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DCA
05-09-2002, 03:47 PM
Hi,
I wondering if anybody has any ideas on how to solve a very difficult porpoise problem that I have been dealing with.
I am running a 1977 Pioneer with a BBC 468 and Berkley E Pump with a Dominator Droop Snoot/Place Diverter. The engine is turning a stainless A impeller. I start to encounter the porpoise problem at around 60 mph(speedo).
I have tried everything I can think of to solve the problem. I took the hook out of the bottom. I have used the place diverter in various positions. I have tried the ride plate in different up and down positions(trim). I have moved the engine forward in various tests until it was 6" ahead of it's original position(balance). I tried a shoe. I even tried raising up the intake of the pump by 1/2 of an inch above the keel line(over charging).
At this point I am running the intake at 1 inch below the keel line. This has settled the boat down along as I don't go too high on the place diverter. A soon as I let off the throttle, the nose wants to dig in(intake drag).
I would like to get the boat stable at high speed.
Any ideas?

Jetboatguru
05-09-2002, 03:59 PM
Alot of the fisherman use gill nets to stop unruly porpoises. I am against this as I have always loved Flipper. Please understand that the water is theirs and we are only visitors.
[This message has been edited by Jetboatguru (edited May 09, 2002).]

DEL51
05-09-2002, 06:43 PM
I have heard that engine location has an affect. maybe, if the weight distribution isn't right, this is your problem.I have also heard of people rounding off the sharp edge of the shoe.

wsm9808
05-09-2002, 07:48 PM
with 2 or more more passengers in my boat it will porpoise quite a bit at around 40 and you cant trim it out with the diverter. But with no load(no riders or gear) it is extremely smooth with no hint of porpoise at any speed. Dont know if that will help you any, but maybe wieght distribution changes might help. Do a "search" in the Cats & tunnel fourum, they had a lenghtly discution on porpoising a few months ago.
welcome to the board
[This message has been edited by wsm9808 (edited May 09, 2002).]

froggystyle
05-09-2002, 07:53 PM
One easy thing you might try is to remove the droop snoot. It is not for every hull, and I have heard of increased porpoise on some.

greg shoemaker
05-09-2002, 08:01 PM
Froggystyle Good advice not all boats like a lower thrust line. It seems to me that in the old race days the Pioneer did not use a droop snoot and ran very well. All you need is a nozzle housing and your in busines. Greg

jet496
05-09-2002, 09:37 PM
I just installed a droop snoot on my boat & noticed porpoising (I did gain some interesting performance though). Nothing too bad, but I haven't had much chance to test it. I will this weekend though...The River baby!
Try taking it off & see what happens.

HBjet
05-09-2002, 09:39 PM
What about throwing a few sand bags up front? I know RiverDave has to do that with his Nordic. It had very bad porpoise problems because the X dim is off.
HBjet

Licketty Split
05-10-2002, 06:30 AM
In removing the hook was any rocker put in it by mistake

cyclone
05-10-2002, 09:44 AM
Hey Greg, I was considering a droop snoot on my boat but I've hesitated to buy one because I dont want to develop any porposing. My hull is a '71 Rogers Cyclone and right now I have almost no porposing. What do you think? I have a place diverter and was looking at the new droop snoot and ride plate combo from Place. I've heard that I should go with a custom ride plate and pull my intake out to have it installed and not use the one from Place. Does that one just bolt on? it looks like a lot less work.

Licketty Split
05-10-2002, 09:56 AM
It is a lot less work when I blue printed my bottom I broke mine while pullim it and had to weld it back up but now I think it was worth it

froggystyle
05-10-2002, 10:02 AM
I'll let Greg field his own question, but my two cents are this... It is absolutely bolt-on, adjustable and relatively inexpensive. I have seen it work, and recommend them to my close friends.
Not to mention completely reverseable, and re-sellable. Although I have NEVER heard of someone regretting the addition of a "real" ride plate.
Squirts up.

