Can I get some opinions on this prop?

[freightguy]

I am running a 19P right now and I am not happy with the production I am getting. At 5500 RPMs I am running about 45 MPH, which I dont feel is right. My boat is topping out at 55 MPH, but to get there the tach running off the gauge over 7000 RPMs. So I know there may be a tach issue as well, but still I dont feel the speed is where it should be.

http://miami.craigslist.org/brw/bpo/5862889674.html

This is a 26P. Is that too much of a jump?

 

[jumbofordman]

26 may be a bit much, but 19 is way too little. Probably want something in the 23-25 range.

 

[jumbofordman]

Oh, and your tach is reading correctly.

 

[freightguy]

Oh, and your tach is reading correctly.

Why do you say that? What I am finding online is telling me 5500 should be the max RPM.

 

[MateFever]

Black max engines don't have rev limiters so you are actually spinning the engine to 7000 rpm, nothing wrong with the tach at all. 5500 is the designed rpm pilot for that engine however you can safely run it up to 6000. Any more than that you are playing with fire.

 

[freightguy]

So what prop/pitch do you guys think was stock on this boat and why?

 

[jumbofordman]

I have no idea what was stock. I've run a same prop (unmarked except with a 25 dremeled into the side, so I'm guessing 25 pitch) on both a 150 and 175 on my Enchanter and the 150 pushes is to about 58, and the 175 to 62, both well under 6k rpms. With a known 23 it goes a little bit slower.

When I first bought my Predictor with a 150 Merc it had a 21 pitch prop and would go way over 6000 rpms, that's how I know 7k with a 19 is correct.

 

[70 ragtop]

One other thing to keep in mind, the even numbered Lasers are for the small lower unit, the odd numbers are for the Alphas and larger V6 lower.