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Thread: Advise on getting more low end power...

  1. #1
    I have a 18 footer with a legend jet drive and a 4.3 V6 mercruiser (chevy) motor. This motor has the stock 2BBL Rochester carburetor with a rather tiny flame arrestor. I have the following questions:
    1) Would spending 120 bucks on a bigger K&N flame arrestor really make a difference in this carb?
    2) In order to get more power, which way would I be better off going:
    a) change the carb to another 2BBL (I am looking at the Holley 300 CFM Two Barrel part# 0-80320-1) and keeping my existing intake manifold, or
    b) go with a 4BBL holley 600 CFM part#0-80492 and incure the cost of replacing my existing intake with a 4BBL intake.
    Please keep in mind that this is just a family boat and all I am trying to do is to get the kids up on skis and have no intention of racing or anything like that.
    Thanx in advance for all recommendations...

  2. #2
    flat broke
    First off welcome to the boards. Before we get started, get ready for the responses telling you to swap out to a SBC or BBC powerplant. Assuming that your mercruiser setup does not have any sort of electronic fuel management system, the mods you propose are a good start. In a bang for the buck scenario, I'd say that the 4barrel with new manifold will take you the furthest. Cost wise the 600cfm carbs are usually less than the comparable 300/390 cfm two barrels. The $120 you could spend on a fancy K&N breather will go a good ways towards purchasing a new intake manifold. When you have those parts installed, make sure you do get a flame arrestor that will breathe better. The standard Stainless Wire unit will do you fine for $60-$80 bucks. However, there is no sure way to know that these mods are going to give the 4.3 the extra umph it needs to get your kids out of the water faster. But within the bounds of your question, I would say go with the 4 barrel and manifold combo. There are tons of ways to get more power, but you can cross that bridge when you get to it. Out of curiosity, will your boat pull your kids up now? If it's just slow yanking em out, I'd say smaller mods should get you heading in the right direction. If you can't pull them up at all right now, there is a good chance that just a carb and manifold probably won't do the trick.
    Good luck,
    Chris (

  3. #3
    Flat broke,
    Thanx a lot for the advice. Good point about getting bunch of seggstions in this bulletin board on droping a 350 or a 454 in my boat. Beleive me, I've heard it way too many times and don't get me wrong, I do agree. However, I really don't have the space for even the additional 4 or 5 inches required to put in a 350.
    As I said, it is a fairly small boat and even a smaller cockpit; the only way to upgrade to even a 350 motor means that the boat goes from a 4 seater to a 2 seater, and that's not an option (it being a family boat).
    At any rate, I will begin looking into some pricing on the 4BBL carb and a 4BBL intake. By the way, I hear that Edelbrock also makes this combination for a 4.3 chevy. Do you have a preference for Holley over Edelbrock? I think that pricewise, they come out about the same.
    Thanx again bud...

  4. #4
    Racing Ray
    [This message has been edited by Racing Ray (edited March 18, 2002).]

  5. #5
    Don't get my wrong, I can get the kids up with no problem. I'd just like a bit more low end to get them up a bit faster...

  6. #6
    flat broke
    Whew, I'm glad to hear you're able to pull them out of the water as it sits right now. As for the Holley vs Edelbrock question. I'm sure if you did a survey on the board it would fall about %80 Holley/Demon, %15, Edelbrock/Carter, and %5 Predator/other for the carb guys. I like Holley, but thats because I have been working with them since I was 14 or so. You can always pick up 600 Vacum secondary Holleys on Ebay for less than an Edelbrock because of their abundance. Plus since there are more guys running them, there is a bigger pool of information to pull from regarding troubleshooting tips.
    Hope that helps,
    Chris (

  7. #7
    I'm brand new to this forum. I do have a similar set up as yours. A 4.3 Volvo with a PJX volvo jet drive. To get a little more power off the line, I replaced the D cut impeller with a C (legend). I do however have a 4 Barrel Holley. I spent a lot of $$$ on a Cavitation Reducer prior to changing impellers and did not notice a significant improvement.

  8. #8
    69 Elim
    Since you have the 4.3, and intake and carb are the way to go. But, don't for get the cam. I have a S10 with the same motor and I read an article which by swapping cams picked up about 50hp (not bad from the origional start at 185hp). This should get you the power your looking for.

  9. #9
    miller killer
    I used to have a 4.3,their good motors,if you have the time and money a good machine shop can off-set grind the crank and put a small journal rod on it and build a stroker motor.

  10. #10
    Kiwi Legend Jetter
    Hi Jet Drive...
    What impeller are you turning now? And at what rpm?
    I have heard (but have not witnessed for myself) that a cavatation reducer works very well for holeshot/skiers. Anybody else seen one in action?
    Don't feel bad about your 'small' engine. I'm building a boat which will be powered by a flat six subaru and legend pump. (I'm off to put on my firemans suit for the flaming to come!!!! http://free.*** )

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