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  1. #31
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,218

    Default Re: V6 to V8 engine swap

    Quote Originally Posted by pappymarty View Post
    I am trying to replace a 4.3L with a 360 ci V8. Is there an after market mount that will make up the additional length using existing mounting holes?
    Ayuh,... Welcome Aboard,... Ya mean a 350,..??

    I believe ya might have to swap the y-pipe to align things,....
    There's also various elbows, that go 'tween the risers, 'n y-pipe,....
    Any Grease is Better,... Than No grease at All....

  2. #32

    Default Re: V6 to V8 engine swap

    Thanks. 350 is correct. Hate those senior moments. I have the exhaust covered. The last thing is the front mounts. I could have something fabricated but thought there may be an after market extension that would use the existing holes.
    I am trying to stay away from drilling into the fiberglass. The structure for the motor mount stops short of the 350 mount.

  3. #33
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,194

    Default Re: V6 to V8 engine swap

    Marty, you will have better end results if you do not try to shortcut this.
    I'd suggest that you cut into your existing engine mount stringers, and extend them forward.


    .
    Last edited by RicardoMarine; 01-20-2016 at 11:59 PM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  4. #34

    Default Re: V6 to V8 engine swap

    Thanks Rick, I'm in uncharted water here.

  5. #35
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,194

    Default Re: V6 to V8 engine swap

    Quote Originally Posted by pappymarty View Post
    Thanks Rick, I'm in uncharted water here.
    The waters are charted, perhaps just not by you.

    Post a few photos of your engine bay. One of us can help you.
    Also, maybe you will be able to find a YouTube video showing something similar being done.
    It is not all that difficult to do, and most people do better than what the factory did!

    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  6. #36

    Default Re: V6 to V8 engine swap

    Thanks but it will be Spring before I uncover this thing. More time and better weather. Problem has been, when I had time to work on the Sea Ray I had time to use the Bass Tracker.
    Thanks I'll get back to this.

    Marty

  7. #37

    Default Re: V6 to V8 engine swap

    I'm just finishing a 5.7 conversion into my '88 SeaRay Seville BR. It's been a ride! Yes you'll need to extend the motor mount bunks about 4.5". It wasn't hard, if you have any fiberglass experience (google will make you an expert! LOL)... I went to the local lumber store and picked up a scrap of 8x8 pretreated lumber... then cut it to fit my extension area... then supported with a slurry of fiberglass filler, then glassed over the block to match it to the original bunks... then Gel-coated... Looks totally OEM. I've been trying to do this on the cheap... but here's the details... EFI system from a 97 Mastercraft... Cam from the same motor... Rebuilt Jasper 5.7 Roller Vortec... V8 center riser exhaust manifolds (3" version - Uggh!)... These fit right onto my existing 4.3L "Y" pipe. I'm still hoping to find a 4" exhaust manifold set... One hassle so far has been rewiring the Mastercraft plug in (they use a 5x2 flat connector configuration)... However the biggest pain for me is the "high pressure" fuel pump, pre & post filters, and return line... I finally have a workable solution in my head, and expect to complete it by July 15 or so. I did pick-up a 1.50 ratio outdrive, and will put a new impeller and seals into it before installation.

    HERE"S MY QUESTION... Where should I start with proping my new 5.7L setup?

    With my 185-4.3L (1.84 outdrive ratio), I used a SS 14.25" x 18 prop... Max RPM was 5100 when trimmed perfect. I tried at least 8 different props before picking that as my best overall solution (near best out of the hole, best to 20mph, near best top end).

    Also, considering the extra weight and extra power... does anyone have a thought of what to expect in terms of increased performance?

  8. #38
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,218

    Default Re: V6 to V8 engine swap

    Ayuh,.... Start with the prop ya got,....

    With the taller gear ratio, it might be dead on,.....
    Any Grease is Better,... Than No grease at All....

  9. #39

    Default Re: V6 to V8 engine swap

    Any thoughts about performance impact... will it be dramatic or ??? I really don't know what to expect. The boat is a deeper V design and is somewhat heavy already.

  10. #40
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,218

    Default Re: V6 to V8 engine swap

    Ayuh,.... Goin' from a 4.3l to a 350 will be Noticeably more powerful,....
    Any Grease is Better,... Than No grease at All....

  11. #41

    Default Re: V6 to V8 engine swap

    "NOTICIBLY MORE POWER" will make it worth the effort! I did get it fired up on Saturday, it sounded wonderful! The fuel delivery system was a bit of an effort. Going from a single line mechanical fuel pump... to an electric high pressure EFI fuel pump, with High pressure fuel lines, clamps and fittings... plus a return line. To complicate matters, my donor boat (97 Mastercraft, was an inboard... and had all the fuel delivery at the motor's back end.) I learned alot! Do you think I'll need to insulate the fuel lines as they pass near the water pump and over the intake manifold? The lines are good for 300 degrees F., and 250 psi.

    Tonight I was building new seat platforms for the 2 jump seats that flank the engine cover. I had reconfigured the rear of the boat somewhat to gain better access. Before it was IMPOSSIBLE to get to the Plugs, wires, Oil drain plug and Oil filter because the engine compartment had side walls quite close to the exhaust manifolds. Those walls supported the rear jump seats, but ended up being a MAJOR PIA. Now they're gone... ) And access is far easier. And you can be calmed in that they were obviously not structual in nature.

    Do you have an opinion on the lower half of the outdrive as far as 1/R vs the MR? I have both, and both will fit onto the 1/R 1.50 upper. The MR lower is from the 4.3L install and I think I'll use that... unless someone would advise differently. I understnd the MR unit was redesigned with a bearing cup under the waterpump base plate. Thanks to all for the input.

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