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-   -   Changing prop underwater (http://www.sailnet.com/forums/gear-maintenance/27579-changing-prop-underwater.html)

trantor12020 01-08-2007 12:26 AM

Changing prop underwater
 
I've just ordered a new Campbell Sailor prop and is thinking of doing the swap underwater (with scuba gear of course). I've thought through the work processes and tools needed (bag to hold clotter pin, spanners, 2-claw bearing-puller<for removal of old 2-blade>, hammer, shaft-key ...).
Any advise from those experience in this ? e.g. should I engage into gear to lock the shaft when doing the swap? ..can hammer the old prop hub to free it? will the new prop go in freely or require some effort? should the prop shaft hole be grease? etc...

Ken
h326, SV Millennium 2
Singapore

Faster 01-08-2007 12:37 AM

I'd say definitely lock the shaft - you'll have enough difficulty using the puller underwater as it is.

I'd suggest you tie something on the old prop - they can "pop" off the shaft with some force and it might go for a swim if it turns out to be on real tight. Maybe leave one nut loosely on the shaft as a preventer....It's a good spare. When you use the puller stay to one side - don't be in the line of fire.

You might give the end of the shaft a good smack once the nuts are loose - this may pre-loosen the taper fitting, but use a soft hammer or a brass drift so as not to damage the threads.

The new prop should go on easily if everything is clean. Some never-sieze shouldn't hurt.

Since its a 326 it hasn't been on there for 20 years, so things should go OK - but it's a much easier job to do on the hard.

trantor12020 01-08-2007 12:44 AM

THANK YOU ! didn't occur to me to tie the old prop. Will do.

jones2r 01-08-2007 01:32 AM

Once the puller has tension on the prop, tapping on the shank of the prop will break the corrosion between it and the shaft. Light tapping for a slightly prolonged period is best; you're breaking corrosion, not rearranging the metal. Place the retaining nut flush with the end of the shaft (protects the threads) and give the end a whack while under tension. If it doesn't come loose, put more tension on the puller and resume tapping on the prop.

cardiacpaul 01-08-2007 09:46 AM

you;'ll also need another pipe wrench to put on the prop shaft to prevent it from turning. Form experience, I've found that putting it in gear won't help. (much)

trantor12020 01-08-2007 09:57 AM

Quote:

Originally Posted by cardiacpaul
you;'ll also need another pipe wrench to put on the prop shaft to prevent it from turning. Form experience, I've found that putting it in gear won't help. (much)

hmmm, ok, I'll consider that. I assume you mean that when push-comes-to-shove the prop will turn even if its in gear. two spanners, a pipe wrench, puller and a prop, I don't think I'll need much weight to be negative buoyant.
Thanks for the info.

bmunse 01-08-2007 10:08 AM

Please don't put a pipe wrench on the prop shaft. I normaly use a 2x4 or other wood block and put it between the blades and the cutlass or blade and the hull. I applaud your drive to change prop without a pullout. Try to have someone at hand who is experienced in changing props. ps putting any modern marine transmission in gear without the motor running will have no effect on the prop shaft turning as they are hydraulic transmissions. Like the automatic in your car.

trantor12020 01-08-2007 10:19 AM

bmunse, when I sail, to prevent the prop from spinning (and making noise) I put it in reverse gear. that holds it from spinning. so I assume this would in some way prevents the shaft from turning as I loosen the nuts. I'll be doing this underwater with scuba ...alone.

jones2r 01-08-2007 10:51 AM

Even if you are able to lock the transmission, you'll be able to turn the engine over; the starter motor can. Be a hell of deal if you were able to start it!

Faster 01-08-2007 12:11 PM

By alone I hope you mean you're the only one in the water - but that you will have a buddy on the boat/dock to assist and monitor your safety.

Some transmissions will lock the shaft, but only to an extent as Jones indicates. The pipe wrench is a bit brutal but will avoid stressing your strut if you need to put a lot of torque on the puller. Blocking the prop against the aperture or hull may transfer the forces to the strut.

Tapping the shaft with the puller tensioned is a great idea.


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