I would greatly appreciate some expertise

[DSQ]

2 days ago I purchased a 1996 15' Dauntless powered by a 2003 40 HP 4-stroke Merc with literally 30 hours on it. I test drove the boat before I got it with 3 people on board-then 2 and still had quite a lag getting out of the hole. I knew the boat was somewhat underpowered but I wanted a BW and after shopping for 2 mths I couldn't have gotten a better deal. The motor literally has 30 hours on it and repowering is not an option. After reading a lot of posts I have pretty much decided on Nauticus Smart tabs. Additionally I'd like to replace the prop. I believe the current prop is a Black Max 13" pitch, 10-3/8" diameter, 3-Blade aluminum prop My primary purpose for the boat is simply for getting from point A to B. After much research my head hurts and I still don't understand the pitch/prop science but I believe I'll have to sacrifice some top-end speed for hole torque. My question is which prop would be the best option?

Thank you for your feedback.

DQ

 

[steelespike]

Marine engines work very hard,like towing a trailer up a never ending hill. Higher pitches are like higher gears in a car.
They are harder to turn but if they do well could make good speed.Lower pitches produce more power but may lack high speed
and may over rev like the lower gears on a car.The 4 stroke needs to operate within its rated rpm range 5500 to 6000 usually shading to the higher rpm numbers.
Thus we need a lightly loaded wot(wide open throttle) test run just you the motor and boat.Need the rpm and gps speed.Have you tried trimming down as you add weight?
Is the antivent plate(just above the prop) about even with the bottom. Are the tank and battery stored near the transom?
Once we have your lightly loaded numbers we can suggest a prop.
With the understanding it may be a starting point.

 

[Sea Rider]

You have to ask yourself if you'll be boating with 3, say family oriented at all times or most times with a a 15 footer and a under powered OB. Weight affects wot rpm, more weight, less rpm, less weight more rpm. Try to dial a prop for OB to rev at max wot rpm range for that 40 HP, once there can throttle at the speed you like most. Will need to install a tach, induction tach, if without one, you're dead blindly guessing.

Before investing on trim tabs, buy a tach, dial a top performer prop to run max wot revs with 3 up and lastly add trim tabs if needed. The speed difference between top hole shot and top end speed is just 1-2 MPH at the most. Much better is superb hole shot with weight than max top speed when going from A to B.

Happy Boating

 

[DSQ]

It does have a tach. I am detailing it and taking care of a few issues-will have it in the water in 10 days or so. I will pay attention to the RPMs and speed and then re-post. Thank you very much for the feedback.