Need a faster prop

Tom Russo

Tom Russo

Active member
Hello all,

I have the slowest 14' South Bay duckboat on the LI's south shore. I have a 1998 Mariner 2-cycle 15hp outboard. The prop on it is not the factory prop. I don't know the size and pitch offhand but it is a 4-blade, larger diameter and flatter pitch than factory. As I understand, this prop should be better to push 2-men, dog, a couple dozen cork decoys, and gear. With just me, my son, and a doz. birds I'm just plugging along.

Can anyone recommend a faster/better prop for my setup or what the factory size/pitch is?

Thanks,

Tom
 
Hello all,

I have the slowest 14' South Bay duckboat on the LI's south shore. I have a 1998 Mariner 2-cycle 15hp outboard. The prop on it is not the factory prop. I don't know the size and pitch offhand but it is a 4-blade, larger diameter and flatter pitch than factory. As I understand, this prop should be better to push 2-men, dog, a couple dozen cork decoys, and gear. With just me, my son, and a doz. birds I'm just plugging along.

Can anyone recommend a faster/better prop for my setup or what the factory size/pitch is?

Thanks,

Tom
Click to expand...


Key information is the diameter and pitch of the prop and the RPMs you are getting under the loads you intend to carry, without those numbers is a guess.
 
I'm pitched down as far as I can go on a 25 merc. 11 pitch. Usually factory prop is 13' I;m putting on a dolphin wing on the cavitation plate. That might help. The lower the pitch the more power you will get.

Phil
 
Can't really run a dolefin on a southbay with the design of the transom. You probably just need the correct prop as a 15 will run a southbay fine with one adult and a kid, even with a dog. Once you start running with two adults and a dog or just more gear you're going to want a 25.
 
You need to get the pitch and diameter from the side of the prop. The 4 blader is a "power prop" made to get larger loads on plane. The factory prop should work fine. Check with local dealers, most have used props that you can try and are cheaper than new. You'll find the diameters are probably the same. With the boat fully loaded, keep going up in pitch, until you find one tha struggles getting on plane. Once there, step back down to the next lower pitch. If you feel like it's turning a lot of RPM at full throttle, have the prop sent out to be cupped. They'll bend the trailing edge of the blades, so it'll grab more water at speed. It won't effect its ability to get on plane.
 
Without taching it out it's just guess work.
I haven't used one but a lot of people recommend a "Tiny Tach", you just wrap a "antennae around a plug wire and it tells you the rpm's.
You want the engine in the high end of recommended rpm's while at full throttle and the boat in it's normal condition weight wise.
 
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