Bent Prop Shaft

[Bill Jenks]

Hi All

I hauled Unzipped (2000 Mark II, Hull #1484)today to give her a coat of bottom paint. Upon inspecting the prop shaft I discovered it is bent. When I spin the prop by hand I can see a wobble in the propeller end of the shaft. It appears to be bent just aft of the strut. The wobble is about 1/8 inch. I talked to the yard guy and he confirmed that it was bent and asked if I noticed any vibration. I do not. He suggested leaving it until I notice a problem and then replacing the shaft with a SS one.

It seems to me that a bent shaft even if it is not producing a noticable vibration would have to be putting unusual stress on the strut, cutless bearing (which seems OK), transmission, bearing, etc and could eventually cause some serious damage.

Does it seem reasonable to not repair it until later as the yard suggested or am I better off replacing it now?

Thanks
Bill Jenks

[hdevera]

Why wait until something bad happens?  Besides the cost of making this repair, you'd have the additional cost of having to haul your boat out of the water again.  In addition if you wait, the problem could surface at a time you least want it to happen.  If you can see the problem so easily, you can be sure it will be noticeable IMHO.

[Roc]

I agree with Hal, get the ss shaft now that your boat is hauled.  You may also consider having your prop re-conditioned.  Something had to happen to bend the shaft, and maybe your prop blades could be out too.

Roc-

[Mike Smith]

"An Ounce of Prevention is Worth a Pound of Cure". Hey, I like the sound of that! Do it now.

Mike

[Kyle Ewing]

I had a similar experience.  My cutlass bearing needed replacement so I had the prop and shaft checked out when off.  The prop was out of balance and had a slightly bent shaft (maybe from removal, can't be sure) even though I had no vibration.  

With a new shaft and reconditioned prop, it is still as smooth as before, but I have noticeably more power, half to a full knot more at 3300 rpm and 6 knots at 2700 rpm (up from 3000 before).

The condition certainly won't improve and will probably get worse.

Kyle Ewing
Donnybrook #1010
Belmont Harbor, Chicago

[tassber]

Is it possible that your shaft was bent during the haulout with the sling too far aft?  I saw this happen to the boat ahead of mine at the yard and decided I would always be present during the haulout.  Just a thought.

[Bill Jenks]

Hi All

Thanks for the advice. I have decided to replace the shaft and have the prop looked at by a prop shop just to make sure it is not bent too.

I was present at the haul out so I know that the yard did nothing wrong.

Thanks again for the help.

Bill Jenks

[Bill Jenks]

Thanks for the ideas Ron.

I am going with a stainless shaft and plan to replace the cutlass bearing too. I will check the article you wrote and consider repitching. I do have the factory installed 3 blade. What pitch do you recomend?

[Bill Jenks]

A quick update.

Unzipped went back in the water yesterday. I replaced the prop shaft with a stainless one. I also replaced the cutlass bearing.

I did not notice any vibration while motoring before this work but it had to be there. Now, while motoring, it is noticibly smoother than before.

I decided not to re-pitch the prop at this time but to save my pennies for a folding or feathering prop next year.

Thanks for all your advice.