[gmarshall43]

I have a 1964 Evinrude, 6hp. It will start up and idle fine. It will run good in gear at low speed but when it has runned at full throttle for a few minutes it will began to slow down. I took the cover off while it was running and it began to run faster. I put the cover back on and it slowed down again. I thought this might be heat related but the water pump is spitting out water well. Any suggestions?

Thanks

[ftltony]

Leave the cover off!!!!

Look for the "vent holes" on the cover, sounds like they are blocked.

[Xcusme]

Classic symptom of a leaking exhaust gasket allowing exhaust to foul the fresh air into the carbs.

[F_R]

Even more classic symptoms of somebody running it in a barrel. Are you?

[ftltony]

Originally Posted by F_R

Even more classic symptoms of somebody running it in a barrel. Are you?

Explain that one......? I have run motors in barrels and never experienced this.

[clemsonfor]

Agree with both most likely a blown exhaust gasket or blocked air passage. Running in a barrel at WOT or near it makes lots of exhaust and with the motor not moving it boils out from around the motor and clouds around it so even if sucking air right it sucks exhaust.

-nate

[gmarshall43]

yes I am running it in a barrel. I will be running it on a lake this next week. I'll be sure to check the exhuast gasket.. thanks

[F_R]

Breathing even a little bit of it's own exhaust smoke has a drastic effect on performance. The air intake is below the cowling so it is just like sticking it's nose down into the barrel. With the hood off it can breathe air from higher up.