Yamaha 250 HPID rapid RPM uncotrolled increase

[lendebr]

My Yamaha 250 HPID 2004 experiences a rapid uncontrolled increase in RPM at about 2500 RPM. Boat slows. I can operate at about 10 knots or so without this problem occurring.

Can anyone advise me of possible causes?

 

[seahorse5]

Like the others also said, spun prop is likely or something causing it to ventilate suddenly.

 

[boatguy823]

Re: Yamaha 250 HPID rapid RPM uncotrolled increase

sounds like a spun hub in the prop to me

 

[lendebr]

Re: Yamaha 250 HPID rapid RPM uncotrolled increase

Thanks for your replies. Since the boat's forward motion stops with the increased RPM, is it more likely a spun hub? If so what is a spun hub? Is it a matter of replacing the prop?

 

[robert graham]

Re: Yamaha 250 HPID rapid RPM uncotrolled increase

props made in 2 parts, inner hub and outer part with blades, held together with rubber to give some flexibility if you hit something. the rubber(like the clutch on a car) has failed and the outer part with blades is just spinning free. there are "prop places" that can rebuild it with new rubber or you can just buy a new one. Good Luck!

 

[lendebr]

Re: Yamaha 250 HPID rapid RPM uncotrolled increase

Well, it was a spun prop. I opted to purchase a new one, replaced it and went fishing. It is a wonderful life, new prop and two nice rock fish.

Thanks for all of the responses and helpful information.