What is the best prop for SPEED!

[Jaysad]

I have a 1990 21' Chris Craft OMC Crobra 5.0 HO.
I have a SS 4 3/4 x 19.
Is this the best for top speed?
41 MPH @ 4450 RPM, WOT me, the wife, and 2 kids, smooth water.
Does this sound right, or can I get more?

 

[NHGuy]

Re: What is the best prop for SPEED!

That sounds perfect. Wide Open Throttle should be 4200 to 4600 RPM. Do you know how to operate your power trim? Basically you start with the drive all the way down and once you get the boat on plane you raise the trim a bit to lift the boat's bow. This decreases wetted surface and improves speed. If you didn't know about that you might see a couple of more mph. Just trim it up gradually, if you ventilate your prop it loses grip and can over speed the engine which can cause big repairs.
ps. I bet you meant 14 3/4 X 19" prop.

 

[Jaysad]

Re: What is the best prop for SPEED!

Yes, I have replaced the trim sending unit on the drive, and the guage is working.
With the it trim all the way down, it reads 0. As i'm getting on plane I'll start triming it up to about 2 1/2 - 3 1/2... Just before the yellow starts.
Does that sound right?
It also has a black plasic fin/wing bolted across the lower unit.?? hydro foil??

 

[NHGuy]

Re: What is the best prop for SPEED!

Get the foil off, it aids low speed planing, especially with a heavy load, but it reduces top speed. Without the foil you will go faster. Also, don't get fixed on a certain drive angle for speed, experiment with it so you know how it acts at different speeds, with different loads, in different sea conditions and different wind conditions.
You might also be smart to search around for the best fuel. I often carry in jerry jugs with gas, but in the two summers I've had this boat I've filled up with Valvetect gas and seen real top end improvement. Both are same octane too, 89.

 

[Jaysad]

Re: What is the best prop for SPEED!

Ok thanks,
I'll get the foil off and play around the trim so more!
I have been running 89 this year, and it runs much, much better!
This winter I'm putting a four bbl. carb. intake, and 351 heads on
Any good idles on this?