Help. Getting beaten to death
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Help. Getting beaten to death

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    Default Help. Getting beaten to death

    Ok. I live in Alabama. I had never seen a jet boat until about 2 years ago. As soon as I saw it, I was hooked. But I don't know much about them. I finally found one in California that I liked. I had it shipped to Alabama. When I put it in the water, I was dying to stomp the pedal and see what it would do. When I hit about 30 mph it starts to porpoise. You can't enjoy the ride. Any suggestions for a newbie?

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Tras_h View Post
    Ok. I live in Alabama. I had never seen a jet boat until about 2 years ago. As soon as I saw it, I was hooked. But I don't know much about them. I finally found one in California that I liked. I had it shipped to Alabama. When I put it in the water, I was dying to stomp the pedal and see what it would do. When I hit about 30 mph it starts to porpoise. You can't enjoy the ride. Any suggestions for a newbie?

    Got any pics of the boat?, jets normally are fairly tuneable as far as ride quality unless there is something going on with the setup that won't allow the boat to "set" an example would be wedges, a rocker bottom, weight placement, lack of adequate horsepower (does the engine RPM stay stable?).

    A lot of times when this problem is experienced there is a chance it could be fixed/masked by a Place Diverter or some cav plates, Good luck!

    GT

    edit; welcome to the site!
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    The rpm's stay very stable. There is a manual trim adjustment on the jet drive, Originally it was trimmed all the way up causing it to porpoise at around 20 mph. I now have it trimmed down and picked up about 10 mph. I also added some weight under the bow. I do have some pics but I am having trouble getting them to upload. It is a 16 ft with a 350 engine. The drive is a jacuzzi (golden eagle?). I cannot find a model number.

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Tras_h View Post
    The rpm's stay very stable. There is a manual trim adjustment on the jet drive, Originally it was trimmed all the way up causing it to porpoise at around 20 mph. I now have it trimmed down and picked up about 10 mph. I also added some weight under the bow. I do have some pics but I am having trouble getting them to upload. It is a 16 ft with a 350 engine. The drive is a jacuzzi (golden eagle?). I cannot find a model number.
    A 16 foot boat I would think would respond well to some trim plates, manual ones should be good, just my opinion though, if it were me, I would install them as close as possible to the pump, they would not need to be very big, maybe 10"WX8" L,, I dunno...

    GT
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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    One thing I never considered about this style boat.... I've never seen one in Alabama. Unfortunately most of the boat mechanics around here have not either. One guy said I "might be able to put trim tabs on" but he wasn't sure. I will see if I can find some this week. Thanks

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    Where's the fuel tank ?

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    Senior Member Ol Man's Avatar
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    Quote Originally Posted by Tras_h View Post
    One thing I never considered about this style boat.... I've never seen one in Alabama. Unfortunately most of the boat mechanics around here have not either. One guy said I "might be able to put trim tabs on" but he wasn't sure. I will see if I can find some this week. Thanks
    A friend of mine had moved near Huntsville in the mid 90s with his 20 ft Howard jet. When he went to register it, they thought it had an airplane engine in it! He had to explain a bit more. They said it sounded like a jet ski, so that is how it was registered!

    He did get a lot of attention and questions whenever he would use it. Moved back here to California a few years ago.

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    If you would like to, you can email me pics of your boat to [email protected] and I will post them here in this thread for you. Most likely if you're having trouble the pics are too big and need to be downsized.

    Isn't 20 or 30 mph really early for a porpoising problem?

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by hotrod56cars View Post
    If you would like to, you can email me pics of your boat to [email protected] and I will post them here in this thread for you. Most likely if you're having trouble the pics are too big and need to be downsized.

    Isn't 20 or 30 mph really early for a porpoising problem?
    Indeed, but it is a small block and probably only a 45-50 MPH boat.

    GT
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    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Yeah I know.... It's a small block. But it's a start for me. It has 2 6 gallon tanks in the rear of the boat. They seem to be good for about 3 hours each. So I am definately looking to upsize the tanks at some point VERY soon. Hotrod, I'm emailing the photos now. Thaqnks to all of you for the help.

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    Large Member edog's Avatar
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    Do you have a ride plate? I had a 16 foot Caribbean. Just sold it. It did the same thing. I would cruise up river around 2500-3000 and it had the most annoying porpoise. I was able to get rid of it by lowering the ride plate about an 1/8" and was still able to free up the boat with a place diverter.

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    I may have a ride plate. What's that? There is a plate under the jet drive that is lowered as far as possible. Would a place diverter help this problem? I know that is what is used to throw a rooster tail which I want to get.

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    Senior Member jetboatperformance's Avatar
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    Tras the Pics you send of the boat should help alot , almost any of this can be corrected with hardware , didn't noticed in this thread but have you tried to work with the original equiptment "trim adjustment " at all ? is the porpoise violent or does the boat "bound slowly" ? Tom

    re the "Golden Eagle" the obvious identifier is the Square "cleanout" out side the hull/transom Tom
    Below is a G/E we did an "energizer on but the basic unit reains the same :

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Quote Originally Posted by Tras_h View Post
    I may have a ride plate. What's that? There is a plate under the jet drive that is lowered as far as possible. Would a place diverter help this problem? I know that is what is used to throw a rooster tail which I want to get.
    OK, you say there is a manual trim adjustment, EXACTLY what is it and what does it move on the jet or hull?

    All a "Place Diverter" is is a differnet brand nozzle assembly. While it is generally superior to original Berkeley parts, in several areas, it may, or may not help you here.

    The aluminum plate under the pump is the ride plate.

    Take a long straightedge, at least 4' (like a level), and look for several things UNDER the boat.

    Find out if the hull is flat, or if the bottom is curved in any manner.

    ROCKER, rounded like a rocking chair, is bad about porposing.
    HOOK, bottom slighly curved UPWARDS (reverse of rocker) tends to lift the rear, driving the nose down, causing drag, but adding stability.

    Find out where the ride-plate angle is in relation to the hull, angled up or down.
    Excessive down makes drag, excessive up fails to fight porpose.
    Consider the ride plate as a "stop" that the boat leans against when you have the diverter up making a tail, and making top speed.

    Now, separate from porpose, is HOPPING, not uncomon to jetboats.

    Where porposing pivots the hull at the back, HOPPING lurches the entire hull upwards. My Taylor used to hop, if tried to run at full down trim in the factory diverter. Lift the nozzle, bring on the tail, and the hop vanished and she smoothed out.I don't know the exact causatives to the HOP, physics wise, but it is a known phenomenae.

    Keep helping us with info, and we'll all do our best to help you out.
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