Spun prop symptoms

[Bill kubiak]

I have a merc 15 on a 12 ft boat. I give it the gas and I get up to 7mph then suddenly the motor revs, surges, and goes no where, I ease off the thottle and it goes nice and smooth again at around 7 mph.

How can I be sure the prop hub is spun out????????

Could this be another problem????

 

[Barnacle_Bill]

Re: Spun prop symptoms

It certainly sounds like a spun hub. To check it make 2 marks opposite each other on the inner and outer hub. Then try it again. If they are not lined up as marked then the prop needs to be re-hubbed.

 

[Bill kubiak]

Re: Spun prop symptoms

Is there a way to check it without dragfging the boat all the way to the dock?

 

[TilliamWe]

Re: Spun prop symptoms

You could remove the prop, and the hub *might* look bad. But realistically, testing as stated above is the best way. You could also bolt on another identical prop and run it. Either way, you're gonna have to water test it to be sure.

 

[Bill kubiak]

Re: Spun prop symptoms

Just more dumb questions. Is there a clutch or something in the lower unit that could be slipping and making it appear the hub is spun out??????.

The motor was sitting unused in a garage for the last 5 or 6 years, I was wondering if the rubber in the hub can deteriorate from sitting?????

 

[Barnacle_Bill]

Re: Spun prop symptoms

Just more dumb questions. Is there a clutch or something in the lower unit that could be slipping and making it appear the hub is spun out??????.

The motor was sitting unused in a garage for the last 5 or 6 years, I was wondering if the rubber in the hub can deteriorate from sitting?????

Rubber can dry rot from sitting.

 

[Bondo]

Re: Spun prop symptoms

Just more dumb questions. Is there a clutch or something in the lower unit that could be slipping and making it appear the hub is spun out??????.

Nope,............

 

[Bill kubiak]

Re: Spun prop symptoms

Miami Propellor Re-Hubbed the prop, they said it was totally shot. Have not had a chance to try it out yet, things keep taking priority

 

[Silvertip]

Re: Spun prop symptoms

Yes -- there is a "dog-clutch" in the lower unit that engages and disengages the prop. But that's not likely what the problem is. When the edges of the dogs get rounded off -- usually because the operater "slides" the unit into gear rather than "snapping" it into gear, the clutch will chatter as it engages and disengages. I too feel you have a spun prop. Or the engine is mounted too high on the transom and the prop is ventilating (losing its bite). If you have a short shaft motor on a boat that has a 20 inch transom, that's also an issue.

 

[mickjetblue]

Re: Spun prop symptoms

Another test you might try is to see if you can turn the prop
by hand with the motor not running.

Put the motor in gear, with the motor not running.
With your hands, you should be able to turn the prop one way,
but not the other way. If you can easily turn it one way, that is fine.
Apply a little more torque by hand to try and turn it the other way.
If it turns, and feels like it is actually slipping, then the hub is slipping.
This is not totally foolproof, as the hub has to be pretty well spun out
for you to be able to turn it by hand. It's worth a try, anyway.
Good luck.