how to extend a drive shaft?

mrkeith · #1 (**permalink**) 02-23-2007

hi, i just bot a new folding prop and when i went to put it on, it seems that the threaded part of shaft is too short for the nut on my new prop, and that the distance between my old prop and the strut probably will prevent me from rethreading and extending the threads on the shaft any further to accomodate the new nut. short of buying a new, longer shaft and rethreading it, any suggestions on what to do? i think i need about an inch or two is all. thanks for the ideas/suggestions

cheers

Idiens · #2 (**permalink**) 02-23-2007

I have seen spacing blocks inserted between the gearbox and the shaft connector to win enough length to fit a rope cutter. Maybe that trick will work for you.

Valiente · #3 (**permalink**) 02-23-2007

Quote:

Originally Posted by Idiens

I have seen spacing blocks inserted between the gearbox and the shaft connector to win enough length to fit a rope cutter. Maybe that trick will work for you.

You might be able to add a pair of Drive-Savers (consult a mechanic on this, though, because I don't know if they can be doubled up). The added benefit, of course, is reduced vibration. Whether or not you'll interfere with your stuffing box is another issue.

http://marineengineparts.com/shopsit...ml/page90.html

Faster · #4 (**permalink**) 02-23-2007

If the new prop is landing on the shaft taper but the threads are still too short pushing the shaft out at the coupling won't help.

If the new prop is hitting the strut before you can get the nut on then it isn't even on the taper. In this case if you have the room you should be able to do as Valiente suggests.

Otherwise I think you're into a new shaft - I don't think I'd trust a welded extension. Also you might check that the tapers actually match.

pigslo · #5 (**permalink**) 02-23-2007

I put a new shaft on my boat and added a flexible shaft coupling. The new shaft was 1 1/4" shorter than the old shaft.
pigslo

mrkeith · #6 (**permalink**) 02-23-2007

whats a flexible shaft coupling?

pigslo · #7 (**permalink**) 02-23-2007

The poster above Valiente refered to it as a shaft saver. I bought mine from http://www.flexible-coupling.com/
pigslo

mrkeith · #8 (**permalink**) 02-23-2007

Quote:

Originally Posted by Valiente

You might be able to add a pair of Drive-Savers (consult a mechanic on this, though, because I don't know if they can be doubled up). The added benefit, of course, is reduced vibration. Whether or not you'll interfere with your stuffing box is another issue.

http://marineengineparts.com/shopsit...ml/page90.html

drive savers look pretty expensive. i mean how much would a new shaft cost i wonder? all they are are long metal rods right?

pigslo · #9 (**permalink**) 02-23-2007

I believe I went to a small machine shop and was charged either 200 or 250 dollars.
pigslo

mrkeith · #10 (**permalink**) 02-23-2007

i guess i ll do the same today and see what they suggest. how hard is it to take out the shaft in order to bring it to the machine shop ? is it a big drama?
thanks for the help btw