1994 - 90 HP Yamaha 2 stroke

[freeride]

I have a 1994 90 HP Yamaha 2 stroke. No mixing of fluid its injected. Started having trouble where it would not run full out. Mechnanic said it was bad gas. Removed gas, had 100 hour service. Launched, boat would idol but not get up on plane. Took back to mechanic. Mechanic said it may be plugs... Took it out it would idol, run at 3800 rpm but never full out. Lost faith in mechanic. Took it to where I bought it. Mechanic overhauled carbs, replaced spark plugs. Would Idol fine, get up on plane then it acts as if someone takes the prop right off of it and it stalls. He is now saying it is the fuel pump (possibly). Bulb stays tight.

P.S. The boat would run full out at the dock but under load it fails. It will taxi all day up and down the channel but I do not typically drift fish in the channel

 

[robert graham]

Re: 1994 - 90 HP Yamaha 2 stroke

Sounds like a fuel pump problem. Check it out and replace it if required. If you're running along at 3800RPM's and you pump the primer bulb and the motor gains RPM's and runs better then it's almost surely the fuel pump. Good Luck!

 

[99yam40]

Re: 1994 - 90 HP Yamaha 2 stroke

what does" acts as if someone takes the prop right off of it and it stalls" mean?
The prop slips and motor RPM goes high and then dies?
No motor should be run full out at the dock with no load on it, ever

Check fuel system on both sides of pump with a fuel pressure/ vacuum guage. it will tell you if there is a restriction and if the pressure is good. Use a piece of clear tubing and it will show if you are sucking air from somewhere.

http://forums.iboats.com/showthread.php?t=283363