Prop advice/suggestions please

[Paul E]

Back to the quest for 50knots from a 19ft Boston Whaler with a 200 Opti...

Following on from my engine height thread recently, we haven't yet raised it, as it was said that a higher engine will level the boat out, and we need lots of trim to get from 42 at 'normal' trim up to 46-47 as it is.

It's running a 21" LaserII and revving to around 5,300rpm when trimmed right out (so much so that the engine note changes and there's a little rooster tail as the prop is starting to break the surface)

What kind (and size) of prop would you guys recommend to give us more natural bow lift and slightly higher rpm? It's a heavy hull but there must be 50knot+ performance there!

[Paul E]

someone must have a suggestion?

[larby]

A chopper or similar. I'm not sure of what kinda lift the 'off the shelf' merc props offer, but I believe they're all relatively neutral.

Again as far as I know, a chopper or yam drag would give bow lift, I'm sure we could find one around 21" pitch. I've got a 23 or 24 pitch one somewhere you're welcome to try though I'd imagine it'd be too tall. The only issue I can see is that they are over hub exhaust, so I don't know if this may give any holeshot issues, it must be a pretty heavy boat so the prop may just act as an egg whisk!

Being able to run with less positive trim will no doubt make a fair difference to top end, obviously ideal is to have the propshaft horizontal.

Thats my 2p, now I'll go see if I can find my chopper

James

[Paul E]

Are choppers ok for submerged use? I'd always assumed they were more for surface piercing applications? She is pretty heavy but there's no harm in trying, cheers mate

[larby]

I'm honestly not sure, though from what I know of how bow/stern lift comes about from a prop, being submerged would most likely affect a cleaver more. That said, my revenger ran a cleaver submerged, though I later found a bravo better.

Anyhoo, as you say, the only way to find out is to try! I can get to the shelves in the garage now, so shouldn't have an issue getting the prop out if you wanna give it a shot and see what happens. I've also got loads of cleavers, a bravo or 2 and a hydromotive 4 blade thru-hub cleaver if any of that helps, though most are at least 23 pitch, I don't do slow stuff!!

James