Prop spins, boat doesn't move

[OSGFII]

The propellor on my friend's sailboat spins, but the boat won't move. I just cleaned the prop off, so fouling on the prop is not the problem. I'm not sure it's the right size for the boat/motor, but it used to work. There is some growth on the hull, but not coral heads or anything (to my point of view) particularly substantial. Ideas to make the boat go? What am I overlooking?

 

[jspansel]

Re: Prop spins, boat doesn't move

Score it and hub, is the prop slipping?

 

[QC]

Re: Prop spins, boat doesn't move

The propellor on my friend's sailboat spins

What type of motor/engine setup? Inboard auxiliary with a Folding prop? Outboard "kicker"? Need a little more info.

When you say the prop spins. What do you mean? Can you see it spin in the water and in gear? If it only spins out of the water, but not in, then I am going to assume this is an Outboard and then I would agree, spun hub. If you can see it spin in the water, and see the prop speed accelerate in the water, then I would suggest you need to untie the boat from the dock . . . Kidding . . .

 

[steelespike]

Re: Prop spins, boat doesn't move

Tell us what the setup is outboard,inboard,inboard with reduction.Does it go in reverse.
Is it a folding prop? If an outboard; the hub may be spun. Put a water proof mark acrose the underside of the prop,test run and check the mark allignment.

 

[OSGFII]

Re: Prop spins, boat doesn't move

It's an inboard diesel. I'm not too knowledgeable about inboards; I guess I need to research reduction (I don't know about the transmission at all).
I can see the prop spinning in the water. Same symptoms for forward and reverse

 

[chrome dome]

Re: Prop spins, boat doesn't move

1. untie the mooring lines
2. lift the anchor.
3. get a bigger motor
LOL
sorry.. couldn't help meself
now a helpful answer, l agree with the others
it does sound like the prop is slipping

 

[QC]

Re: Prop spins, boat doesn't move

It's an inboard diesel.

I can see the prop spinning in the water.

This doesn't sound like a spun hub since inboard propellers don't have hubs . . . Does the prop spin faster with RPM? Still doesn't go at all? You may have to rev pretty high depending on the size of the boat.

 

[steelespike]

Re: Prop spins, boat doesn't move

I can't speak for todays straight drive transmissions but usually they are a planetary
gear set (gears allways meshed ) One clutch locks up the whole gear set for forward the other locks up only the gear carrier to produce reverse. I think some transmissions have hydraulic actuators Istead of a direct mechanical connection to the clutches.
Maybe a malfunction of the actuaters or hydraulic circuit would cause the clutches
to not engage.There is a very slim chance the prop shaft has slipped out of the coupler at the transamission just far enough so the key is no longer engaged (not likely)
This did happen to me years ago but the shaft just came all the way out in reverse
and was stopped by the rudder.
It just occured to me that this may have a hydraulic drive like you find on upscale garden tractors and zero turn lawnmowerers.

 

[Part-time]

Re: Prop spins, boat doesn't move

It just occured to me that this may have a hydraulic drive like you find on upscale garden tractors and zero turn lawnmowerers.

If it is a hydrostatic drive it might just be low in oil.

 

[QC]

Re: Prop spins, boat doesn't move

This is why I asked if he can see it spin in the water, and especially if he can see it accelerate (the prop). If so, then the tranny is at least doing something.

 

[OSGFII]

Re: Prop spins, boat doesn't move

Thanks for all this info. I'm going to print it out next time I visit the boat and see if I can figure something out.
Aloha,
Derek

 

[tpenfield]

Re: Prop spins, boat doesn't move

Given the array of things suggested, I'll go with . . . the boat is still tied to the dock/mooring. Untie it and you will be on your way

 

[cyclops2]

Re: Prop spins, boat doesn't move

Someone forgot to put the key in. It locks the prop to the shaft. OR The key has broken.

The key is broken or missing at the other end of the shaft.

Worse. Both keys are missing & or broken.