5.7 volva penta help
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5.7 volva penta help

  1. #1
    Senior Member Mouzer's Avatar
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    Default 5.7 volva penta help

    My brother has a nice 1999 larson 23 ftr opn bow out drive deep v 5.7 GS volvo penta.....it runs wide open 3800 rpm it has a 2 barrel carb i toldem it should be faster and rpm out in the 4800 range........ Any input if a 4 barrel would help..thing runs awsome
    Last edited by Mouzer; 02-18-2015 at 07:10 PM.


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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Mouzer View Post
    My brother has a nice 1999 larson 23 ftr opn bow out drive deep v 5.7 GS volvo penta.....it runs wide open 3800 rpm it has a 2 barrel carb i toldem it should be faster and rpm out in the 4800 range........ Any input if a 4 barrel would help..thing runs awsome

    Any idea what propeller he is trying to pull?

    A four barrel will help, but you are not getting all 1000 RPM out of a carburetor and manifold change. If I had to guess, wrong prop choice, incorrect tachometer, tune up way off or water in the fuel.

    The difference form the 2V vs. the 4V is about 50HP.

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    deckboat owner rschap1's Avatar
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    Default x2

    Sounds like too big of a wheel on there too

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    Senior Member Mouzer's Avatar
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    what 4 b carb would you recomend ? would you get rid of the 2 barrel w/electric choke online the boat came with a 4 barrel model same motor it calls for a edlebrock 600 or something

    talked to the 1 owner who had it fist since new........prop has never been changed factory show room prop..i will get the size this eve.. the boat idles and runs smooth tachs out at 3800 smooth as a bell but my brother said at 1/2 speed it has a dead spot where it just cuts out you have to throttle passed it..what could that be.. carb/timeing/tune up boat sat for 6 yrs in storage covered nicely before he bought it... my brother changed the fuel out w/premium and some additives changed all the oils and gear oils carb off cleaned it he said it was in good shape idle pump worked good ect thought all this info would help.....1st owner said yes it should tachs out in the mid to high 4ks
    Last edited by Mouzer; 02-19-2015 at 01:54 PM.


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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Mouzer View Post
    what 4 b carb would you recomend ? would you get rid of the 2 barrel w/electric choke online the boat came with a 4 barrel model same motor it calls for a edlebrock 600 or something

    talked to the 1 owner who had it fist since new........prop has never been changed factory show room prop..i will get the size this eve.. the boat idles and runs smooth tachs out at 3800 smooth as a bell but my brother said at 1/2 speed it has a dead spot where it just cuts out you have to throttle passed it..what could that be.. carb/timeing/tune up boat sat for 6 yrs in storage covered nicely before he bought it... my brother changed the fuel out w/premium and some additives changed all the oils and gear oils carb off cleaned it he said it was in good shape idle pump worked good ect thought all this info would help.....1st owner said yes it should tachs out in the mid to high 4ks
    For the carburetor, I would say the marine version of the Carter/Weber AFB is a good choice, Mercruiser and Yamaha Stern drives used them. Should be able to find one used on the cheap.

    As for the dead spot, My bet is the carburetor has some scale and crap in it and needs a good cleaning. I would also caution on that old of a fuel pump, the diaphragms could be hardened and the pump very weak.

    These are just guesses mind you, but all worth looking into.

    Good hunting.
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Senior Member Mouzer's Avatar
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    thanks gt carb is off getting rebuilt if he doesnt find a good 4b and we will put a new fuel pump on it


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    Don't know if I'm breaking any rules, but iboats.com has an active volvo penta board....You may get your answers there....-Rich

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    I have a 24 donzi with the 5.7. I have the dual prop drive and I can get it to about 5400 @ roughly 50. It has fi though


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    kenny nunez
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    Post 3800 rpm

    One of the first things I learned in one of the stern drive schools was to be sure the the throttle is going to full open before checking everything else. That was in the early 70s. I never forgot that. I serviced Volvo, Mercrusier, OMC and Berkeley.

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    deckboat owner rschap1's Avatar
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    Default filter(s)

    When you say that the fuel was changed out, did the filter(S) get replaced?
    The water separator/fuel filter being clogged might be an issue...

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    Senior Member Mouzer's Avatar
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    Tank was empty when he got it and yes chaged out the water sep and fuel filter......


    As far as throttle goes my brother was checking it not running yesterday and when he thought was full throttle it kinda clicked then it went further then when on the lake..he thanks..


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    Quote Originally Posted by kenny nunez View Post
    One of the first things I learned in one of the stern drive schools was to be sure the the throttle is going to full open before checking everything else. That was in the early 70s. I never forgot that. I serviced Volvo, Mercrusier, OMC and Berkeley.
    Kenny has a very good point-always check the simple stuff first. To clarify a little - look down the carburetor to verify the throttle plate(butterfly) in the carb is fully vertical when the Throttle at the helm is at full throttle. Not opening fully can be caused by mis-adjustment, worn cable or linkage, bent brackets, binding etc.

    Also verify the tach is correct before chasing the RPM issue. Assuming the carb is reaching Wide Open Throttle and the tach is correct, the most likely reason it isn't reaching the specified RPM is to much prop.

    Doug

  15. #13
    kenny nunez
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    Default 3800 rpm

    A few other things I have encountered. An auto style air cleaner that was restricting, the customer put it on because it "looked good".
    Is this Volvo equipped with hydraulic trim, if not try moving the setting pin out to the next hole.
    Has the engine box been rebuilt, it may also be restricting, I once picked up 500 rpm on a customer's boat by opening the box.
    As already been said if you go the 4 barrel route make sure it is a marine version and use a dual plane manifold.
    Is the transom flexing? Stand on the out drive to see how much it will flex, that will also cause this problem.
    Good luck

  16. #14
    I like to turn wrenches
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    Mouzer, I know this thread is getting a bit old but how did your brother's boat turn out? Did he find that extra 1000rpm?
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