Yamaha 3HP two -stroke problems

[whitejw]

I am trying to find out why my 3MHSR outboard won't produce enough power. It starts immediately and runs smoothly, but it produces only about 40-50% of its rated HP (we compared it to my friend's 2hp Yamaha 2 stroke and his put out twice the power of mine). Throttling up doesn't help; it just seems to make it too rich and waste fuel. We've tuned the carb but that didn't help.

We tested the compression and it was consistently at about 150 PSI. Don't know if this is normal and we need to break it open for new rings etc. Also considered the jets (maybe they're not putting out the right amount of fuel mixture?). It revs higher and produces a surge just before it runs out of power, suggesting that the mix may be too rich.

Any ideas? Your advice is greatly appreciated!

John

[robert graham]

Maybe check your fuel pump diaphragm for cracks or leaks, causing very rich mixture. Good Luck!

[steelespike]

Be sure the fuel hose is connected right,vent on tank open.
Speaking generically; try squeezing the primer bulb on the hose.If it responds to the bulb it may indicate a weak fuel pump.
Also try a little choke.If it responds to some choke it may need a carb rebuild with attention to cleaning.