the trailer started making a noise and its pretty loose so I keep seeing these $$$$$ popping up, but its all gotta be done.

also, what do you guys think a good WOT rpm range would be.

Just doesn't seem like its wide open when throttled all the way.

Does your boat have a fuel/water seperator on it, if not, I would install one with this new ethanol gas, lots of water in it.

Wot Rpm 5200-5500.


Carb cleaning is around 30-45 dollars per carb. I do recommend changing hose and fuel. Possibly plugs. Have you looked at the plugs yet?

how old is the fuel ilne ,if its not real gas , believe or not blended gas breaks down the inside ,even fancy merc fuel hose /. that crap gumms up the carb something fierce . don't rule it out till you check

thanks everyone.

I pulled the plugs out, lots of unburnt fuel on them.

I'm gonna get some fresh gas, new plugs, and a new line and bulb and go try it out.
I'll prolly stop by bucks outboard and see when skeeter could do the carbs

Ethanol gas is terrible for carbs and fuel systems that weren't designed to use it...(I don't think its good for those that were either). Check out this web site...you can probably find a station close to you that has non-E gas. We have a few in Montgomery.
https://pure-gas.org/
I REFUSE to use ethanol in our motorcycles, small motors, yard equipment, outboards, etc... If you HAVE to use it, use Stabil but still don't store it long. One thing I do with the dirt bikes and other small motors is shut off fuel flow and let motor idle until carb runs dry...that way the gas is not sitting in system/carb while it is stored. I really can't tell you how bad I hate this ethacrap...

New plugs, new line and bulb, additive in fuel and addditional fresh fuel, and now it doesnt die but it maxes out at 3600 RPM at WOT.

Before the isssues arrose it was running about 5100 RPM WOT and I didn't think it was ever opening all the way up.













we really do not have a big problem with ethanol around here.

We have a few stations, maybe 1 out of 10 have the ethanol in the gas.

That's good that you have new lines and fuel. I have not has Mo trouble in mo for ethanol. I still think there is something in your carb. When you check the plugs is there one that looks dryer than the others?

Also...I'm sure you already tried... But the vent on the gas tank is open right?

The two other options I would think of is the fuel lines on the motor itself. One might be dry rotted enough to suck air....

Or...


Maybe be a bad cdi box (computer). But I don't think that's the case


I think you have dirt, rubber, etc... In your carb

Be careful and get this fixed and don't keep running it. 3 cylinders run pretty good on just 2 cylinders, with one carb gummed up and not getting gas. I have seen alot of 3 cylinders with 1 cylinder down from running with 1 messed up carb and 1 cylinder not getting oil.

Flintcreek

Everyone seems to think it might be the carbs, so I pulled them off this afternoon and we're gonna clean em out tommorrow at work. The reeds look good, but I'm still considering some Boyeson carbon fiber reeds.

The carbs came off really easily. (6) 10 mm bolts and a couple of small clamps and she's off there.

I left the 3 carbs linked together to eliminate complications there.

alright, I'm officially puzzled.

Cleaned all 3 carbs out, and it runs the same.
maxing out at 3600 rpm with a rought idle

With the motor running pull each plug wire one at a time and notice if the idle changes, maybe you have a cylinder that's either not firing or not getting fuel. If you identify a cylinder then do a compression check (just to be sure) then check your coils. If all is good after that then it's probably a carb issue....ethanol is evil.

My motor did exactly what yours is doing . I had the carbs checked and fuel lines not it :evil: . Changed the powerpack and plugs, not it :evil: , changed the coils and plug wire not it :evil: , ordered the trigger and stator and changed both while the flywheel was off and whala it was one of them 2 =D> =D> :mrgreen: , not sure which but it runs like a top again. I understand there is a very simple test for this that a good mechanic can do, but I just went by process of elimination and now have a brand new electronic system good for another 20 years hopefully. [-o<

I think I found the problem,

cylinder 1 has 120psi
cylinder 2 has 0 psi
cylinder 3 has 125psi

:evil: