Using EFI and marine setup vs. car setup

Discussion in 'Powerboats' started by curtis73, Mar 13, 2002.

  1. curtis73
    Joined: Mar 2002
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    curtis73 Junior Member

    ...a little background first...
    I'm planning on building a 17' shallow vee speed/pleasure boat. I'm pretty much settled on the Glen-L Thunderbolt. I'm sure the standard powerplant is a Ford 302 or Chevy 350. I would rather keep weight down. Using my objectives, A logical choice would be a well-designed 6-cylinder. If choosing between a v-6 and an L-6, the V would take up more room in my small beam craft. THis makes me lean toward an L-6. BMW makes excellent L-6 powerplants, but their insane complexity and lack of low-end makes me stay away from them. AMC and Jeep used similar powerplants that sucked bad. Truck and older GM car sixes here in the states were iron anchors. GM just came out with a new 4200 L-6 for the trailblazer. Its all-aluminum, variable valve timing, four valves per cylinder, EFI and makes impressive power. I think its 270 hp and 275 lb-ft. Redline is well over 6000 and the torque curve is flat like Kansas. I don't know at what RPM the hp peaks.

    Is EFI usually kept out of marine applications? I know some of the larger new sportfishers use diesels that are very computer controlled.

    ...On marine engines vs. street engines...
    I'm a mechanic and car crafter, so I'm well versed in getting the right power for the street, but I'm no good at marine engines. Cars run at a low rpm on the road and downshift when the hp or torque peak is needed. If the HP peak in an street engine is 5200 rpms, where does it need to be in a marine engine? I've consulted many cam manufacturers who make "marine" cams. The cams seem to be just one-offs of a street grind. How about cooling. Just hook up water in and water out and let the thermostat do the regulating? Any special pump or thermostat?

    Thanks in advance
    Curtis
     
  2. Polarity
    Joined: Dec 2001
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    Polarity Senior Member

    Link

    Hi Curtis

    I'm a sticks and rags man, so 270hp in a 17ft boat is a bit of an amazing concept!

    Anyway you might fing this link to Lancing Marine useful, they list all the bits you need for marinising US and European engines as well as a bunch of other useful info.

    Cheers

    Paul
     
  3. curtis73
    Joined: Mar 2002
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    curtis73 Junior Member

    HP and length

    Well, its actually 17' 3"....that extra three inches make the difference. :D

    Thanks for the link

    Curtis
     
  4. curtis73
    Joined: Mar 2002
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    curtis73 Junior Member

    Actual HP

    One of the reasons I wanted to know about modifications for marine is that I'm wondering how many of them will sap power out of the engine. I want to use water heat exchange exhaust manifolds if I can make/find them. Depending on design, they will possibly restrict flow. I certainly won't be running it at redline all day, so I'll probably tune the prop to make it run around 5000 rpm. That will dramatically help long life. All of the above will most likely drop my power to more like 220. Untill it gets to the prop, it may be more like 185. Still lots for a 17' boat, but alot safer than 270.

    Curtis
     
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  6. curtis73
    Joined: Mar 2002
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    curtis73 Junior Member

    Great info!

    I'll most likely be using a GM 4200 vortec engine. I think its perfect. I may detune it a little so I don't kill myself as it comes factory with 270 hp. If I just tune it with a prop to keep it out of redline range, it will give me what I need. I think 180-200 prop hp is more like it. It is an inline 6 for space savings, all aluminum for weight savings, flat torque curve for getting my 250-lb. butt up on skis, EFI, and I may get lucky and find that they'll bolt up to many popular vee drives. The way I see it, if GM is using all of those engines in marine applications, and those engines use the same transmission as the 4200, (which they do) I may get lucky with a careful selection of parts and have a bolt-in.

    The only two things that plague me now are: How do I keep the ECM for the motor bone dry in a marine application? and Where on earth can I find marinsing parts here in the US for an engine that is brand new and no body has used in a boat before? I really want to make a cowl for the engine compartment, so a heat exhanging manifold is a must, what other parts?
     

  7. David Dobbs
    Joined: Mar 2002
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    David Dobbs Junior Member

    I am not a mechanic, and you probabaly know much more about this, but here's my 1 1/2 cents:
    I considered one of the aftermarket EFI kits, and they simply placed the electronics in a sealed box. I remember a note about the importance of careful placement of this, but I don't recall any serious problems. I did not end up going with the kit, so I'm only referring to my research as I was thinking of buying it, but have no direct experience.
    Good question, and probably one of the reasons that only a small number of engine blocks are used in a large number of boats.

    I think there's also a difference between marine engines intended for commercial/heavy duty use and those converted for recreational use (only 100 hours or so a season). In the latter case, the conversion is not really that extensive: marine carb, possibly different intake manifold (not necessarily) flame arrestor, shielded alternator, fuel water separator, marine water pump (and not always) with heavy duty marine impellor, water cooled exhaust manifolds. I think that's about it sometimes to convert to a marine engine.
     
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