Yamaha 2-stroke 50HP 1980's bogs and not reaching max RPM

[1up]

Many pumps are mounted directly over the PRESSURE pulse port.

Ok will check for that.

 

[1up]

Fuel pump checked. It didn't let out any fuel through the port. Found the spring seat and got the pump back together.

Next test for spark but the main battery switch is lost so ordered a new one Gotta luv it.

 

[1up]

Today's session with the motor points to overheating. Could drive the motor for longer without it losing rpm and it is colder in the water and ambient temp too. Both screws to the thermostat housing broke so will drill them out and then replace t-stat. Will go through all carbs and clean them too. Maybe drop the LU and change the eater pump for good measure. Next weekend is boat pickup weekend so this one is going to be concluded season 2024.

Thank you all for your help to nrrow down the problem sources, and happy boating. We live and we learn.

 

[1up]

A new boating season and a new update.
T-stat replaced, and carbs cleaned. Cyl #3 one was basically all clogged up. Cyl #2 was partly dirty.

Hope to provide an update in a couple of weeks time with the boat in the water.
At idle it goes fine now.

 

[99yam40]

sounds like you are making headway

 

[1up]

Thanks, yes indeed. Can confirm engine runs strong now after t-stat replacement and carbs being cleaned out.

The kicker was the autolube-dispensing is either faulty or may need some time / air bleeding. Luckily premixed the fuel to be on the safe side.

Thanks all for your help and wish everyone a great boating season.