TOPIC: 1966 Johnson 100 Hp Prop Question

When I got my motor, both props were badly beaten up. One looks beyond repair and the other is showing lots of metal fatigue.

In any event, I have bought two props off of craigslist that are the recommended part numbers. A 381020 and a381021.

The prop that is on there now, which doesn't have an OMC number covers the entire gearcase head. However, BOTH of the replacements have a reveal of about 1/4" around. I'm not sure if it makes a difference or if it is because the prop on the boat is a 14 1/4 by 14 while the ones I bought were 12 1/2 x 16 and 18. In doing more research, it appears the 2 props that came with it are from OMC i120 sterndrives of the same vintage. I found a Michigan Steel number on one of them and tracked it down.

So are the replacements I got okay with the reveal around the edge?

I've attached two pictures that hopefully you can see what I'm talking about.

Dave. I have the same setup with the two different props. As long as there is no "slop" or play, no binding you should be good to go. Put the shear pin in and spin the prop by hand. You might need a thin shim washer behind it. If you have to pull the prop forward to insert the pin you could use a shim.
When I put on the more aggressive prop (bottom picture) there was a big difference in hole shot and a slight increase in top end.

The 100 HP & the I/O were both built on the same gearcase structure. Prop is physically correct BUT the pitch will be way too much for you.

Thanks for the info. Ironically enough the 14 1/4 x 14 looks good on the engine, It fits the gear case lines really well. But, I did mount the 12 1/2 x 18. I also have a 12 1/2 x 16" which was the standard one provided with the motor.

The boat is very light st 500lbs plus the 275lbs of engine. After the sea trial, I can see which one seems to work better.

Sincerely,
David

Dave. Me thinks you're on the right track, try them all out and see what you like. Always good to have a spare prop tucked away along with the shear pins.
The boat I'm running with the 100hp is a very deep and wide 17 footer Shell Lake Executive with an added ton of Honduran mahogany on top. When "hole shot" and "top end" are said, take it with a little salt. Top end for the beast is about 32mph. Hole shot by my standards means it gets up on plane without any problems. Boat was rebuilt for comfort crusin'.

I've got a bronze one that's in excellent condition if anyone is interested.