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Questions from a newbie

  1. #1
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    Default Questions from a newbie

    Hello All,

    I recently bought a project boat, an 89 Wellcraft 20' daycruiser. It had an outdrive and the guy I bought it from was in the process of converting it to a Berkeley jet and cut the hole for the jet already.
    He's a pretty good fabricator so the work is clean, but I only got the jet with no transom cover which is no big deal since I can buy one used, but I had a few jet drive questions.

    I don't know the model of my Berkely, but which is the best setup as far as impeller type and what not for performance? Also is there a peak efficiency as far as rpm for these impellers? If so I'd like to put as small a V8 as possible to save fuel while still being able to reach peak rpm for the pump.

    Alot of these terms are new to me, I'm a novice boater but I have built engines for many years so bear with me while I learn from you guys.---Jim

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    Senior Member Brendellajet's Avatar
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    Got pics? If you are looking for good fuel economy, put the outdrive back in. Jets are less efficient than pretty much everything else out there, though there are things that can be done to make them less inefficient. Not many running small blocks, though the GM LS motors seem to be doing well. Keep the efi and it might work out for you. You will want to research engine tolerances as they pertain to boats because there are a few adjustments you need to make.
    "He is a lover, not a fighter. But he's also a fighter, so dont get any ideas."

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    Senior Member ICECREAMAN's Avatar
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    In general pumps like torque and hp. The amount of power and where in the rpm range your motor developers its peak power will determine the optimal size of impeller you would want to run. Small blocks in jet boats are more of an oddity than the norm because you still need good torque to make a pump work, and it's easier to get good torque numbers out of a BB.

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  6. #4
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    Default Small blocks

    Quote Originally Posted by ICECREAMAN View Post
    In general pumps like torque and hp. The amount of power and where in the rpm range your motor developers its peak power will determine the optimal size of impeller you would want to run. Small blocks in jet boats are more of an oddity than the norm because you still need good torque to make a pump work, and it's easier to get good torque numbers out of a BB.
    Small blocks work quite well in SMALL jet boats... Very small, very light. In just about any other jet, there is NO substitute for cubic inches.... I'm wondering about the bottom of an "in/out" vs the bottom of a jet? All the power in the world MAY be a huge disappointment unless, and until, the bottom sees some changes...Usually these 1/2 done projects are 1/2 done for a reason....And there are a bunch of them out there, 1/2 (or less) done....
    Ray
    LOUD BOATS SAVE LIVES

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    Quote Originally Posted by Moneypit View Post
    Small blocks work quite well in SMALL jet boats... Very small, very light. In just about any other jet, there is NO substitute for cubic inches.... I'm wondering about the bottom of an "in/out" vs the bottom of a jet? All the power in the world MAY be a huge disappointment unless, and until, the bottom sees some changes...Usually these 1/2 done projects are 1/2 done for a reason....And there are a bunch of them out there, 1/2 (or less) done....
    Ray
    Well if worse comes to worse, I only paid $1000 for it and the trailer is worth more than that, so I'll just get another boat for my trailer or sell the trailer, but I have to try before I give up and I'm not born from fearful men... so once more into the breach!
    Good point about the bottom though, I may have to contour the thing to ensure a smooth uninterrupted intake stream.

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    Quote Originally Posted by ICECREAMAN View Post
    In general pumps like torque and hp. The amount of power and where in the rpm range your motor developers its peak power will determine the optimal size of impeller you would want to run. Small blocks in jet boats are more of an oddity than the norm because you still need good torque to make a pump work, and it's easier to get good torque numbers out of a BB.
    Thanks for the info.

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    Quote Originally Posted by Brendellajet View Post
    Got pics? If you are looking for good fuel economy, put the outdrive back in. Jets are less efficient than pretty much everything else out there, though there are things that can be done to make them less inefficient. Not many running small blocks, though the GM LS motors seem to be doing well. Keep the efi and it might work out for you. You will want to research engine tolerances as they pertain to boats because there are a few adjustments you need to make.
    Thanks

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    While I'm at it I might as well ask what is the difference between an A impeller and a B impeller? Thanks

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    Senior Member motomattox's Avatar
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    Check out the thread "Jet Boat Acceleration." A couple of the guys on here loaded up some pretty good charts on impellor RPM and a lot of good info. Also pretty entertaining read . I have to say, small blocks don't tend to be the best choice for boats much over 19ft, but it really depends on the motor output and your expected/desired performance levels. If you know what your want the boat to do, MPH wise, list it on here and I'm sure you'll get 30 opinions on how to accomplish it. The LS is getting all the love on here, but your a mopar man....any 5.7 HEMI in your boat's future????
    "Keep talking...it aint often I get to hear a genius speak"

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    Quote Originally Posted by motomattox View Post
    Check out the thread "Jet Boat Acceleration." A couple of the guys on here loaded up some pretty good charts on impellor RPM and a lot of good info. Also pretty entertaining read . I have to say, small blocks don't tend to be the best choice for boats much over 19ft, but it really depends on the motor output and your expected/desired performance levels. If you know what your want the boat to do, MPH wise, list it on here and I'm sure you'll get 30 opinions on how to accomplish it. The LS is getting all the love on here, but your a mopar man....any 5.7 HEMI in your boat's future????
    Well I'd love to throw a Hemi in there but I have a 500 horse 360 sitting there on the engine stand doing nothing...along with a 383, a 440 and a 505 stroker, all wedge motors, so the Hemi will have to wait.
    I've also got a couple of 454's lying around as well so you never know, it seems that chevy parts are more plentiful as far as boats go, just like cars.
    MPH wise, hell I'd like it to do 120, but 80 would be reasonable as far as engines go, I can build whatever is needed HP wise, just let me know how much it will take so I know in advance.

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