plumbing help
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plumbing help

  1. #1
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    Default plumbing help

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ID:	185427I have a carrerra 20.5 open bow jet boat that im putting a 7.4 merc cruiser mpi with a wipple super charger . My question is my old 454 didn't have a water pump on it and this new motor does, do I need to keep the water pump on it and if I do need it will the 5/8 feed hose from the jet drive still give enough water to run it . The hose from the water pump is as a guess 2 1/2 inch id . what could I use to go from the 5/8 hose to the 2 1/2 hose? It also has an oil cooler and fuel cooler built into the water plumbing system . The inter cooler also has 5/8 intake and dump hoses that I would like input on best place to plumb them into also please. I added a photo that may help a bit.
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    Last edited by Crazyjet1; 11-29-2012 at 09:16 PM.
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  3. #2
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    Quote Originally Posted by Crazyjet1 View Post
    I have a carrerra 20.5 open bow jet boat that im putting a 7.4 merc cruiser mpi with a wipple super charger . My question is my old 454 didn't have a water pump on it and this new motor does, do I need to keep the water pump on it and if I do need it will the 5/8 feed hose from the jet drive still give enough water to run it . The hose from the water pump is as a guess 2 1/2 inch id . what could I use to go from the 5/8 hose to the 2 1/2 hose? It also has an oil cooler and fuel cooler built into the water plumbing system . The inter cooler also has 5/8 intake and dump hoses that I would like input on best place to plumb them into also please.
    Well first of all make sure you change oil pans because the 7.4 mpi pan will not fit in the boat. 8 inches or less is the only way it will fit. I would loose the raw water pump and also the recirculating pump and plumb it like a jet boat. Thermo housing will have to changed to 2 outlet housing and replumb the dump water to the exhaust. Lastly this engine does not have a water pump sensor so pressure should not create any problems but the computer has to changed and take the cold start up mode taken out of it because it will stay in cold start up mode all of the time and run excessively rich at idle.

  4. #3
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    I'm guessing you have worked on one of them before?
    "A liberal paradise would be a place where everybody has
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    not, such a place does, indeed, exist: It's called prison."

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