Early 90's Yamaha 85 hp

[dickjustice]

I recently purchased this motor to replace a 75 hp force that had a cracked block for a 25 ft pontoon boat. A shade tree boat mechanic found the engine for me and I let him install it. Of course I was assured that the motor would run fine, but when I took it out for a test drive the new to me motor did not seem right. First, the motor cranks and idles like a champ and accelerates to half throttle fine but when I continue on past half throttle there is not a difference in performance. I checked the throttle linkage to make sure that it was opening up the carbs past half throttle and it seemed to be operating fine. Needless to say, but I was very dissappointed when the new motor with 10 more hp was actually slower than my old motor only running off of 2 cylinders. I am going to change the fuel filter this week and run a can of seafoam through it. Anybody got any ideas where I should start checking if its not the fuel filter. It seems to me that its not getting enough fuel.

 

[renegade15]

Re: Early 90's Yamaha 85 hp

Carb clean, you'd hate to toast a cylinder. Check for spark on all three cylinders and proper timing advance as well.

 

[shackle101]

Re: Early 90's Yamaha 85 hp

My 93 yahama had a similar issue. It turned out to be the gas line so be sure to check that for blockage. Mine would gain speed then just slow down I thought I was the linkage as well. Could also try some seafoam, but if the crabs are gummed up bad you will need to rebuild as mentioned above.

 

[99yam40]

Re: Early 90's Yamaha 85 hp

As they have already stated, if it is running lean because of fuel problems and you keep running it , you will smoke a piston and kill yet another motor. Troubleshoot and fix it properly