[WahooYeah]

Bought a 1987 16' Wahoo with a 70HP Yamaha about a month ago and haven't been able to get it running right since. A bit of history: When I bought the boat, I tested it on the trailer with muffs using fuel from the built-in tank. It seemed to run fine and I had good, even compression across all 3 cylinders.

After towing it, I evidently stirred up all the junk and water that was in the fuel tank and tried to run the motor. I must have filled up the carbs with crap and it wouldn't run anymore without choke and full throttle. I emptied the built-in fuel tank and haven't even tried that tank since. I bought a portable 6 gallon tank and am using new gas. Had the carbs cleaned and reassembled by a mechanic using new carb kits. Changed the plugs, fuel filter, rebuilt the fuel pump using new diaphrams and gaskets, and changed all the gas lines from the tank to the motor.

Now the motor starts and runs great on the trailer with muffs. When I put the boat in the water, however, it goes like a bat out of hell for about a minute and then bogs down and refuses to rev past 2100 rpm.

Could the carbs need further cleaning? Since it runs fine on land and briefly in the water, I am totally confused.

Thanks for your thoughts and suggestions.

[dashmore]

I have a 70 hp Yamaha,go about 5 pages of threads back to 70 yama no power under load,mine did same thing had carbs rebuilt and new fuelpump installed with tune up and now it is fine.

[Yamajoe]

Could be airleak in fuel system, clogged filters, fuel pump, low oil; is it overheating?

more likely carbs, jets esp high speed jets picked up gunk again, clean your carbs, redo the link and sinz and check the timing as this motor is finicky at WOT timing.