Another prop question - looking for speed

[rocket350]

I have a 19' CC with a 3.0 Mercruiser Alpha 1 outdrive. I know it is a little engine. It has "3x14.8x19R" stamped on the prop. This boat gets out of the hole really good, but tops out at about 31 - 34 mph pushing about 4100 rpms. I am willing to sacrafice a little out of the hole for a bit more speed. I would be very satisfied if I could get 40mph.

Yes, timing, ignition and fuel systems are all good. I have toyed way too much with these. I have an awesome running engine as a result.

What prop pitch should I go with? Are props like a truck with a standard trans? Like changing props would be like taking off in 2nd gear vs 1st?

 

[Bondo]

Re: Another prop question - looking for speed

Another prop question - looking for speed

Ayuh,... So Why aren't you posting this Prop questionin the Prop forum,..??
This is the Motors, I/O forum....

but tops out at about 31 - 34 mph pushing about 4100 rpms.

You've already ran Out of horsepower,+ are lugging the motor...
It Ain't gonna go Any faster with a bigger prop...
Chances are,.. You'll Blow the motor from Detonation 1st.....

That motor likes to run at 4200/ 4600rpms at WOT....

 

[JustJason]

Re: Another prop question - looking for speed

this is a prop forum question but i'll throw in my 2.

a 3.0 in a 19 footer does not make for a fast boat...... period.

You are also to low in your rpms. You could have something wrong with the engine/hasn't been tuned up in a while or your just plain old overloading your boat.

With just you in the boat and a light load what are your rpms...
With you and the family and a high load what are your rpms....

Since your already a bit underpowered for that size boat you may want to carry 2 props depending on what your doing with the boat.

 

[TilliamWe]

Re: Another prop question - looking for speed

It's hard to believe you have good holeshot, but only turn 4100rpm at the top? You should have lousy holeshot.
Please confirm your tachometer and your speed (confirm the speed with GPS).

 

[hwsiii]

Re: Another prop question - looking for speed

Rocket, if you are only turning 4,100 RPM now with a 19" Pitch, if you change to a 21" Pitch prop you will be turning only 3,700 RPM and that Certainly going to lead to an early premature failure of your engine.


H

 

[kartman]

Re: Another prop question - looking for speed

im not a pro, but i would think that if you dropped to a 17pitch, you would get a better holeshot, and turn that motor where it wants to therefore picking up top speed as well. but i think that 40 is pushin it. prolly 36 tops. good luck!