Prop for 23 SeaCraft with transom-mounted Merc 250 EFI

[wattaway2]

OK you got me to bite on this one . I have thought about the design of T tops for a while I having had mine custom-made it was always intrigued about how the angle of the top acted knowing full well that if it angled down it would be driving the boat into the water and too much at the front would act like a Parachute. The idea of designing it like a wing is intriguing! again the angle in relationship to a boat/deck that is constantly changing going up and down a wave is of concern and debate in my mind. I Would think that it would continue to supply lift to the hull And then again we would need to consider the placement as too far forward or too far aft could be the detrimental

[rdoaner123]

Well I raised the motor a hole and rpms increased to 5,600, but speed stayed around the same. Still running the mirage plus 17 pitch.

Seeing as it's frustrating the prop will ventilate when accelerating in a straight line (flat conditions), my priorities are primarily the prop that has the most bite. Also since I have no trim tabs, the prop with the most stern lift would be desirable.

Re-reading everyone's replies, seems like the REV4 is the ticket. Any objections?

Since I'm only seeing 5,600rpm with the Mirage Plus, does it make sense to go with a 15 pitch Rev4? I'm concerned about the rpm loss

[gofastsandman]

Originally Posted by wattaway2

OK you got me to bite on this one . I have thought about the design of T tops for a while I having had mine custom-made it was always intrigued about how the angle of the top acted knowing full well that if it angled down it would be driving the boat into the water and too much at the front would act like a Parachute. The idea of designing it like a wing is intriguing! again the angle in relationship to a boat/deck that is constantly changing going up and down a wave is of concern and debate in my mind. I Would think that it would continue to supply lift to the hull And then again we would need to consider the placement as too far forward or too far aft could be the detrimental

Lots to consider.

Carl designed and ran a flying wing hull.

I think the ocean being water and the air being easily compressed may
present too many variables to be done safely. It would be difficult
to fish around a tail section as well.

The sailing cup racers are using foils with wind and underwater.
Lots of carbon fiber and ridiculous forces.

[joshmon71]

I love my Rev4. Never went back to a mirage plus. same issue as you cavitated with M+ only on turns. 250 Verado had a17P R4, and was just barely getting WOT needed. When I sourced a 275 ECU it was perfect peachy with a 17P R4 so you are probably right its on the edge of a 17P or 15P R4. Turns out I could have gone much higher with the R4....never did raise from 2008- till this season with a one year old used 300 Verado i snagged.

No idea why or where read (tht? and propgod?), but the 15P Rev4 had some reason for not being advisable desirable.

Raise you engine even more and get a R4 17P....I suppose you could go silly $$ and get a R4 XP 17P....

Right now, 300 V8, R4, running a 19P R4 heavy load and barely if even need to trim up, hitting 6K which is max end of WOT range. DO have tabs. I had the marina raise the engine so high I was sure it would need to go back down. I was wrong. Those R4s can really run high. I am debating a 20P or even 21P R4 for this summer.

GL, def some art and voodo to propping, heights.

[rdoaner123]

As an update, I tried the REV4 17 pitch and lost 6mph and 500rpm. It certainly held a lot better, but the loss in performance is too much. I'm thinking of trying Bigshrimpin's suggestion and going with an Enertia. I see he recommends an 18 pitch; does the enertia turn more rpm than the Mirage plus? I wouldn't mind gaining a few rpm bringing it up to 5,800 with a light load if that's the case