Nordic Bubbledeck Porpoise Problems
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Nordic Bubbledeck Porpoise Problems

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    Junior Member Hot78Nordic's Avatar
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    Default Nordic Bubbledeck Porpoise Problems

    I purchased a 1978 Nordic Bubbledeck from my father-In law last summer, and I have been totally stoked on the boat with one exception. The darn thing has a serious porpoise problem at higher speeds from about 60 to the current top speed of about 75. I guess the problem was much worse at one time. My father-in law had a lot of work done to get it where it is at today. The guys at Jet Boat Plus in Havasu City blueprinted the bottom put on a droop snoot and made a custom ride plate for it. The motor is a BBC I believe bored to a 468 ci, Dominator pump, dual 750's with tunnel ram. The intake grate is stock and I was thinking of going to a loader grate. It doesn't really have a shoe, the ride plate is one piece and where it attaches to the boat it kind of looks like a shoe but I don't think it functions as one. The ride plate is not really adjustable, I believe it was at about 1.5 degrees up and I shimmed it down to zero with no significant results. I'm thinking now that I need to go the other way and maybe go to an adjustable plate. I would like to get a loader grate and maybe go to a straight snoot. I don't really know if I need a shoe and I don't really want to add weight to the bow. I know the boat will go faster than 75 but I just want a smooth ride at 75-80. When I put the place diverter all the way down it is much better but it plows and I don't get the speed I want. I've heard that the place diverter should be adjusted so you are putting a rooster about 3-5 feet off the water. Please help me out, this is an amazing ride and I just want to smooth it out a bit more. Thanks in advance for any assistance.

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    21 Daytona Outlaw's Avatar
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    Good luck
    I helped a friend try to stop his for years
    We could get it close but never cured

    We are actually going to put it back together once more after changing everything and adding several lavers of glass to make the rear 1/3 of the boat stronger







    Sent from my iPhone
    #55

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    pics of pump and back of boat or maybe of the shoe setup?

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    Junior Member Hot78Nordic's Avatar
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    I will post some pics tomorrow.

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    Senior Member rogerroost's Avatar
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    have you tryed it without the "rideplate",and droop. I've looked in to rideplates without shoe and have learned it really can't be done & work properly,may be doing more harm than good. Some boats just don't like a droop.

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    Junior Member Hot78Nordic's Avatar
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    Here are some pics:
    Attached Images Attached Images          

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    Junior Member Hot78Nordic's Avatar
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    I've taken the ride plate off and tried it like that and it was worse. Haven't tried without the droop, like I said it was once much worse without the ride plate, droop, and refinished/blueprinted hull. It feels as if the boat wants to come up higher and then either looses suction or has resistance and drop back down. Sometimes in rough water with the diverter all the way up I can get a smooth ride at close to top speed.

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    tintingsandiego krusn56's Avatar
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    Might try a straight HTP snoot with a 4 degree pin....
    Made In The Shade

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    Quote Originally Posted by rogerroost View Post
    have you tryed it without the "rideplate",and droop. I've looked in to rideplates without shoe and have learned it really can't be done & work properly,may be doing more harm than good. Some boats just don't like a droop.


    could you post a sideshot of the pump so we can see what that cradle looks like and a sideshot of your rideplate... could be bent?? Have you tried adjusting the plate? Looks like someone put alot of time into that setup, you should call jetboatplus and see if they still remember the boat? Also put a straightedge on the biting edge in relation to keel and also see if you might have developed a hook in the boat again by checking that with the straightedge also. just a thought.
    work with what you have there before investing in another part that might not help.

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    Senior Member 19ftDana's Avatar
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    Is it just the view or does the ride plate look really long? How long is that ride plate?

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    Senior Member BrotherWolf's Avatar
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    Having the diverter all the way up will lift the bow up and will porpoise more on some boats, have you tryed a wedge yet?
    With Spray there is a way!!!

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    21 Daytona Outlaw's Avatar
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    looks like you have on of those "add on " ride plates. I've seen a couple of these before,( a homemade shortcut to add a ride plate).
    problem is it really doesn't give you any adjust ability on how much water you're feeding the pump.
    First thing I would do is remove the intake and have it machined for a shoe and ride plate or replace it with one already machined.

    when you re install it make sure you set it at the correct angle, this will depend on which intake you have.
    with a shoe you can adjust the opening on the intake, probably overcharging the intake currently.

    I was told Nordics were built with a Hook into the bottom, we removed the hook my friends, currently we have a new intake from MPD ready for install.
    but his project has been on hold for a couple years. Once we put it back together I'm confident it will run out lots better.
    #55

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    Default porpoise

    I found that the porpoise issue is usually related to a weight balance problem. Have you tried moving the engine? Does the boat act differently with more or less people in it? I had a porpoise problem in my boat and ended moving the engine to solve the problem.

    Good Luck

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    Senior Member DuaneHTP's Avatar
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    Throw a bag or two of water softener salt, or something of equal weight in the back of the boat against the transom, (about 50 or 60 lbs on each side), and see how it reacts. Then report back here.

    Duane HTP

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