My buddy just purchased a 1981 21ft Sanger with a Berkley JE-A Pump, and we are having a problem with propoising. When he got the boat it had no motor, but it used to have an LS6. We installed a stock 454 about 300HP.(its also got a Jetovator and a factory ride-plate) The problem is that we adjusted the ride-plate down to make the propoising go away, but it only goes away when you run 2 people or less. Anymore weight like full gas and 4 people it just starts propoising like crazy around 20mph+. The jetavator is always in the down postion when running a heavy load because it just propoises worse when you put it up any! The weird thing is like I said you can ride in it with two people and put the jetavator all the way up and the boat rides perfect? I don't get it, whats wrong with this boat? how far on the ride-plate is to far down? Should we try CAV plates? HELP? this boat is bouncing us nuts!!!!!!
FoMoCo, it's normal for jetboats to porpoise at 20MPH,because you are below planing speed. A 20-21 foot jetboat will plane at 28MPH and up.That's the biggest drawback of a jet.The only way to keep the bow down at low speeds is to install a waterballast in the front with a high volume pump.
[This message has been edited by spectras only (edited April 16, 2001).]
It does it past 20mph also!!! it just starts there. I am guessing on the speed, but it could be more like 28mph when it starts porposing. It just gets worse the faster you go.!!!!!!!!!!!!
yeah ,it sounds odd that the boat porpoising past planing speed.Most 21 foot daycruisers have the opposite effect, ie; too level and too much vetted surface.Something wrong here .You could try a set of Bennett trim tabs, they are most effective but I never had trouble with placediverters either!You didn't mentioned if you have a droop snoot or wedges installed on your bowl.Too much upward angle could cause porpoising also.Too much weigth in the back could be the culprit too.
The JE-A pump is stock, but it does have a Jetovator. I have a set of good CAV plates to try on his boat. should We give those a shot? I just don't understand why a factory stock boat would do it! I don't see anything in the back of the boat that would cause it to have to much weight that is not stock! But It did help when 3 people sat up front instead of in back???
FoMoCo, this boat has been around for 20 years..what did the previous owner/owners say? Is the motor where the original was, or is moved foward or back some....just trying to brain storm a little here, Good Luck
My buddy bought it from some guy that sware his panther jet through-transom exhaust stock 460 has never been beat! The guy bought it for the blown-up LS6 that it originally had! We put everything back the way it was stock, or I think it looks that way! Does anybody have a 21ft boat with a Berkley JE-A pump?
The fact that a JE pump sets further than a JG or JC did reguire to put the engine further back, causing a heavier transom.Try to move your fuel tanks forward if it's a saddle type.It's a bit of nuissance if it's in the middle of the floor.Good luck
I have a 20' centurion that was bad about porpoising. what i did was move my two saddle tanks 18" forward havn't had a problem since.oyeah i plane at slower speeds now must have balanced the boat??
Why would it be this way from the factory? I mean I have no propblem moving the tanks but why was this not done from the factory? AM I missing something?????
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