Cavitation or spun prop ?

[Lund_bC]

Hi, Just trying out my new boat (older 40hp johnson motor on 15ft boat), when on a nice run today and everything was going great on the way for about 45 min.

On the way back at higher speed and rpms, It felt like a slipping clutch in a car where the rpm of the motor would shot up but the boat wouldn't speed up maybe even slow down a bit.

We kept going for a while, I stopped and put in reverse and at that time a stick about 1 foot long and 1 inch diam came floating up and me and my buddy were wondering if that just came out of the motor area

So anyways we drove home for another 5 min and no more of the slipping clutch feel, it was running really good.

Someone at the dock was saying Cavitation and someone was saying maybe a spun prop.

I don't see how a stick could even get caught up there and stay on at high speeds, but i see how a stick could cause these air bubbles.

I am kind of wondering if it might be a spun prop, because that would leave me stranded next trip maybe if I don't fix it.

Is there anyway for a spun prop to start acting up and then the symptoms go away for some reason ? Or do they just blow when they blow, I would like to rule out the spun prop before I take off on another cruise.

Thanks everyone !

 

[Will Bark]

Re: Cavitation or spun prop ?

Put a mark on the hub and one on the prop lined up and then run it until it slips then see if the marks are still lined up; if not then the prop is spun and needs to be rehubbed at a prop shop or get a new one. Good luck.

 

[Chris1956]

Re: Cavitation or spun prop ?

Once you have spun a prop, it will not get better. If you came home at planing speed, the prop is good. Maybe the stick and other stuff interfered with water flow to the prop.

 

[jimmbo]

Re: Cavitation or spun prop ?

Since it ran better after the stick made its appearance, I would say the slippage/rpm surge was a result of interuption of waterflow to the prop

 

[boobie]

Re: Cavitation or spun prop ?

I'd say the stick had a lot to do with it as long as it ran good after.

 

[D.spencer]

Re: Cavitation or spun prop ?

I would say to take the boat out and put the stick right back where it was and see if it does it again. It's the only way to know for sure....:facepalm::facepalm::facepalm:

 

[Lund_bC]

Re: Cavitation or spun prop ?

I would say to take the boat out and put the stick right back where it was and see if it does it again. It's the only way to know for sure....:facepalm::facepalm::facepalm:

I couldn't find the right stick to have a look, so we stuck a pack of hot dogs inbetween the motor and the boat, and all that seemed to happen was chopped up hot dogs, so I have my doubts still.

 

[D.spencer]

Re: Cavitation or spun prop ?

Is that how beenie-weenies are made ???