alum. or SS prop

[72 Hondo]

I need a little help here guy´s.
I have an ´82 mercury 115 w/ a 19p Alum. prop and runs 5300-5800 rpm @ about 45 to 50 mph. I want to pick up more speed and stay in the same rpm range. The boat is an 18´Crusder.
What do you guys think about SS w/ 19 or 21p? Blow out holes? Cupped? Over hub? Cleaver?........
Im confused!!!!!
GARY.

[Tom Brown]

I have an ´82 mercury 115 w/ a 19p Alum. prop and runs 5300-5800 rpm @ about 45 to 50 mph. I want to pick up more speed and stay in the same rpm range.
You're getting pretty good performance for an 115/L6 on an 18' boat. There's probably not more than a couple of mph to be had by changing props unless you go radical with a jack, high RPM, and so on.
You need a prop with a lot of bow lift. That's the only way you'll get your slip down and there's no other way to get more speed with the same RPM.
What do you guys think about SS w/ 19 or 21p?
No.
SS will knock you down a couple of hundred RPM. If you also add a couple of inches of pitch, you will lose another 4~500. That would be a great way to reduce your top speed and totally eliminate what little low end power you have now. The L6 is not an engine that likes to labor.
Blow out holes?
Yes
Over hub?
Yes
Cleaver?
No
You need less pitch, not more. If you're going to go SS, I'd look at something like an 17 or 18p Trophy. Don't hessitate to rev that engine to 6000 RPM, either. L6 engines eat pistons when over propped.
I think one of the best things you could do is drill some vent holes in the 19p aluminum prop you have now and just stick with that.

[72 Hondo]

Thanks for the info,
I will play with the cheap aluminum props to get an idea of what will happen before getting into stainless.
GARY.