OMC Propeller sizes

[rick001]

I have a 1984 OMC stringer drive on a 5.7 L. My question is about propeller size. When I bought this boat it had a stainless steel propeller marked 14 1/4 X 19. My mechanic told me to put the stock propeller back on it, and it is marked 15 X 17. I know the last number is pitch, but isn't the first number splines? And if so, how does a 14 1/4 spline fit on a 15 spline?

 

[Bondo]

Re: OMC Propeller sizes

I have a 1984 OMC stringer drive on a 5.7 L. My question is about propeller size. When I bought this boat it had a stainless steel propeller marked 14 1/4 X 19. My mechanic told me to put the stock propeller back on it, and it is marked 15 X 17. I know the last number is pitch, but isn't the first number splines? And if so, how does a 14 1/4 spline fit on a 15 spline?

Naw,... it's Diameter,...

 

[bimmi]

Re: OMC Propeller sizes

How big a boat we talking about most say 3000 lbs boat 5.7 should easly pull a19 wheel and even 21 3 blade if it;s 4 blade go down one size

 

[rick001]

Re: OMC Propeller sizes

I put the stock prop back on. It's a 3 blade 15X17 aluminum. I got a little lower top end, but it gets on plane a lot faster. My top end went from 50 to 43 at 4200 RPMs. I'm okay with that as that is plenty fast. My boat is a 19' Marlin with a cuddy cabin, not sure of the weight but I'd have to guess it's about 2000 lbs.

 

[limitout]

Re: OMC Propeller sizes

the 14 1/4 diameter is probably what your mechanic knew was wrong for it but the pitch might you had might be correct so try a 15x19 and see how it does.

I haven't seen anything about rpms and THATS what matters not the speed you get out of it, so what are your rpms running and what is the range you are supposed to be within?

 

[rick001]

Re: OMC Propeller sizes

My mechanic told me it should run at 4000 to 4200 RPM. And it does.

 

[jestor68]

Re: OMC Propeller sizes

Now that we have the diameter/pitch thing down; we should establish the WOT rpm range as 4200-4600 rpm for the 1984 OMC 5.7L.

 

[rick001]

Re: OMC Propeller sizes

As I said, its running at 4200 RPM WOT. With the stock prop I'm getting about 43mph (gps). Which is fast enough for me. I seldom go to wot for very long.
I live in Arizona, so I get to go boating year round. Last weekend I changed props in the water and it was a little chilly. The air temp was 85, but the water was 65.