For the prop guru's

I have a 9.25 x 8 pitch now, was a huge difference over the 9 pitch. I added 500lbs of weight to the boat, Im guessing my loaded hull weight is in the neighborhood of 1500-1700 lbs, I was debating trying a 10x7. any suggestions etc? I did jack the motor 3" I have no slippage now, I am just plowing to much water. 96 johnson 15hp.

That's alot of weight for a 15hp to push. Chances are if you go to a 7" you will just increase the motors wot rpm's with no gain in speed. If you can get that rig up to 10mph I'd call it good. Do you know your rpm's or speed?

Not looking for plane, it ran 12.9 500 lbs ago, it runs about 9 now. I did loose some rpm, i was thinking the 7 would handle the added weight a bit better.

Took a look at what you are pushing. The 10" diameter on the 7" pitch prop will be just what you are looking for. Larger blade area is what you need.
General rule of thumb here is that if you want to go fast you propel a small column of water at a high speed and if you want to push a heavy load you propel a large column of water at a low speed. Think tug boat prop vs. a performance bass boat prop.
Also, you do not want to lug a two stroke! Go for it.

Thanks Pappy, 3 or 4 blade, would stainless benefit me any?

Remember, when you need to push a heavy load you need blade area to move as much water as you can. I haven't looked at what's available for that engine in the low pitch you need but if you can get a 7" pitch prop in a four blade go for it.

I picked up a 10 x 7 3 blade factory new prop today, i may get a 4 blade later and try it

I'm not a guru but without a tach you are shooting in the dark. I'm running a 25 year old 15HP 2-stroke currently and just fitted my tach last week. I have 2 props for the motor, the 9.8P and the 8.4P listed in my owners manual. I can only get the 9.8P up to 4000 rpms. I have yet to get a reading on my 8.4P but will post as soon as I do. For my own comparison, I traced the outline of my blades. To make matters even worse, the 9.8P would not get on plane at all at a 7700 foot altitude, last month, even after a carb adjust. :?

I could use a tach, but you can always tell when a 2 stroke is running clean, i know i need more rpms to do that, i can just tell.

The 10x7 put my rpms really in the sweet spot I think, I did manage a bit more lift in the stern as well I think, now I just need a 60" tiller extension and Ill be good I think, when I get time Im gonna raise the motor 1 more inch I think, and try it out.

Happy it worked out for you.
To answer your PM on HP increase the best thing you can do is to raise the intake ports slightly and square them as well as square the exhaust ports. Cut the cylinder head around .030 as well. Keep the RPMs high as you will lose bottom end torque.
Much easier than trying to enlarge the carburetor and going through the nightmare of the change of intake signal at low to midrange RPMS. If that required anything other than standard jetting you would be buying another carb and back to square one. That change is one you make on an engine designed to start up and be run at or near WOT all the time. Something like an Alky engine.

Interesting.

Pappy, if the head is shaved .030 do you have to do anything with the squish gap?

The squish band will be reduced. May need to go to a little cooler plug as well. Read the spark plug and determine that. Havent done a 15. Any of my engines were either 3 cylinders, V6, or V8 outboards that I changed. That is what I would do first if I wanted to go that route. for your boat I would leave it alone and go to a larger engine. This stuff is mainly for lighter faster boats. Hot engines pushing heavy boats normally have a shorter life!