3 Blade prop to 4 blade prop

1” pitch isn’t going to get you any measurable speed and just going to overload the motors. You’re better off spinning them 25 rpms more with the props you have. You want speed, soda blast off the years and years of bottom paint you probably have. I picked up 2.5-3 knots on a yacht that was less than 10 years by doing that

All good advice. Bottom will be clean and repainted. There's no tower or dinghy. If 26x26 is what she probably came with then whatever I get will be fine by me

I surveyed a 46 last summer with 4 blade wheels 26x26. She had 6-71's and made 25 knots. So there's that

How many knots do you think I might pick up blasting the bottom paint off my 42 - there is anywhere between at least 10 and potentially up to 40 years worth

From what I've read those 92's are rated for 2300. They spun right up to 2350 where I backed off because my Detroit guy was along for the ride which leads me to believe I'm leaving something on the table here.

I gained 10% in speed. Think of all of the weight of a can of bottom paint, half of that weight stays on the bottom after it dries. Then the un-even bottom.

Thanks J. I've had two different yards vehemently talk me out of it. I usually get "Unless you can't sleep at night by occasionally dropping a bottom paint flake on the bottom of the bay you'd be (*&^ing crazy to go through all that just to gain a knot."

It's still on my list, however it's priority level has never been high enough to beat out other projects.

Got my original 3-blades tuned up by Johnson Machine in Freeport to 26x26 the original specs for the boat. Huge thanks to Rich M who gave me his old wheels as spares- 26x28. Now I have a "hot rod" set to try if the ones I have don't get the speed I'm after

My Diesel guy did a check of the shafts there is some run-out on the port but they are straight. Going to see how it is in the water. Will report back

Sorry just realized I never updated this thread. So the 26x28 3-blades went on and she flew right up to 26 knots in the spring... With 1/3 fuel and no water onboard. Loaded her up and lost about 300 rpm and made a little smoke. Took those wheels down to 27" pitch and she seems to have found the sweet spot. 2350 rpm and around 24 knots give or take. At 2000 rpm I'm making 20. Good enough for me.