The PVS Phenomena!

[WillySteve]

I've worked with props and prop venting for many years and in a lot of cases "some venting" will help a hole shot......HOWEVER:
in messing with my current set-up on my current boat I have come across something weird...(to me)!

Set-up is:
20' Bullet, pretty heavy loaded,
Merc 260,
15" set back,
Prop to pad 1.5 over,
ProMax prop with 4- factory PVS and 4- 1/2" holes machined just behind the original PVS.

What I've noticed in messin'wit this thing is when I close ALL the relief holes the boat launches straight forward, (without even breaking over), and on top running in 1-2 seconds....even with part throttle launches!
When I start opening holes I start getting more and more of a break over, (and way slower on plane times), with the bow raising extremely high, then the mota revving as per the amount of venting increases.

I guess what's happening is the venting is really hurting on plane times when your set up is above pad as you are losing your forward momentum as the prop vents and loses contact with water that's prolly already aerated from the boat hull....What Say Y'all?

Here is a short vid with only 2 of the 1/2" holes open:

https://www.youtube.com/watch?v=_y_OkJICU_Q

[gfinch]

Yep, I agree with you. If the engine has enough torque (doesn't bog) to continue to push the boat forward without slippage (loss of traction) and the trim can keep up the boat just launches onto plane. No bow rise and no flop and rise.
Very, very good work getting to this point! Impressive.

[WillySteve]

Yep, I agree with you. If the engine has enough torque (doesn't bog) to continue to push the boat forward without slippage (loss of traction) and the trim can keep up the boat just launches onto plane. No bow rise and no flop and rise.
Very, very good work getting to this point! Impressive.

Thanks Gary, don't know if you noticed but on the last couple of hs's I raised the trim up some and still launched with little to no bow rise!

[whipper]

I find with motor raised up is always best hole shot for me also with no pvs holes. Grab,lift and go. gota like that. With the prop shaft buried your starting from deep in the hole and have to far to come up from. Pluss when the prop starts spinning your digging that hole deeper! Like Gary Said if you have enough power to spin the prop size for your setup pvs holes on surface irritate unnecessarily before the pressure side of the prop crating slip. Of course the style of prop has alot to do with this equation. Sounds like you have a keeper though. Nice not to have to go threw 10 pluss props to find one that works for your setup!! BTW she cooks along quite nicely doesn't she!!

[gfinch]

Hey Whipper this picture is for you....since you should be still frozen. Yellow,Green zucchini squash. Tomatoes 2 kinds. Strawberry raised bed.

[whipper]

haha yes Gary it was minus 15 last night night!! Warmed up today to 38 first day in 4 month above 32f during the day!! lol about 4ft of snow in the yard still this pic was from last week still looks the same out.

[90 5.0]

Boat weight, prop pitch and motor set up obviously have lots to do with this.

What ive found is on heavier loads, and higher pitch props is where the venting helps, if the motor is trying to bog down.

You didn’t say, or if you did I missed it. What pitch is the prop? 25-26? On these pitches and lower on my Bullet pvs holes surge and slow the boat down as well, as it has enough hp to just blow them out, where without Them it hooks and is gone.

Another example, on my old tr-21 triton with 250xs and 1.68 years, with a 23 no added holes was the best, but with a 26 or 28 especially it absolutely had to have venting to get on plane with a full load and fish in the well.

With a 23 high five and just the little stock vents it would launch hard enough you could just about race it that way lol. With a 28 and no added holes partner had to sit in front deck just to get on plane with a limit in the well.

Nice holeshot by the way; especially with duel pp’s.

[WillySteve]

Boat weight, prop pitch and motor set up obviously have lots to do with this.

What ive found is on heavier loads, and higher pitch props is where the venting helps, if the motor is trying to bog down.

You didn’t say, or if you did I missed it. What pitch is the prop? 25-26? On these pitches and lower on my Bullet pvs holes surge and slow the boat down as well, as it has enough hp to just blow them out, where without Them it hooks and is gone.

Another example, on my old tr-21 triton with 250xs and 1.68 years, with a 23 no added holes was the best, but with a 26 or 28 especially it absolutely had to have venting to get on plane with a full load and fish in the well.

With a 23 high five and just the little stock vents it would launch hard enough you could just about race it that way lol. With a 28 and no added holes partner had to sit in front deck just to get on plane with a limit in the well.

Nice holeshot by the way; especially with duel pp’s.

Hey Robert....hope you are back in the saddle!!!!
Prop is a PM 24p. Yeah, I have to run 2 holes open on my PM 27 and then it's back to having bow rise and all that goes with it. Actually the boat runs as fast as I want to go with the 24 thanks to not having a rev limiter....plus the great launch so looks like it's found a home!