Chopper blowout ?

[Toostrokin]

I am having a problem with terrible ventalation on my 19 Ft liberator picklefork.
I am currently running a 30 pitch big ear chopper and it cavatates bad while trying to get on plane. Over 10 mph it hooks hard and stays hooked until coming off plane.Is this normal for these props? I am running a 2.4 with bobs cone and cut exhaust .

[props4u2]

Sounds like you're talking about ventilation while taking off, not blowout, two different animals.
A good prop man that works on hi-perf props can help this dramaticly.
If you can't find anyone close by, call Robbie @ 804-706-1847.


Lee

[SportJ-US-1]

Yeap, on getting on plane slip is called ventilation. Blow out s a gearcase cased which happens at high speeds only. Try doing a gentle turn while trying to get on plane and don't rev over 3500 to 4000.

[pyro]

It's normal, but it's worst with tall-pitched choppers, particularly bad with the narrow-bladed A4/A5 30p model. Some extra cupping will help give it some "grip" when planing, but there may be some better prop choices out there also...

[Lockjaw]

My slow bassboat will barely plane with a chopper, and i have to have transom wedges in, and it still ventilates like crazy. I believe adding cup to the back side of the blade will help that, but check with a good prop guy.

In the last test of props in B&WB mag, they had problems with a chopper II on the boat they were testing. It took forever to plane.

[pyro]

Choppers slip while planing because the prop is spinning so fast it can't inhale enough water to produce any thrust. Each blade is slicing off a little water and slinging it backwards, but mostly just churning air. Once the boat's speed catches up with the blade rotation enough to feed the leading edges some clean water, the RPM's drop and it bites again. Excessive negative trim doesn't help much, because the thrust that normally forces the bow down just isn't there at the point that it's slipping, the prop is just working harder trying to push air bubbles straight down. Easing off the throttle while it'
s slipping lets it "catch up."

Extra trailing edge cupping, as well as some mild leading edge cup near the hub (sometimes called "roll") will allow the prop to produce more thrust with less water, this gives it more holeshot bite, and also more bow lift and tolerance of higher running height. It's a night-and-day difference. The prop will "pull" throught the rev zone instead of slipping through it.

Get your hands on a true 28p "BIG-ear" chopper and have it re-worked by a good shop, it will run like a 30 when it's done, and it will pull like a mother...

[vector mike]

Choppers suck when trying to plane. That is one reason I don't use them. Tried both big and small ear and both are the same. My Cleavers work great out of the hole and on top end. More cup on the Choppers should grab better but why mess with them if the Cleaver works all around better.

[brotherxb03]

Depends what boat your on and how it's set up.My xb03 Allison jumps out the hole with a 28 stock chopper.

[150aintenuff]

if your RPM is climing over about 4600-5000 your churnin air... time to do some prop work to work on hole shot... feathering the throttle helps a bit but the cure is to tweek the existing or find a different prop.

[Steven]

i never liked choppers for that reason and some of the big ears seem to stick the nose up and plant the stern down for a boring ride. HOWEVER....:D i bought a 28 small ear last year with a stiff cup and it took off great. bit like crazy. very little, if any cavatating. i was surprised how good it ran. i was only running 6 ins. setback at the time instead of my normal 12. the center sponson digs a huge hole while taking off, i dont see how any prop bites enough but they do. you may want to have it cupped and see what happens.

[David]

You could try adding some type of whale tail. Rickracers carries them. Cheap to buy and easy to install.

I added one to my Virage/XR4 and it completely changed how the boat planed with my over hub prop.