RPMs Increase but No Increase in Speed?

[njm_T160]

Greetings All,

I have a 1998 40HP Tracker/Force on my 21' Pontoon boat. I have noticed that when I open it up above 3500 or so, the RPMs will suddenly shoot up about 600-800 RPMs "by itself." There also seems to be no increase in actual speed when ever this happens. I usually just back down the throttle a bit to get it back the the original RPM range I was going for. The motor seems to be running fine at all other times and starts great (knock on wood).
Is this normal????

Thanks,
Nels

 

[foodfisher]

Re: RPMs Increase but No Increase in Speed?

Increase in rpm's with no increase in speed is usually a spun prop hub.