1956 Johnson 15 hp RPM range?

I looked it up on the link to boatinfo? and reading on there is 4000 RPM? I assume thats where the 15 hp output will be. Can anyone confirm that? Also on that same site I was looking at the OP manual for the 18 hp and in the book it says they came with a 9 1/4 x 11 prop. Anyone have any info on what prop the 15 hp came out with in 56?

Thanks
Steve

I show 4000 as being the RPM specs also so that is where the 15hp should be at. The 18hp didn't come out until 1957 I believe and it was a different motor and displacement so its likely they didn't have same prop size. Maybe Pappy will see this post and chime in, he is good with these vintage beauty's

I know the 9 1/4x 11 prop wont work on my boat. Thats what is on there now and its too big. Just trying to get a idea what came from the factory. All of the props I find online are 9 inch.

Steve

To big as in diameter?

As in pitch. The 9 1/4 inch diameter works but its real close but the 11 pitch is too much. Too much load on the motor. It was on the motor when I bought it. I am wondering what size and pitch came on the 15 hp in 56 from the factory. I got to get a tach on it and see what its turning then go from there. I am guessing that the 15 hp came with a 9x9 or 9x10 from the factory. I got the part number for the prop but cant find any specs on that part.

Steve

Cabelas and BPS both list a 9" x 10" pin drive prop.

I found a brochure online and it came with a 9"x11" prop. But that extra 1/4" on diameter isnt going to load the motor up that much is it? I wouldnt think it would make that much difference. But I also found another problem. But got it fixed.

Steve

Without knowing the RPM the engine is turning we are just spinning our wheels aren't we?
Have had several '54-'56 15hp engine in both Johnson and Evinrude flavors. Still have a '54 Evinrude that will be going up for sale this weekend.
The production prop always seemed to work well.
That engine is very light and was a powerhouse for it's day. There are those who will claim it is as fast as the later 18hp engines although I haven't seen this.