questions from a newbie

Discussion in 'Powerboats' started by alabama mike, Aug 19, 2013.

  1. alabama mike
    Joined: Jul 2008
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    Location: Cullman, alabama

    alabama mike Trying to learn something

    please forgive me if this is posted in the wrong spot, and forgive me if the questions sound dumb, All the boats I have owned up to this point have been outboards, I just got a 1969 22 ft Reinell, it has a mercrusier (250 chevy) and a mercrusier out drive, the motor is bad, I have a friend that will give me a 5.0L (305 chevy) mercruser motor, but he doesn't have any of the cooling parts, its just a long block, My question is if I put this motor in can I run dry exhaust and a radiator?, I would like to be able to trailer the boat to the coast and run the inter-coastal water way. My thinking is with a radiator I wouldn't have to worry about salt water damage, and if I did this could I just block the water intake on the foot? does the foot need the water for cooling as well as the motor? again forgive me if this sounds dumb, I've worked on cars for years and I've had boats for years but this will be the 1st boat that I haven't had to mix 2 stroke oil in with the fuel!
  2. IMP-ish
    Joined: Jan 2011
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    Location: united states of america

    IMP-ish powerboater

    A radiator needs enough airflow and it will make the cockpit loud. Your exhaust system has water to cool it and redoing it dry stack will also make it loud. Easier to buy the marine exhaust risers and elbows, carb, alternator, starter. The auto water pump will work for a circulating pump for a while then replace it with marine.
  3. alabama mike
    Joined: Jul 2008
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    Location: Cullman, alabama

    alabama mike Trying to learn something

    louder that a 2 stroke outboard, LOL, I see what you're saying, guess I was thinking on trying to make it work with what I got here!
  4. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    Too bad about the 250. That is what I have in my 1972 Sea ray and it is a very good engine. What you need if you are going to use your boat in both fresh water and salt water is a heat exchanger. It works basically the same as a radiator but is designed specifically for boats. The parts are readily available both locally from dealers, and on the internet through outfits like and There are lots of others who sell these parts. This will give you a quiet and well cooled engine. It is well worth a little extra for the parts.

    PS: make sure your sterndrive will be able to take the added torque of the 305, because you maybe also looking at a stronger sterndrive.
  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yes, you can run your engine with a dry exhaust, but you'll need a keel cooler or heat exchanger to handle a "sealed loop" engine coolant setup. Set your 305 to produce no more then 200 HP if you want it to be reliable and not blow out the Alpha. Lots of places to get the appropriate cam for this change.

    The dry exhaust will need to go up and out of the engine compartment, typically with headers mounted upside down. Of course this is loud, way more then that 2 stroke, but you'll be sitting in front of the noise and driving away from it, so it will not be as bad as you think. Of course, the folks around you (other boats, folks on shore, etc.) will think it's damn loud.
  6. alabama mike
    Joined: Jul 2008
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    Location: Cullman, alabama

    alabama mike Trying to learn something

    Thanks guys, I'm looking up the heat exchanger and keel coolers, now. I do like the idea of a closed system. If I go this route is it safe to block off the incoming water in the stern drive? and what would be a good way to do it?
  7. mike165
    Joined: Nov 2011
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    Location: wagga OZ

    mike165 New Member

    It's not an Alpha but a R,or MC1 and good for 300HP the fly wheel cover of the 250 will fit the 305 or 350 I did the same on a early Bayliner,the gears on the 250 are 1.1.65 you need
    1.1.50 for the V8 and use wet manifolds
    P.S. the 250 is easy to rebuild and cheap,watch the riser they block easy
    PPS if you do the closed cooling use the pump in the drive and run it out thru the manifold

  8. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The gears and oil in the drive get cooled by the water running through the pump into the engine and out. You will have to reroute the water somehow too.
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