1992 evinrude 10hp question

[Baby Blue]

starts and runs very good but after running full throddle for a while it will start to loose power. example... if I run full throddle with a cool engine the boat will go about 12mph but then slow to about 8-9mph as it warms up. Usually takes about 5 minutes of open throddle to start slowing down.
Doesn't seem to be running hot but I thought it might be a thermostat?
any thoughts? It does have a 15hp carb but it was brand new when installed. Guessing 150 hours on engine.
thanks, BB.

 

[Daviet]

Re: 1992 evinrude 10hp question

Will pumping the primer bulb help?

 

[Baby Blue]

Re: 1992 evinrude 10hp question

Pumping the ball didn't help. All I can find it that it seems to do it after it's warmed up.
BB>

 

[Baby Blue]

Re: 1992 evinrude 10hp question

I thought about pulling the thermostat and seeing if that helps. Maybe it's not opening all the way? Any other ideas would be greatly appreciated.
thanks, BB

 

[Marvxyz2]

Re: 1992 evinrude 10hp question

You might check out your electrical components.

 

[Rick.]

Re: 1992 evinrude 10hp question

Sure sounds like a failed/failing coil. When it is not giving good speed (coils warm) do a spark test. Best of luck. Rick.

 

[steelespike]

Re: 1992 evinrude 10hp question

Check the plug might be the wrong heat range.If you and the boat aren't too heavy the speed should be around 20 mph. A 5hp is rated for 12 on a light reasonably fast boat.

 

[Baby Blue]

Re: 1992 evinrude 10hp question

thanks. I'll check the plugs and coil. it's a heavy fiberglass 16' boat with 2 people so it's never gotten over 12mph or so.
thanks again for the info.
BB

 

[steelespike]

Re: 1992 evinrude 10hp question

If the boat and load are heavy and it is propped wrong plugs could be heating up from lugging? Bad for the motor.Cooler plug might help but you may need to go with a lower pitch prop.