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I have a 2017 Dauntless 240 with a 2017 300hp merc. I am currently running a 14.2 x 18 pitch stainless prop. I have only owned the boat for a few weeks. Purchased used. Questioning if this is the best prop option for me. Wondering if increasing the pitch might give me a faster cruising speed or better fuel economy or both.

Any Suggestions?

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Here is the link to the Boston Whaler performance report of the boat.

http://bostonwhaler.com.s3.amazonaws....a-2017.pdf

If you scroll down to the 3rd listing, 300hp, you will see the factory supplied prop, chosen by Boston Whaler for that boat/engine combination is a 14.25 x 18" Enertia prop.

Review the performance report and your actual performance. Create your own report and write down rpm, speed, gph, for each increment.

Note the factory test is only 53 gallons of fuel, no water and 20 lbs of gear (think anchor) and two people.

What is your actual performance? Are you using engine trim?

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Thanks for your response. First, I accidentally typed in 300 hp when my engine is actually 350hp. But when I access the report you suggested and compare my results with that for a 350hp, I'm extremely close.

Here's my deeper questions. I am currently running 27mph at 3500 rpms. How would my speed change at 3500 rpms if I bumped the pitch to 21 pitch? How would my speed change at 3500 rpms if I bumped the diameter of the prop to 16" but kept the pitch at 18? Trying to determine the change in results when I change diameters and pitches. Which is having the most effect.

Thanks

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In general, one does not change prop diameter to change performance - for a particular motor, you get a prop to fit it and that's that. You can change pitch, rake, and blade shape, with many offerings being available from different manufacturers. In general, Whaler will have selected a prop with good performance characteristics and making a change to improve one aspect of performance may adversely affect another.

What is it you are looking to accomplish by changing your prop? In any case,
before making any recommendations, we need to know the RPMs you are hitting at wide open throttle, with the motor and boat trimmed properly. You may also want to read up a bit on prop selection.

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Since basically Mercury, as Brunswick's majoj company, owns Boston Whaler, it is safe to assume both companies work together for the best overall performance of the boat. And nobody knows or manufactures props better than Mercury. So if they have decided, through their testing, the Enertia is the best prop for your rig, it probably is. Personally, I think the Enertia is the best prop you can buy for an all around boat like a Whaler running a 4-3/4" large gearcase outboard, regardless of the brand engine. Stay away from after market, alternative brand propellers for a Mercury outboard. NEVER are they as good as what Mercury offers.

I use Enertias on my Outrage 25 with twin 200 Mercs, and they are fantastic, and very fast, with excellent overall hull lift and great all around economy and performance. The Enertia is the successor to the widely used and highly regarded Mirage Plus, now a dated design from 30 years ago.

The only other prop I could recommend is the Revolution 4, which gives lots of stern lift and carrying capacity. But it may not be as fast top end as the Enertia.. You won''t know until you try one. It is for heavy boats with high HP like a 320 Outrage, and could be too much stern lift for a hull like yours. With it's aggressive 4 blade design, it will give strong mid range cruising at lower RPM. It's a big, heavy propeller. See Mercury's website for details.

As mentioned, props are NEVER bought by diameter. The prop manufacturer decides diameter based on the overall design and purpose of the prop. You select a prop based on the running characteristics you need, and the pitch, only. With a light load of only two people and half a tank of fuel, you select the pitch that will give your max rated RPM at full throttle.