[bill harris]

Have factory prop should i going down or up on pitch

[rickdb1boat]

Less pitch would be appropriate. Not sure what size you need. You might want to contact a Prop Shop for more info on where to start for that size boat.

[OBJ]

Hi 1bill....Hey rickd....think maybe a four blade prop might also be appropriate. Sounds like he's pushin' a lot with the 40hp.OBJim

[bill harris]

sorry didn't talk about lake restrictions at 40hp :o

[steelespike]

Very important, be sure your motor runs in the proper rpm range when you settle on a prop.

[Forktail]

5,000 lb non-planing boat with 40 hp? Yikes. You'll want the smallest pitch and biggest diameter prop. This will give you the best thrust and highest rpm (you'll need it). Yamaha makes a 12 1/4 diam X 9 pitch for the 40. Trade the stock one in for that.2 or 4-stroke?FYI the 2-stroke 40 runs out at a max 5500 rpm with a 1.85 gear ratio. The 4-stroke runs at 6000 rpm with a 2.0 ratio.This means (without doing the calculations for you) that both the 2-stroke and the 4-stroke 40 produce about the exact same torque (WOT at prop) of 70 ftlbs. The 4-stroke's prop turns at a slightly higher rpm, so it would be slightly faster prop for prop, but hardly noticable. Since the 4-stroke's engine turns not only faster, but more often per revolution of the prop, it would probably have a better power and torque curve throughout the power band, especially under load. Ironically Yamaha's 4-stroke 40 is nearly identical in weight to the 2-stroke, so no performance lost with additional weight.