Changing prop size.

[Gator Slayer]

I have a 25hp Yamaha 2 stroke on a 1546 MV jon boat. I can barely get it to plane when fully loaded (~1200 lbs total weight). I can buy a new prop and have the option of a 9 7/8 x 10 1/2 or 9 7/8 x 9. Currently it has a 9 7/8 x 11 1/4. Empty this thing screams at about 30mph on the GPS. Which prop would be the best for my fully loaded trips. Thanks for any advice.

[Fishing Junky]

The 9 7/8 x 9 prop would be your better fully loaded prop.

[Surface Tension]

I agree that that would be a better prop with a full load.

Empty load and the RPMs will be way up there so either change props with loads or keep the RPMs down when empty.

[Surface Tension]

I'll expand on this subject.

I and know FJ as well run 16'ers and 25 hp outboards on the motor routes with heavy loads. Distance of travel for me dictates that the prop selection is made for the heavy load however this particular boat is set up and used for only those trips. On another boat I rigged for this long heavy travel I had the prop cupped by Jay Soderbloom. That gave me the power I needed but still had that speed when empty without excessive RPMs.

Something else that makes a night and day difference is load distribution. The bow will raise no matter how much weight you have there. The stern however won't so besides yourself leave the stern empty or at least load that area with the light bulky stuff with the majority of the weight in the bow and mid section. Try it, it'll make the huge difference.

[Gator Slayer]

Hey ST thanks for the tips. Picked up a 9 7/8 by 9 inch prop. Works like a charm. I can now run faster and on plane than with the 11 1/4 prop. Could you expound on the cupping? I'm not sure I follow, it seams you are saying I could cup the 11 1/14 and get the same fully loaded performance as the 9 pitch? How's that work? Thanks for all the advice, I'm already much happier with the way the boat runs.

[Surface Tension]

You can't get the same performance but you can get some power from doing so and not slip in speed as much.

Sounds like the switch you made will be good for you on both speed and loads. I'd leave it there.