Page 1 of 3 123 LastLast
Results 1 to 10 of 23

Thread: Blower on "Pleasure Boat"

  1. #1
    H2O
    Hello,
    I have a question about putting a blower (Whipple or Procharger) on my stock 7.4/300hp carburated Mercruiser. I am only looking for modest power gains (say 40%) and I would keep it within stock RPM limits, since the motor has cast pistons, 2 bolt mains, etc.
    My question is this: When I prop-up, to take advantage of the extra HP on top, will the boat be a dog out of the hole?
    At what RPM do these kits start to make boost? (assuming I'm pulley'd for 5 psi) Is this is good choice for an "all around boat" where I still want to do a little skiing and maintain decent cruising MPG and reliability.
    Thanks to all!!!

  2. #2
    djunkie
    I'd say 40% is quite a bit more than modest.

  3. #3
    VDRIVERACING
    IMPORTANT - Outdrives are really expensive. Remember that your outdrive was spec'd for the torque output of your current engine. Depending on your increase in power (don't count on 40% more), you may only need to upgrade a bearing set, or shaft, or you may find out your unit will not handle the extra torque at all. But researching this aspect is a must before you spend a dime on your powerplant.
    To answer your question, most superchargers will increase your low end power. A roots-style blower, like the Whipple screw drive, will provide you with power right off idle, whereas some of the centrifugal units will have some lag, but probably hardly noticable in your application.
    My impression is that you have a stock boat, and want more power without a complete make-over. I have heard a lot of good things about the centrifugal units lately, and they fit neatly under your current engine cover. I suggest you call the competing manufacturers, and get some specs and price trade-offs. Also ask them about materials, warrenty, life expectancy, and what other components need to be upgraded/changed.

  4. #4
    ghittner
    Good advice above. I've been running the same Bravo One drive unit since 1989 and have serviced it yearly. I have done no upgrades and it has lasted through three 454's, 1-330HP, 1-500hp, 1-650hp and now I've blown a 498 @ 800 or so HP with a season 50 Hours or so, on the same drive, no work on it yet. Be nice to the drive, it's not a drag car or a stump puller and it will last you a very long time. I currently and in the past run my set ups at up to 6800 RPM for extended periods. Hope that helps.

  5. #5
    H2O
    Thanks guys, good stuff so far.
    I have called around to the manufactures and dealers and discussed their products. Of course I take that with a grain of salt, since they are all trying to sell you something. I am especially interested in what real world users have found in the day to day operation of their boats.
    I was under the impression that a Bravo One could handle 400 + horsepower if treated gently, as ghittner seems to confirm. While I admit that 40% is not a modest power gain in general, it is modest compared to what the maunufactures are claiming on this engine.
    http://www.procharger.com/M_engine.shtml
    Procharger is showing 465-525 hp on a stock carburated 7.4 and I was saying I would be happpy with 400 to 425. (Partly becuase I don't believe everything I read and partly beacause I don't want to break anything).
    Thanks again, keep the good info coming...

  6. #6
    DMOORE
    Like the guys above have stated, a lot of how reliable these systems are( for the motor and drive) is how they are used. If you do not go too crazy with the boost, your motor can easily handle a supercharger. The bravo drives will handle the power as well. Just remember, no WOT hole shots. Roll on the power when coming on plane, and roll off when coming off plane. As far as when the boost comes on, all supercharger types and systems are a bit different. I have a roots type blower on my motors that make 10PSI. At a cruise speed of 3500RPM my motors are still pulling vacume ,and live a very easy life. The prop is yet another part of the puzzle. You should be able to find a nice prop that will still alloy a good planing time, and give you some good top end. A lot of the boats that I have seen that went the same mild supercharger route you are looking at, have seen roughly a 10-15MPH increase.
    Darrell.

  7. #7
    VDRIVERACING
    A lot of good info from these guys.
    I have never, ever, heard somone regret the addition of a supercharger. Installed properly, and operated with good judgment, your motor should remain reliable and smooth operating.
    As a matter of fact, you're ahead of the game by starting with a lower performance motor, because the cam will be better suited for a blower, than a HP cam for a carbureted motor would. The biggest difference from your cam and a blower specific cam, would be a longer exhaust duration.
    One final thought: make sure your crankcase ventilation is in good order, and increase your oil change interval. I don't know how fresh your rings are, but by their nature, blowers tend to drive more intake charge past the rings during boost. A small price for what should feel like a new engine.

  8. #8
    Infomaniac
    Not to be a spoil sport or anything ..... but you have the worst engine to bolt a supercharger onto. It works great as designed but does not take well to the extra power. An additional 40% in my opinion would be too much to live very long.
    Great input from everyone.

  9. #9
    franky
    Same experience with the Bravo, be nice to it and it will take the power. Had a Cole with a 7.4 330hp upgraded to about 400, then 500 then added Vortech, ran like a banshee till the cast pistonn gave up (you will rape your motor too). Built it back up w/forged averything, 800 dyno hp, no problem on the Drive. Boat now has a smaller motor but same drive 13 years later.
    Couple things, go with the Vortech, much nicer (refined) kit than the Procharger. Definitely have an intercooler. Vortech makes a nice carb box (I made mine) and expect to spend a lot of time getting the carb set up right to work under pressure (the whole thing). Think about this, carb in a pressurized box, 10 pounds of boost (I had 13 at 6K), so now you have 7 pounds of fuel pressure trying to overcome 10 pounds of pressure. So yeah, you boost reference the regulatar. OK now what regulator/fuel pump likes to go over 17psi? EFI reg, but they dont like to start at 7 and (ref boost) to to 17. I ended up with a Paxton (aeromotive) EFI pump feeding a (Paxton) EFI reg set to 35 (with a return) feeding a Mallory reg boost referenced. Worked great but VERY Frankenstineish.
    If I had it to do over again I would have never messed with a blow through carb set-up. However, once dialed in it was turn key, idled at 600 rpm, fit under the hatch (sleeper) and ran like no tomorrow. It was fun making it work and very different. ( I made my own BIG intercooler using Spearco cores)
    So with all that said I would say if you are set on carbs and a blower, Whipple and the Bravoo will last if you don't punch it out of the hole, roll it on plane then get after it. Don't get air and then romp it on the landing, blah, blah, blah.

  10. #10
    ghittner
    Just a thought here.... I too was nervous about the blow through set up. So much so that I went with a roots style B&M 420 even though I had to raise my hatch 5". From the day I started it until now, it has been very simple, straight forward and tuning is a breeze as the carbs are working as they were intended, drawn through. no problems to date whatsoever..........And, it looks really bitc$#n when you open the hatch...

Page 1 of 3 123 LastLast

Similar Threads

  1. New toys for my ***boat pleasure!!
    By TRUMP TIGHT in forum Sandbar
    Replies: 0
    Last Post: 09-19-2006, 05:35 PM
  2. For Bent the terrorists listening pleasure!
    By Steve 1 in forum Political Phetoric
    Replies: 1
    Last Post: 12-15-2005, 02:41 PM
  3. Pleasure To Meet Everyone
    By LAFD in forum Sandbar
    Replies: 2
    Last Post: 06-28-2005, 10:37 AM
  4. For Your Drinking Pleasure
    By SoCalHD in forum Sandbar
    Replies: 18
    Last Post: 10-01-2004, 01:31 PM
  5. Update on Jungle's pleasure boat
    By Jungle Boy in forum Jet Boats
    Replies: 18
    Last Post: 02-29-2004, 09:42 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •