SeaArk OB to Jet conversion
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SeaArk OB to Jet conversion

  1. #1

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    Default SeaArk OB to Jet conversion

    Got an 1872 (18' long 72" bottom width) modified V SeaArk with a 70HP Johnson. It is basically a flat bottom in the back and a v in the front. Very stable boat for bowfishing.

    Already got my hands on a Berkley 12JF pump and have a SB Chevy 400 that I am going to rebuild with alum heads. Not planning to get crazy with the hopups for the engine right now. I would be happy if it ran 40 mph but might have a heart attack if we get 50 out of it.

    Got a whole ton of work to do but being able to run super shallow and avoid all those underwater stumps will be worth it. Plus go fast is always a good thing. My buddy has already converted his boat and learned what not to do when mounting the jet in the boat.

    Think my my speed hopes are realistic? My biggest concern is cavitation while on plane.

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  3. #2
    Senior Member jetboatperformance's Avatar
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    Hulls with "flat bottoms" do not take well to jetdrive conversions for a multitude of reasons , if the bottom of your project at the rear keel area is truly flat you may have some "loading' and handling issues. If the hull has some dihedral (V) (you indicated a "semi V" ) it might be a good project. Not familiar with the "name" but some pics might help We have done sucessful Jet conversions on IO's OB's and several Jet to jet (Panther to Berk etc) Due to the neccesity for a mold insert or extensive glass work I'd conside a 12j c'g'etc vs the "E" to simplify your project Post up or call if we can help Tom

  4. #3

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    Thanks for the reply. Maybe these old pics will help.

    I should not say it is completely flat at the back but you can tell it is pretty close. The V goes about halfway up the hull and mostly flatens out the back. Notice also the stringers (sorry might not be the correct name) that stick down the bottom of the hull where the alum is bent for strength. I was not sure if these would cause problem with cavitation or not.
    The jet will also allow the fan to be mounted lower on the transom rather than above the outboard and wont have to deal with a 2 stroke OB any more. This is a bowfishing boat and we fish/hunt at night with lights and generator running.

    My friend put a Berkley jet in his 1660 and mounted the engine under the center console but it had too much weight forward. Even like it was he was doing 40 before it would start cavitating. He admits to mounting the intake wrong on his boat though. In my boat I want to keep all the weight as far back as I possible to take advantage of the flat bottom. Plus I will build sponsons (float pods) on the back to help offset some of the weight. The main reason for the 12JF is because it allows you to mount the engine about 12" further aft than the 12C...and the jetavator is built in.


    http://www.bowfishtexas.com/images/boat/rearboatfan.JPG

    Another
    http://www.bowfishtexas.com/images/boat/boatwrail.jpg

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  6. #4
    Living in a cage of fear thatguy's Avatar
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    What is the fan for?

    We used to run some wicked BBC Air Boats w/ variable pitch props, in Alaska, but have never seen a "combo" before!
    Tommy
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  7. #5

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    Bowfishing....the fan replaces a trolling motor so there is nothing in the water but the hull. It can go over weeds and small brush and does not get hung up or muddy up the water like a troller would. It is only a 24HP Honda engine so it is no airboat but you would be surprised how many people ask how fast it goes!

  8. #6
    "Try it Now!" Tahiti Boss21's Avatar
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    dude!, i'd get drunk on that boat and end up in the blades, guranteed!
    1992 Eliminator Daytona 21'

  9. #7
    Senior Member jetboatperformance's Avatar
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    Sorry ,just doesn't look like a good candidate for a Jet IMO

  10. #8
    mo balls than $cents$ IMPATIENT 1's Avatar
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    Quote Originally Posted by jetboatperformance View Post
    Sorry ,just doesn't look like a good candidate for a Jet IMO
    imagine the work involved with making a insert pump seal up in that thing be tuff but a good fab guy could do it.


    why not just convert the outboard with a jetpump lower half? all the bowfishermen here have all converted to outboard jet. funny looking units but they move the boats well and hardly have any draft.

    Dare to be different, if it turns out great you can claim you planned it that way.

    Jetboatperformance.com

  11. #9
    Senior Member 2002CP19's Avatar
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    That is one ugly boat.

    Good luck with your build!

  12. #10
    Senior Member bajadad's Avatar
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    Quote Originally Posted by Tahiti Boss21 View Post
    dude!, i'd get drunk on that boat and end up in the blades, guranteed!
    X2 that cuz where from Yucaipa.....lol

  13. #11
    Bouncing off rocks TryMe's Avatar
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    dont listen to these guys, not many people on here actually run skinny water, mostly guys with lake boats that wouldnt dream of beaching their boat on a gravel bar etc.

    that boat wont handle very well at all compared to a v bottom. you probably have less than 10 degrees in the back of that hull. shoal runnner has been building v8 jets in jon boats like that for 20 years. i see jets just like that every weekend out here in the midwest, most have 350 sbc with an A impeller, most run about 50-55, but they dont steer real well.

    i think youd be much better off with a 125- 150 powerhead with a jet conversion. from experience i can tell you a loaded v-8 john boat takes at least 2 extra guys to drag off a gravelbar than one with a whacker motor. either way, i wouldnt try to run more than 60 in that hull
    Last edited by TryMe; 05-31-2009 at 10:11 AM.

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