1974 Chrysler 75HP prop questions!!

[fcross69]

Hello all I was wanting to know about what other types of props I can run on this motor it has a 18 spline shaft running a shear key, with a prop nut and cotter key. I was told I can also run a non-splined prop on this with a shear key. Is this true. The older gentleman who told said running a non splined prop will just shear a key and less of a chance of hurting my lower unit is this true.

 

[Frank Acampora]

Re: 1974 Chrysler 75HP prop questions!!

There is a reason that all the big engines use splined propshafts. Yeah, you may be able to "get away" with using a non-splined prop and just the "shear pin" but then again, you may not.

However, The "shear pin" Is NOT a shear pin but a thrust pin. It is designed to take only the thrust load of the engine, not torque loads put on the prop.

You are limited to using 18 spline thrust pin props. They are obsolete and you can not buy a new one. However, they do come up for auction frequently on ebay. Just search Chrysler propellers. Some are auctioned at a reasonable price and some are expensive "Buy it now" listed by dealers. Some are NOS new old stock.

P.S. The "older gentleman" probably told Ole Evinrude how to mount his propellers. He has probably been around since Christ was a cub scout and is going to "sea isle"

 

[fcross69]

Re: 1974 Chrysler 75HP prop questions!!

I found a 18 splined prop today with a thrust pin, prop nut, and cotter key for 60 bucks was wondering if I tighten the prop nut until the prop stops on the thrust pin then tighten to cotter key?

 

[Frank Acampora]

Re: 1974 Chrysler 75HP prop questions!!

You put a correctly sized O-Ring over the propshaft threads and screw down the tailcone until one set of holes matches the hole in the shaft threads. Then insert a cotter pin. The tailcone usually does not seat all the way when a set of holes lines up and the O-Ring keeps it snug without you needing to overtighten it.

The O-ring should be about 9/16 inside diameter by 3/32 wall thickness. Don't think about it: A garden hose washer is too thick.