Need help choosing a new prop

B

BrotherWorm

Cadet
Joined
Aug 29, 2011
Messages
6
I have a 1979 100hp Johnson. The prop thats on it is a worn out aluminum prop that came on the motor when purchased brandnew. There's not any cup left in it. My problem is figuring out what pitch this prop is. Its not stamped anywhere. While I'm changing the prop I would like to go with something that might give me alittle more speed. Stainless is a must also. The motor is on a 16' Astroglass. Trimmed out it runs right at 40mph. I would really appreciate any advice given.
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Need help choosing a new prop

Please read the stickys at the top of the page and get us as much info as possible.
A prop shop may have to measure the prop for you.
A tach would be a big help to get your motor in the correct rpm range.
Also a guess of your boats weight would help.
Is the speed by gps?
 
B

BrotherWorm

Cadet
Joined
Aug 29, 2011
Messages
6
Re: Need help choosing a new prop

I'll do that. The speed is by speedometer. I'll get the other info and post it. Thanks alot for giving the time to get me started.
 
jimmbo

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,961
Re: Need help choosing a new prop

If your speedo is accurate, 40 mph on a 16 ft boat with a crank rated 100hp is pretty good. Most likely a 17 inch. Adding 2 inches pitch in theory will make the boat faster, but only if the engine, being more heavily loaded doesn't lose enough rpm to place you right back the same speed as before only with slower hole shot. BTW, cup on a prop does not wear out, it either has it or it doesn't. In the 70s OMC made props with and without cupping. If you go with a SS, raising the engine height, higher trim angles, are what will speed up the boat,
 
You must log in or register to reply here.
Top