Prop suggestions wanted

[Mark]

Stan
Here's the skinny. You would need a 25" prop minimum to get to 74 MPH. Even if the prop is tweaked it is at best one pitch up or down. Secondly, your tach is probably correct (or close) since it is very unlikely that motor would turn 7000+ RPM. BTW which 150 is it ...2.0L, 2.4L or 2.5L? They all have different gear ratios...2:1, 1.78:1 and 1.87. But still that is not going to acount for 20 MPH.
A GPS can get a rogue reading once and a while. That is my best guess. Like I said I have been running these hulls for years and it is just not physically possible. If you had 1-2' of chop that boat will be bouncing all over the place. They are very light and get airborn in conditions like that. Loads of fun though.
You'll have to get out again in smoother water. You should be able to turn that prop to 5600-6000 once you are trimmed out (maybe a liitle less if it is only a 2.0L). On a good day you should hit 60 MPH. Nothing to sneeze at for that setup and really all they are build to handle. Have fun.

 

[Supernova]

O.K. Thanks Mark. I was reading somewhere else that a radar gun is the only truly accurate way to check speed. I'll try to get up there this weekend and run it again.

Yeah, in 1-2' chop it definitely was a hairy ride. But I am used to open Bay and offshore conditions, so it didn't phase me too much. Just for reference it was going fast enough that it felt like it wanted to blow over a couple of times. And the chine walk did start around 55 and was very difficult to deal with. Also the steering got really tight, as in hard to turn the wheel.

I also am going to check gear ratio on it tonight. I know in the Mercruiser outdrives it was not too hard to change ratio, but I don't know about these or if custom gearsets are even available, but a set of 1.5's would do just what I think it's doing, and it's got a brand new lower on it.

I also agree that if the pitch was changed, it would only be by 1" maybe.
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Stan