CONTINUOUSWAVE

Give me performance information for a 150 MONTAUK that weighs 950-lbs with a Yamaha F70.

Q1: what propeller will be best for a 150 MONTAUK with a Yamaha F70?

Q2: how does the performance of a 150 MONTAUK with a Yamaha F70 compare to the performance with the original Mercury 60-HP BIGFOOT engine?

The first generation 150 MONTAUK (up to 2016) has the same weight as the Montauk 17 at 950-lbs. For this reason I would suggest the following propellers for the F70 to start:

• 13 x 17 Yamaha Painted SS
• 13.25 x 14 Yamaha Performance Series
• 13-1/4 x 17 Turbo 1
• 13.25 x 14 PowerTech SCP

As for performance, the factory shows boat speed at WOT as 36-MPH with the standard Mercury 60-HP. With an F70, I calculate you should be able to reach 40 to 41-MPH.

The post-2016 150 MONTAUK weighs 200-lbs more (1,150-lbs), so I would drop two inches of pitch.

I don't have any first-hand experience from which to offer advice, but I do have two observations:

Phil T wrote:... I would suggest the following propellers for the F70 to start.

• 13 x 17 Yamaha Painted SS
• 13.25 x 14 Yamaha Performance Series
• 13-1/4 x 17 Turbo 1
• 13.25 x 14 PowerTech SCP

There is range of pitch in those four suggested propellers of three inches, from 14 pitch to 17 pitch. I suspect that some of the propellers may be three-bladed and others are four-bladed. That might account for the unusually wide range of pitches suggested.

Phil T wrote:...the factory shows boat speed at WOT as 36-MPH with the standard Mercury 60-HP. With an F70, I calculate you should be able to reach 40 to 41-MPH.

Assuming there was no change in total weight, an increase to 70-HP from 60-HP would tend to increase the boat speed by a ratio of (70/60)^0.5 or 1.08. This implies a new boat speed of 1.08 x 36 or 39-MPH. Also, any increase in weight due to the more powerful engine will tend to reduce boat speed.

You can calculate the effect of changes in horsepower or weight on boat speed with the calculator I have created using the experiences of naval architect George Crouch, which I call Crouch's Calculator. See

Crouch's Calculator
https://continuouswave.com/calculators/crouchCalc.php

All of the propellers I listed are three-bladed. The blade design differences explain the disparity in the pitch size.