prop shaft engine flange

Designs for inboard or outboard power

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Brian
Posts: 194
Joined: Mon Feb 18, 2013 10:06 pm
Location: Hawaii

prop shaft engine flange

Post by Brian » Sat Oct 20, 2018 12:50 pm

I have the engine end flange on the shaft, with the key in place. The flange also has two large set screws. My understanding is that the set screws are mainly to keep the shaft from departing when in reverse, and that the fit of the flange bore and the key are what transmit the torque. My plan is to wait until I have fit and bolted the flange to the transmission flange before drilling the divits in the shaft for the set screws (which will also allow me to move the flange a little along the shaft if necessary when fitting the engine). But this will require careful drilling of two 1/4" X 1/8" deep divits in the shaft, at the bottom of the 3/8" set screw holes. Should be doable with minimal damage to the threads, but I think I'll need a carbide bit to get into the shaft. Anyone got any thoughts on this before I do the undoable? Thanks.

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Roberta
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Location: East Troy, Wisconsin

Re: prop shaft engine flange

Post by Roberta » Sat Oct 20, 2018 2:10 pm

Get a bushing that fits in the set screw holes and drill smaller pilot divits. This will protect the threads in the holes. Then you can deepen the marked divits on a drill press.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Brian
Posts: 194
Joined: Mon Feb 18, 2013 10:06 pm
Location: Hawaii

Re: prop shaft engine flange

Post by Brian » Sat Oct 20, 2018 2:34 pm

The bushing is a great tip I will use. However, it would be difficult, but not impossible, to pull the shaft out and use my drill press to finish it. The flange is set on the shaft using heat to expand it, and the engine is not in yet (so I can't use the engine flange as a puller). Once the engine is in, I could mark the holes, as you suggest, and then use the engine flange to pull it off. But it's going to be tight in there to use a torch. Maybe I should rent a flange puller and do it now, while it's easier.

Alternatively, I wonder if I could successfully drill the divits in place with an electric drill and a carbide bit, using a bushing to protect the threads?

You're always "there" for newbies like me, Roberta. Appreciate it!

R1200rme
Posts: 5
Joined: Mon Oct 13, 2014 1:54 am

Re: prop shaft engine flange

Post by R1200rme » Tue Oct 30, 2018 2:19 am

Maybe use a "cup point" set screw? These, typically, do not require a spotting hole.

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