RiverDave2
05-10-2002, 11:07 AM
Originally posted by HBjet:
What about throwing a few sand bags up front? I know RiverDave has to do that with his Nordic. It had very bad porpoise problems because the X dim is off.
HBjet
Actually the X-Dimension is not the reason it has pourpose.. (Atleast I don't believe it is)
RD

Bense468
05-10-2002, 02:03 PM
Cyclone do you have a split bowl? If you don't which I don't think you do then you will need one to install a droop. I have looked at the drrop with the ride plate. I think it will work to some degree but I don't see much adjustment in it. If you really want to optimize your ride a full ride plate is probably the best route. It will take some time to get the best results though. I suggest a GPS. The last I heard you were pulling some decent numbers with that olds.

DCA
05-10-2002, 03:00 PM
Originally posted by DCA:
Hi,
I wondering if anybody has any ideas on how to solve a very difficult porpoise problem that I have been dealing with.
I am running a 1977 Pioneer with a BBC 468 and Berkley E Pump with a Dominator Droop Snoot/Place Diverter. The engine is turning a stainless A impeller. I start to encounter the porpoise problem at around 60 mph(speedo).
I have tried everything I can think of to solve the problem. I took the hook out of the bottom. I have used the place diverter in various positions. I have tried the ride plate in different up and down positions(trim). I have moved the engine forward in various tests until it was 6" ahead of it's original position(balance). I tried a shoe. I even tried raising up the intake of the pump by 1/2 of an inch above the keel line(over charging).
At this point I am running the intake at 1 inch below the keel line. This has settled the boat down along as I don't go too high on the place diverter. A soon as I let off the throttle, the nose wants to dig in(intake drag).
I would like to get the boat stable at high speed.
Any ideas?
Hi,
I appreciate all the feedback. I am going to be on the water on Saturday testing.
Thanks

1quickjet
05-10-2002, 04:13 PM
Greg, I have a question too, if I may. Same question as Cyclone's. You know my boat has rocker. I removed the wedge and got rid of the porpoising at cruise speed, but that seems like a lot of down nozzle just to cruise, doesn't it? It works though. I was wondering if a droop would cause more porpoise on this hull. By the way, the boat takes a nice set at speed (WOT)! Any porpoise is only at 3000 rpm or so. Thanks! Jeff

LVjetboy
05-11-2002, 02:50 AM
One easy thing you might try is to remove the droop snoot. It is not for every hull, and I have heard of increased porpoise on some.
Well...if adding droop increases porpoise (lowering thrust line), flipping the droop upside down should reduce porpoise (raising the thrust line) Possible? Seems a rather "non-obvious" direction to go http://free.***boat.net/ubb/smile.gif http://free.***boat.net/ubb/smile.gif
Also may scr*w with your top end...
Actually the X-Dimension is not the reason it has pourpose.. (At least I don't believe it is)
Must be those neons then, eh RD? Oops, thought this was jet "talk" not jet "tech"...confused as usual...my bad. No flames here. I get the talking and teching confused.
carry on

greg shoemaker
05-11-2002, 07:53 PM
With a real ride plate and shoe assembly you can set the bitting edge of the shoe at a very percise setting above the keel. With the Placediverter droop rideplate assembly you get the rideplate with no shoe depth and that's the whole purpose of a ride plate and shoe assembly.The droop will lower the thrust line and that will give you lift in the boat and in turn that will give you more speed. When I tested the unit on plane time was improved with the rideplate and top end speed was increased with the droop. More speed can be increased with a shoe because the amont of water to the pump can be increased or taken away by changing the depth. Greg

cyclone
05-14-2002, 08:56 AM
Ok that makes sense. What about the bolt on shoe and rideplate that Hi-tech Performance sells. If i understand correctly, you drill holes in the intake and bolt the shoe to it and the rideplate bolts to the pump. Has anyone ever gone that route and what were the results? I watched a video of my boat running wide open the other day and it ran pretty wet. I'm trying to get it out of the water.