ok guys i built a small lt with 6.5 i just took my old gen motor (16 hp) off and put new one on and i was going to put this motor on my frame. what prop should i run ? ive heard 9x3, 9x7 ? not sure im new to this stuff.
its going on a 1570 boat.

Need help!

1570! Thats an airboat hull.

Did you measure it at the beam or bottom?
9x3

1570? better build another lt!

Well, at one point I discussed at lenght prop size for my 16 briggs LT with go devil. They insisted on a 9 x 3. But I had a 9 x 6 I had bought for 60$ from a coon ass selling some tools at a swap meet.

Go devil insisted this prop had too much pitch and would not be effective on my 16 briggs LT. Well I had it on hand so guess what......I put it on anyway!

The result? Go devil was right...and...go devil was wrong! You see a go devil is desighned to run in instances like thick goo and muck. And when in the goo they were right, it bogged my 16 briggs down and subsequently did not perform as effective.

But.......my boat took just slightly longer to plane out in clear water, but it DID still plane out and once it did it was a little faster! Yes my top rpm's dropped, I dont know to what, I dont run a tach! But the boat ran faster....it was obvious!

Bogged down a little more when idling along, took a little longer to get out the hole and plane out, worked a little harder to get on plane, didnt plow through the tough goo nearly as well, but gained some speed on the top end in the water.

And all this was on a 1442 riveted flat!

Dont let anybody tell you wont work! Think about what results you want and decide for yourself.

i would not go with anything with more pitch than the 9x3, custom propeller in alexandria la, usually will set you up with a 8.75 inch instead of the 9 to give you more rpms

i currently have a 16 hp longtail with a 9 x 6 and a 9 x 5 prop and they are both dogs on it
with 1 person it will run 16 mph, 2 people 12 to 13, 3 people 8, 4 people 5 mph
and the least little mud or grass loads then engine up severely, i am looking to re prop or sell complete unit and go with more hp