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Thread: HELP WITH VOLVO 5.7Gi

  1. #1
    slovolvo
    Hi Everyone,
    I am new to this forum, and was wondering if any one could offer me any advise(other than a swap=)) for my volvo motor. Here is the deal, the boat is a 2005 Outlaw 21' with a 2005 5.7 liter Gi (280 hp) motor. The outdrive ratio(if anyone is wondering) is 1.51:1. For a prop, I have had the best luck with a three blade 21 pitch aluminum. With this combo, I have hit 58 mph(wind at my back, farting), and can consistantly hit 55 at 4200-4300 rpm (WOT). With a 19 pitch prop, the motor reved out to its 5k redline, but I lost over 5 MPH.I would really like to see the boat hit the 65-70 mph range. How can I get there? I have found that there is a real lack of aftermarket part support for this motor. Some of the mods I am looking to do are, trim tabs, through transom exhaust, headers, and possibly a blower.
    Any help or insight is greatly appreciated!

  2. #2
    SoCal_fun
    I'm impressed with my Stingray 22 then, as I get 63.5 on gps with the 320hp 5.7gxi and a 21 SS prop. I have also tried the 19" 5 blade and redlined the motor with a loss of about 3-5 off top end (great for skiing though).
    I haven't seen any mods for this engine. :cry:

  3. #3
    slovolvo
    Yeah, I wish I had the Gxi, that would be a start for sure. It sucks having 280hp and getting smoked by bass boats! Fortunately, things like trim tabs are kind of universal, so I should be able to get more of the boat out of the water pretty easily. That is the first mod I am going to do. Other than that, it looks like its going to have to be all custom. I will let you know if I find anything. In the meanwhile, hopefully someone chimes in with some help....

  4. #4
    jmherbert
    Doubt you'll see that speed unless you pull it, stroke and work the heads. Or, look for a blower/supercharger and hope the guts hold up

  5. #5
    SoCal_fun
    Doubt you'll see that speed unless you pull it, stroke and work the heads. Or, look for a blower/supercharger and hope the guts hold up
    I sure wish they would put out a procharger kit or whipple kit fot it.

  6. #6
    slovolvo
    I bet someone could make good money building hi perf Volvo motor parts..........

  7. #7
    jmherbert
    i don't know much about Volvo's fuel injection and/or brain box, but at the end of the day they are still small block Chevy 350's, I would guess that any mods that work for Merc 350's (or any SBC) could be made to work for the Volvo's
    Oh, by the way, I've seen bass boats run in the high 90's, and a lot of the ones with 200+ will run at least in the high 70's. Outboards give more 'bang for the buck' as far as the horsepower:speed ratio, not to mention those hulls are light and purposely built for 1 reason.... MPH. In fact, a lot of their hulls are basically copies of old Hydrostream outboard race boats

  8. #8
    slovolvo
    You are exactly right about the motor being a SBC. I just wonder if all of the bolt patterns(exhaust/intake manifolds) would be the same. My understanding (from talking to a tech) is that the computer is the same one used in Chevy Vortech motors. If this is indeed the case, it shouldn't be too hard to get some more power.
    BTW, does anyone know the difference between the Gi and the Gxi? How does that motor make 40 more HP? Bore, stroke, and compression are all the same. Anyone know? That might be a good starting point.
    Bass boat are really amazing these days. I was in a Bass Cat years ago on Lake Castaic and we did 83 on GPS! I guess you could say we were haulin' bass. Ok, bad joke.
    As I get into the motor issue more, I will post on here. I think I am going to get the boat out this weekend.

  9. #9
    YeLLowBoaT
    my guess the only diff is some EFI magic... diffrent fuel curve, long pulse width, timing and etc. Then again they could have diffrent injectors, intake or cam.

  10. #10
    antonmies
    I have a Penta AQ225 which is an SBC 305. All the bolt patterns etc. are the same. Only differrence is that it has a 350 crank in it.
    I guess that the 40hp is based on a differrent program in the ECU. If I were you, I would turbocharge it and put a mild 7psi of boost in it. But I'm mad... :crossx:
    I guess that Vortech has some universal supercharger kit for an SBC. I think that you should find out.

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