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Hoping to get expertise on propeller selection for my new-to-me 1997 Dauntless 13. I've been reading your posts in response to other Dauntless owners but do not see anyone with my exact boat/motor combination. I have the original Mercury 40hp, 4-cyl, 2-stroke. Just had both carbs redone and runs smooth. From the prior owner, the motor has a very tired looking Mercury Spitfire 4-blade 8M8026625 which appears to be 10.6 x 12. I find this propeller to be quite unresponsive when performing close quarters maneuvering, it needs quite a bit of RPM to keep on plane and generally sluggish only seeing about 23mph on the GPS wide open with two passengers, trimmed as far out as possible prior to proposing and no excess gear onboard. Previous owner also installed a SE Sport 200 Hydrofoil. Motor is mounted all the way down - I looked at raising but it seemed the black trim on the top of the transom would interfere with the outboard bracket so I left it for now. Thank you in advance! -Trey

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Trey -

Discard the hydrofoil. That is a bandaid covering the problem of the engine being too low.

Move your engine up 2 holes to start. Trim the black piece of trim if necessary.

As for props - It is typical when changing from a 3 blade to a 4 blade to drop 2 inches of pitch.

I show owners with the Mercury classic 40hp and a 13/15' hull to recommend either a Mercury Black Max in 15" of pitch or a Yamaha painted stainless in 14" of pitch.

I would remove the foil, raise the engine, test the boat.

Then change the prop.

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Hi Phil, thank you for the advice. I've attached a photo of the outboard bracket and transom trim. If I wanted to avoid cutting the original transom trim, could I use the outboard bracket as a template and make a small offset/wedge for the outboard using 1/4" Starboard (or similar)? Then it would clear the black transom trim when raising the motor.

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Trying again with uploading that photo:

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To avoid cutting the trim you could make a spacer out of plastic (pvc, nylon etc) that is rectangular so the compression force is spread out. Think of it as a rectangular washer, rather than a circle.

You want it to be the same thickness, rather than a wedge.

Because the engine lower bolt position is not in a slot, your going to need to remove the engine from the transom to raise it. Given this, I would cut the trim under the engine bracket if in this situation using a hacksaw blade and utility knife. If there is a green line on the top of the fiberglass, I would coat it with a layer of Boat Life marine sealant.

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No question the engine is too low. That would make the foil run under water and thus be problematic.

If the engine is raised to the optimum level, you will see a great improvement. If that allows the AV plate to run flat on the surface of the water at plane, adding the foil will then further improve your performance.

My Whaler runs in the 3rd hole up and my DoelFin is the cats meow.

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Thank you all for the input. I raised the motor up two holes last night and plan to test over the weekend. I'll report back so we can figure out where to go next with propeller selection, etc. Here's what it looks like at the new height:

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And another angle:

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I finally got the boat back in the water and was able to retest with the motor mounted two holes higher. Right away I found the boat tracking much better at slow speed. Once on a plane I was able to use a much greater range of engine trim and did experienced little to no porpoising. Saw a little over 26 mph on the GPS. Overall, behaving like an entirely different boat! I could not be happier! Where do you all think I should go now with propeller selection?

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As listed in post # 2 above:

Mercury Black Max in 15" of pitch or a Yamaha painted stainless in 14" of pitch.

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Thank you, Tom. I’m online looking at these propellers right now and would benefit from a bit of additional guidance on diameter:

For the painted stainless steel Yamaha propeller, 14 pitch, I’ve found a 10.25” diameter with part number 663-45930-00-00, retailing around $450 give or take.

For the Mercury black max, 15 pitch, I've found a 10.125" diameter with part number 48-73140A45, retailing around $150 give or take.

Am I looking at the right options? For a $300 differential, will there be a noticeable difference (beyond the Stainless vs Aluminum) in handling/performance? Thank you!

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Given the chance it is not the right size, I would buy the aluminum.

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Thanks again Phil - I'll get the Black Max ordered and let you all know how it works out!

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I installed the Mercury black max, 15 pitch, 10.125" diameter (part number 48-73140A4).

Very noticeable improvement of maneuverability at the dock, the boat is now much more predictable and responsive vs the old 4 blade propeller.

With two people onboard, the boat would not get out of the hole unless I moved one passenger forward of the console and even that was slow. The old 4 blade 12 pitch would plane more easily, even with 4 people onboard. Once on plane, I did see nearly 28mph on the GPS. Had to keep 15-16mph to stay on plane. Cruised comfortably right around 20-21mph. Stable, no proposing but seemed more inclined to ventilate at higher trim.

