Balancing a Sailboat Prop ?

[ribbony]

The prop we have is quite old but looks in good condition apart from a small nick on one blade. I was wondering how critical balance is to a sailboat prop ? If it is does it really need the $190 balancing that I was quoted over the phone by a well known Sydney prop specialist

PS: it is a fixed blade bronze prop on a 35' steel yacht with a 30hp diesel 3600rpm max.

[KestrelBuck]

If the propeller is not balanced then it will vibrate. If it is vibrating then it will work the shaft in the cutlass bearing, causing that to wear. If the shaft is being worked by the propeller then there is also the risk that it is causing undue wear at the stuffing box. And, in the worst of all possible worlds it could also wear out the transmission bearings.

The propeller should not chip if it is in good shape. Electrolysis can leach alloys out of the prop, weakening it and making it brittle. If at the chip the prop looks a bit reddish then electrolysis is suspected. When you brush or scratch the body of the prop it should come up bright if it is in good shape.

[ribbony]

Thanks, I will have a close look at the prop. Ummmh, never tried to use a magnifier underwater, but this looks like a good time to try it.

[barnakiel]

If it vibrates at all revs, it may be the prop out of balance. Then often there will be more vibs as you rev up. A minor nick will not unbalance a big prop. But if the missing portion is not minor or if there is also any deformation around it, I would pass the prop to the shop.

New props are not very expensive (unless folding/feathering) so balance the shop quote against a quote for a new prop if you have any pricing doubts.

b.

[ribbony]

It is a very small nick, the prop is OK otherwise, but it was installed in 1983 and like the rest of the boat, suffered neglect. I can probably find a secondhand prop in better nick for about the tune up price.

I am trying to eliminated possible problems for when we put new cutlass bearings in at the next slipping.

[mbu745]

All good, but HOW you balance a propellor yourself please?

[GordMay]

Originally Posted by mbu745

All good, but HOW you balance a propeller yourself please?

I'm afraid, you don't.

[bobconnie]

Im sorry but you can't balance a prop without the proper balanceing machinery!! this type of equipment is expensive. We are lucky as we have a bunch of prop shops down here near the Gulf so reworking and balencing are some cheaper then the price you got there ! but thats life I guess! down here we would get a full rework and balance for the prices you were given ! but ya gotta go with the prices they charge! can ya get any other bids ??

[Jim Cate]

G'Day Ribbony,

I gather that the prop is currently on the boat and in use. If that is so, you should be able to tell if there is unacceptable vibration by... well, feeling things whilst underway at various speeds! If it isn't vibrating too much, why worry? If your cutless bearing has lasted through a reasonable period of use there is likely not an issue there either.
If it has perished too soon, well, maybe the balance is indicated, as well as a check of the straightness of the shaft.

Hope that you can get it sorted without getting rooted by the prop bandit!

Cheers,

Jim

[Ozbullwinkle]

Hi ribbony,

I've had props serviced in the past (twin screw diesel powerboat) by Austral propellers in Sydney and was happy with their work so if thats not who you got your quote from maybe they might be worth talking to for another opinion.

[Blue Stocking]

IMHO, I think a lot depends on your drive set-up. A correctly balanced prop is, of course, the ideal.
I cruise at an engine speed of 1800-2000 rpm, turning a 3 blade 17 x 13 thru a 2:1 hurth HBW 150 box.
I hit a log on 1 occasion which, I later discovered, had curled 2" of one blade.
I motored a number of times that weekend with absolutely no vibration, and no damage to bearing or shaft.
Jus sayin.