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View Full Version : Need help with a 21ft Sanger????



FoMoCo
04-15-2001, 09:59 PM
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!!!!!!

spectras only
04-16-2001, 08:34 AM
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).]

FoMoCo
04-16-2001, 10:10 AM
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.!!!!!!!!!!!!

spectras only
04-16-2001, 10:52 AM
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.

FoMoCo
04-16-2001, 12:39 PM
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???

fat rat
04-16-2001, 02:13 PM
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

FoMoCo
04-16-2001, 02:47 PM
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?

spectras only
04-16-2001, 03:57 PM
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

LIQUID ASSETS
04-16-2001, 05:13 PM
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??

FoMoCo
04-16-2001, 06:23 PM
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?????

fat rat
04-16-2001, 06:37 PM
FoMoCo, it sounds like nothing got changed but your center of balance, I don't think it could be anything else.....I'd try the ballist idea before I got into any thing else.

fat rat
04-16-2001, 06:37 PM
FoMoCo, it sounds like nothing got changed but your center of balance, I don't think it could be anything else.....I'd try the ballist idea before I got into any thing else.

Caribbean19'
04-16-2001, 10:01 PM
Maybe you have already done this, but you could try calling Sanger and see what they think. Good luck.