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  1. #1

    Mercury 4.3 liter with Alpha 1 sterndrive ???

    Helping a friend get some performance from his boat. He's got a Late model Bayliner 185 bowrider with a Mercury 4.3 liter V6 (looks like a Chev product with factory Merc mods) and I belive a Alpha I sterndrive currently running a four-blade 20 pitch Aluminum prop.

    I haven't alot of experince with boats, but have built many skidoo and pick-up truck engines. My first thoughts are this thing needs some AIR. I think he needs to install a cold-air-intake to replace the stock restrictive underhood intake, does mercury or aftermarket make something?

    Next we need to get some cool air under the hood as well, the stock under-hood-exaust-fan is a joke, where can we get vents that will let in air but no water? And a fan that moves some air?

    And he wants to try a 23 or 24 pitch 3-blade prop for some speed, as the current 4-blade 20P is great for skinig, but "revs out" when Wide open.

  2. #2
    The Mercruiser 4.3 is a chevrolet engine. On the air intake subject, the boat should have a coast gaurd aprroved/required spark arrestor. Be safe and use it. You can clean it with degreaser and its as good as new. They flow very well. Your exhaust fans are for removing any fuel vapors that may have collected in the engine compartment, not so much for inducing cold air in. You can get various forms of vents from Overtons or West Marine. As far as props go a 20P sounds like an awful lot of wheel for a 4.3. A three blade stainless will probably score you better results. What RPM are your turning at WOT ?

  3. #3
    Join Date
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    performance from his boat....

    what are your final goals???
    The wife likes it too! When shes happy I'm happy

    2003 Cougar 22MTR w/300xs
    90 21Skater w/300xs - sold
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    2006 Trailblazer SS 6.0l 395hp
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  4. #4
    Join Date
    Aug 2005
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    port orchard , wa
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    Find some used vortec heads,there the best bang for the buck on the 4.3s.Depending how far he wants to go a mild Comp Cams wakes them up as well.The vortec heads are a big improvement and probably will be just what hes looking for.As far as doing a air-intake setup,itll make more noise but not much more power.Id find some factory vortec heads for a couple hundred, throw them on and be done with it.

  5. #5
    Join Date
    Mar 2003
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    Belvidere IL, FARM
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    6,962
    Quote Originally Posted by Euroski View Post
    performance from his boat....

    what are your final goals???
    To get it to plain out and hit 30 mph
    God, Country, and Fast Boats
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    Live your life that the fear of death can never enter your heart. And when your time comes to die, be not like those whose hearts are filled with fear of death, so that they weep and pray for more time that they may live there life over in a different way. Sing your death song, and die like a Hero going home.

  6. #6
    Quote Originally Posted by aaronmt73 View Post
    Find some used vortec heads,there the best bang for the buck on the 4.3s.Depending how far he wants to go a mild Comp Cams wakes them up as well.The vortec heads are a big improvement and probably will be just what hes looking for.As far as doing a air-intake setup,itll make more noise but not much more power.Id find some factory vortec heads for a couple hundred, throw them on and be done with it.
    He says it's a "late model" boat, so it more than likely has Vortecs on it already. I do agree with the Comp cams idea. Good call.

  7. #7
    Join Date
    Aug 2005
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    865
    I wouldnt assume it has the vortec heads.Most 4.3 marine boats dont.If it does itll say it on the valve cover.Only way id think it would is if its a injected 4.3.Most bayliners wont be that way unless ordered with it.If its a carb motor and doesnt say vortec on the valve cover more than likely its not vortec.

  8. #8
    It may not have them but, either way I agree with you on Vortec heads. They are some damn good heads.

  9. #9
    Join Date
    Feb 2009
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    Edgewater,B.C. CANADA
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    Try a High Five prop around 19" if its 0-30mph performance your after, have lots of 16-18' Bayliners and Sea Rays around here and they work well with that prop.

    Dave
    1980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
    1988 BAJA Sunsport 186, 96 225 Pro Max
    79 12' Auminum, 95 Merc 9.9
    RIP Stu
    "So many idiots, so few bullets"

  10. If It have a two Barrel carb Mercury had earlyer model's with a for barrel Rodchester an better in take, , an bringing your engine temp down to 140 deg rather that the 160 deg of your stock t stat will alow cooler air flow tho the engine aswell

  11. #11
    Join Date
    Aug 2007
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    Be carefull with the Vortec heads. They made two different bolt patterns. Just make sure they match your existing manafold or you'll be buying a intake as well.
    Bud Conner "Heathen Supporting Our Constitution"

    FOR ALL ENGINE APPLICATIONS
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  12. #12
    Join Date
    Jun 2004
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    port st. lucie, fl
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    most of the later 4.3 stuff was vortec, if it isn't a vortec as bud said you will have to buy an intake, 1.6 ratio roller rockers would be an easy swap, and something you probably notice. if this thing is relativeley new it would also have a roller cam, whcih adds quite a bit of cost to a cam swap, and also, vortecs are limited to .480 lift without removing material from the top of the valve guides, as well as requiring a valve spring change. a 4 barrel intake would be a good start as well.
    action mobile marine, 772 528 0754, dealers for aces fuel products,wolf efi, pro marine,latham and gaffrig/livorsi. we build gearcases and modify them(3 litre) to ratchet, and powerheads as well. 21 skater/3 litre wolf efi the engine build http://www.screamandfly.com/showthre...-3-litre-build

  13. #13
    Thanks guys. It's a 2006 Bayliner.

    The engine is throttle-body fuel injected and breathes hot underhood air through a funny-lookin air cleaner (someone above called it a spark arrestor) that is only about 8" in diameter and 1-1/2" high ... You guys are saying to not mess with it ??? we would just like a kit to funnel cool air to it.

    Engine currently revs to 4800 -5000 at WOT. Not sure of the torque and Hp numbers for the 4.3, however I'm sure she's got the "gutts" to pull a bigger / lighter prop, as the engine sounds like it's "reved-out" and not pulling hard anymore. I know with Outboards one can expect to gain approx 150 rpm per pitch when changing props. Is this true also for a 4-stroke sterndrive?

  14. #14
    Join Date
    Aug 2007
    Location
    North Eastern North Carolina
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    6,648
    If it's a 06 then it's a vortec engine. The 4800/5000 is the correct operating range for that engine at WOT. They made two HP ratings for that 4.3 190 and 225. Don't know which one you have. Yes leave the Flame arrestor alone it's on there for a reason and if you get stopped for a inspection and it get's noticed it is no longer there you will get a citation.

    You can try a higher pitch prop the engine may have the Nuts to spin one. You'll just have to try.

    As far as a fresh air kit. Don't know of one. You'll have to get inovative and fab one yourself.
    Bud Conner "Heathen Supporting Our Constitution"

    FOR ALL ENGINE APPLICATIONS
    DRY Film Lubricant for Piston Skirts & Cranks + Thermal Barrier Ceramic Coatings for Piston Tops, Combustion Chambers, Valves etc !!


    Banner Compliments of Pete Woodworth!!!




  15. #15
    Ya I won't remove the flame arrestor, sounds important. We were just trying to plan a syestem with some shark-gill-intakes on the side of the boat and funneling it to a sheet metal box that fits the flame arrestor. The engine cowling is a sun-pad so we don't wanna place a hood-scoop up there. But we are concerned with potential water entering the shark-gills in rough water, so we may make a tee so the cool air can be shut off if needed.

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