The new propeller has solved my slow speed handling which is a big win but wondering if another option would allow me to plane more easily? By the way, I am still running the hydrofoil, would removing that assist with any of the conditions I mentioned? Thank you!

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While a 4 bladed prop allows a slower planing speed and increased acceleration, it reduces top speed.

With a 3 blade prop on a Dauntless hull, you may find the need to give it aggressive throttle to get up onto plane and then back the throttle down to prevent exceeding your intended cruise speed.

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Hi Phil, thank you. I'm going to wide open throttle to get on plane and the boat will not get up an go with two people on the RPS. It would before with the 4 blade. Do you think the 15 3 blade is too much pitch? Are there any other things I should be considering?

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I've removed the hydrofoil and went back out yesterday to re-test and get max RPM numbers. Boat performed largely the same without the hydrofoil, slightly more inclined to porpoise. Here is what I found:

-With three onboard, couldn't plane the boat even with throttle wide open and one passenger moving up to the very bow - I could get it to plane (but very slowly) with two all the way at the bow.
-With two people and throttle wide open, it will plane (again, very slowly) with one passenger moved to the very bow.

Ran wide open and trimmed out until the prop began to slip and then two taps back down on the trim. Reached 5200 RPM, max on this motor is 5500 RPM.

Your recommendations on where to go from here are greatly appreciated! I'd like to regain the ability to plane without a lot of load shifting and maintain the slow speed control at the dock that I'm getting now with this propeller. Thank you all in advance!

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What is the performance with the new Black Max prop AND the foil?

In reading some more reports, the foil does help even with the raised height for this specific model.

Note prop selection is very complicated. Need to factor boat hull, gear ratio, and the prop's blade design which is different for each prop model.

In the limited data I am seeing, it appears the Black Max 15" may not be the right prop for your boat.

I read one owner who has same model, different engine, went with a larger diameter, smaller pitch prop for better results.

If you had to pick between the 4 bladed and the new prop, which would you pick and why? What would be the biggest loss in the chosen prop?

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I put the foil back on and just ran the boat with the Mercury black max, 15 pitch, 10.125" diameter. Results identical to my post #14 (which was with the new prop and the foil).

With the foil and Black Max combo, the boat is more stable (little to no porpoising) at planing speed and tracks straighter at slow speeds. Great maneuverability at the dock, the boat is extremely responsive and predictable vs the old 4 blade propeller. With two people onboard, the boat would not get out of the hole at wide open throttle unless I moved one passenger forward of the console and even that was slow. The old 4 blade 12 pitch would plane more easily, even with 4 people onboard. Once on plane with the new prop, I did see nearly 28mph on the GPS at about 5200 RPM and a little over 29mph at 5350 RPM with one person onboard. Had to keep 15-16mph to stay on plane which is a little faster than with the 4 blade required. Cruised comfortably right around 20-21mph.

Bottom line regarding the foil & Black Max combo - it is better with the foil than without.

If I had to pick just between the new Mercury black max, 15 pitch, 10.125" diameter and the old 4 blade 12 pitch I'd keep the Black Max due to the better control/maneuverability around the dock. The biggest loss keeping the new prop is my lack ability to get the boat on plane (or get out of someones way if need be) with 2 or more people and I would like to regain that ability.

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I think you can find a prop that will give you the results you want AND be able to plane off.

Given the limited owner testing results of this engine and boat model, I would suggest you contact a real prop professional.

Ken Reeves of www.Propgods.com is well known and respected. He knows whalers. He offers trade in's while most other prop vendors do not.

I would share ALL the performance information you have and mention I recommended you contact him.

www.propgods.com

A second vendor is Dan's Discount Props. Don't let the name fool you. They are good.

https://dansdiscountprops.com/

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I spoke with Ken Reeves at PropGods.com and he reviewed my performance numbers. His recommendation is to stick with the Mercury Black Max / Quicksilver Black Diamond switch to the 10.375 x 13 pitch from my current 10.125 x 15 pitch. He feels that the 2" reduction in pitch will allow the motor to achieve plane more easily and the slightly larger diameter will keep the RPMs within range. Hoping to receive the propeller by this weekend and will report back on results once I've had it out to test. Thank you again!