Here's a question for ya.

If a certain single engine boat will run 80 with a Merc 525, how much faster should it go with a Merc 600?

What's the math on this one say?

About 1 MPH per $1,000

Ron
You know better than that, lots of variables.
If we are just guessing for fun I would say 84-86. 80mph is pretty fast already and its going to take some pretty big jumps in HP to push the hull faster.

Yep, I agree, lots of variables. But for fun I say you'd pick up about 4-5 mph

1 mph per 20hp, or 1 mph for every 200lbs

From what Ive been hearing the 525's are really pushing approx. 520-535hp. The 600's on a few 39 Nortechs and OL vs the 525's are seeing approx 2, maybe 3 mph. My guess in a single application would be 3mph, given all the variable were the same. Jeff

Good answers. I was guessing at 3mph as well.

That's an expensive three miles per hour.

It can be. I'm guessing this boat is in the 28' range? I would guess that you'd pick up a bit more than 3mph with a TRUE 75pshp increase. Unfortunately there is no general rule or formula. WAY too many variables.

Well a 525 makes 560 and a 600 makes 600 so you will pickup about 2 MPH

Ron,
We tried this link to a speed calculator.
We took the variables from 3 of our 30 foot Y2K Superboats with 3 different motors. The calculations worked for all of them.
First motor was a 496 mag, 375 HP. between 68-70 on GPS
Next was a 496 HO. We know Keiths boat Once Bitten does 74.2 MPH on GPS.
And Fast Eddie with a 525, best day, 83 mph, gps.

In the calculator I needed to figure out the constant, so I put in the hull weight, 4500 lbs, hp @ 420, and known speed of 74. It gave me a constant of 242.
I then ran the program with the different hp motors. Here is what it calculated.

496mag- 70 mph (right on the money)
496 HO - 74mph (right on the money)
525 - 83mph ( Fast Edddys best )
600 - 88mph from the calculation on the link

I guess we'll all get to see what it does one of these days

Rick