Promax cavitation on breakover with SHO

[Bullet 20cc]

I was washing the boat today and just for kicks I measured the Propshaft to pad and setback to compare to what I see other guys posting on here.

With the 10" Bobs Action Jacker I have 26" of setback from the end of the pad to the bottom rear corner of the jackplate. With the jackplate on 3 which seems to be best for top speed I measure the propshaft at 1" below the V-pad. The cavitation plate is 7.5" above the pad at that height.

No wonder this boat is tricky to set up.

That's a pretty high setting for your style of boat...even considering that setback. Some bass boats don't even run that high. Running that high will pretty much do exactly what you are experiencing...excellent top speeds at the expense of some slippage coming out of the hole (breakover). I would suggest lowering your jack plate a 1/4" (if possible) at a time until the breakover slippage goes away and you are also happy with top speed/handling until you find the "sweet" spot between both...while running the current Promax prop.

[Marshfly]

That's a pretty high setting for your style of boat...even considering that setback. Some bass boats don't even run that high. Running that high will pretty much do exactly what you are experiencing...excellent top speeds at the expense of some slippage coming out of the hole (breakover). I would suggest lowering your jack plate a 1/4" (if possible) at a time until the breakover slippage goes away and you are also happy with top speed/handling until you find the "sweet" spot between both...while running the current Promax prop.

My boat has a ventilated step, so it's designed for high engine heights. I run it at about 1.5" on the jackplate running around normally and on takeoff. The slip I'm getting on takeoff is at that setting. Trust me, my hydraulic jackplate is constantly being moved around while fishing so I've tried taking off all the way down which would put me around 4" below the pad.

I didn't get to run the 25" OT4 because the press in hub wasn't in straight but I'm wondering if that prop will give me the speed and economy I'm looking for and if adding a CBailey foil will give me back my holeshot.

I wouldn't even be screwing with all of this if the Promax didn't have so much better economy at midrange than the 23" OT4. Hard to give that up once you've seen it with a prop that will turn redline. It's a full 3/4-1mpg better from 3500-5000 rpm.

I'm beginning to think that my heavy boat starts acting like a considerably lighter boat once it gets on plane and the step gets the hull ventilated. That's why the Promax (which is designed for light boats) works so well up top but slips on the take off. Maybe have some PVS holes put in the 25" OT4.

[Triton19x2]

I have a mint condition 25.5 Bravo1 FS I may be willing to part with. I run all 8 PVS holes plugged. Some say that if the SHO does not recognize the resistance or load with the open PVS holes then the variable timing won't let it reach its full potential.

[Marshfly]

I have a mint condition 25.5 Bravo1 FS I may be willing to part with. I run all 8 PVS holes plugged. Some say that if the SHO does not recognize the resistance or load with the open PVS holes then the variable timing won't let it reach its full potential.

What speed are you getting with the 25.5 at what RPM? I've been looking for a 26 and passed up a couple of 25.5's because they are essentially heavily cupped 24's.

On a related note, I ran the 25 OT4 today. It'll be for sale as soon as I pull it off the boat. I'll use the money to order a CBailey foil.

[Triton19x2]

What speed are you getting with the 25.5 at what RPM? I've been looking for a 26 and passed up a couple of 25.5's because they are essentially heavily cupped 24's.

On a related note, I ran the 25 OT4 today. It'll be for sale as soon as I pull it off the boat. I'll use the money to order a CBailey foil.

67mph@5700 RPMs if I remember correctly