Yamaha 115-2 stroke--bogs down

I have a 1998 Yamaha 115 outboard 2 stroke that runs great on dry land. When you put it in the water--it idles great, but will not rev up and run as it used to run. It does great on dry land when you rev it up but not under load.

It has been in the shop for 2 years and the mechanic has replaced about everything electrically on the boat and has redone the carbs and gas lines. He is a great guy and has given up on the motor. He says that the Yamaha factory rep says the problem is a cylinder sleeve.

From the bill he has reworked the carbs, replaced the fuel hoses, installed a new CDI unit, Staton assembly, replaced the pump, fuel separator, Pulsen Coil Assembly, crank start key, pressure relief valve assembly. etc.

He says that the motor has good compression and spark.

When I returned home with the boat--I cranked it and it idled well and ran fast when I put it in gear after connecting water etc.

This motor has less than 100 hours on it and has never given any trouble before our fishing trip 2 years ago.

Any suggestions or ideas?????

What he's saying doesn't add up to me. If there's an issue with a cylinder sleeve, that would mean you'd have low compression. Try to find the service manual on yamahapubs.com and do a compression test yourself. The gauge is not expensive and it's an easy test to perform. The service manual will tell you what the minimum compression for your engine should be.

During this test, you should also inspect the spark plug tips. If they're black and wet, you know that engine oil is leaking somewhere and coating the plugs with oil. If they're dry and dark, you know it's running rich (too much fuel in the air/fuel mixture going into the cylinder). If they're orangey/gray, that means it's running lean (too much air in the air/fuel mixture).

If you do find that it has low compression in one or more cylinders, it's probably time to get a new engine, as the cost to repair it would be more than it's actually worth. Given that he already worked on the carbs, I would guess it's low compression.

It's possible that it could be a spun prop hub, but in that case, it would still rev up under load. You'd still feel the power loss, but the RPMs would still go up.

If you're not comfortable doing the compression test, take it to someone else.

It could be the carbs given all that has been done. Cleaning those carbs can be very difficult if they get gummed up. If he cleaned them by hand and didn't have an ultrasonic cleaner tank etc there is a chance that they haven't been cleaned enough. If you have good compression and he has been right through the spark as it appears then it is back to fuel. Since he has done the pumps (how many) you come back to carbs of maybe the spark advance but he should have got that sorted if it was wrong.

Carbs have not been properly cleaned.All the ignition parts you have replaced are parts that very rarely fail. Having sat so long I am guessing one or more of the main nets have a thin layer of varnish making the jet fractionally smaller, that is all it takes.