Page 1 of 2 12 LastLast
Results 1 to 20 of 22

Thread: High performance build on a 5.7(350) Chev marine engine

  1. #1
    Member
    Join Date
    May 2015
    Location
    Alaska
    Posts
    4

    Default High performance build on a 5.7(350) Chev marine engine

    I have a KEM Equipment 5.7 in my 21' jet. I think it's a little under powered at 260 HP. I'm thinking of trying to find someone here in South Central AK that might be able to take my engine and squeeze it up in HP to about 375-400. I keep wondering if that would work or would I be better off dropping a 383 stroker in there. Any thoughts on the best option? My 350 has only about 40 hours on it. What would it take in $$$ to tweet that engine? I'd like to do it this winter when the boat's idle. I don't have the knowledge to do it myself.

  2. #2
    Member Yukoner's Avatar
    Join Date
    Aug 2007
    Location
    Whitehorse Yukon
    Posts
    1,342

    Default

    Are you running a carb or FI 5.7? Short of a super charger, I don't think you'll get those numbers out of a 350. Everyone who has a 383 seems to really like the power. Have you checked out the Mean Chicken site? Lots of HP type guys on there and some good input. Haxby Speed in Vancouver pretty much lives and breathes this kind of stuff and might be worth a phone call.
    If it was me, I guess I'd just run it until I needed a new engine. I wouldn't say you were underpowered with a 5.7 in a 21' boat. It's going to cost you some $$ to get more power. Seems like lots of guys are eagerly awaiting the new Ford marine engines. I bet by next winter or so there might be some good deals on low hour 6.0s and similar as guys swap out their GM mills for the new Ford engines.
    Never wrestle with a pig.
    you both get dirty;
    the Pig likes it.

  3. #3
    Member theultrarider's Avatar
    Join Date
    Mar 2009
    Location
    Soldotna
    Posts
    1,096

    Default

    Imo you would be money ahead to pull your low hour 350 and sell it. Drop in a new 38 built how you like and have a warranty.

  4. #4
    Member DanielApplin's Avatar
    Join Date
    May 2013
    Location
    Palmer, AK
    Posts
    344

    Default

    Ya not worth having someone work on that engine, by a zz383 or a supercharger.

  5. #5
    Member
    Join Date
    May 2015
    Location
    Alaska
    Posts
    4

    Default

    Thats pretty much what I expected, the 383 stroker at 375 HP seems to be the block of choice. I believe I'll run the 350 this summer then swap out for the 383 this winter. Thanks for all the input, it really helped solidify my thoughts!

  6. #6
    Member DanielApplin's Avatar
    Join Date
    May 2013
    Location
    Palmer, AK
    Posts
    344

    Default

    Don't look past a new 6 liter or ls3 either depending on your funds

  7. #7
    Member Yukoner's Avatar
    Join Date
    Aug 2007
    Location
    Whitehorse Yukon
    Posts
    1,342

    Default

    The new GM engines KEM is showing look amazing. The 5.3 VVT is rated at 355 HP. Love to know the weight on it. I bet they'll be real cheap too......
    Never wrestle with a pig.
    you both get dirty;
    the Pig likes it.

  8. #8
    Member
    Join Date
    Aug 2007
    Location
    palmer
    Posts
    167

    Default

    The 5.3 will be about the same as the aluminum headed 6.0

  9. #9
    Member DanielApplin's Avatar
    Join Date
    May 2013
    Location
    Palmer, AK
    Posts
    344

    Default

    The 6 liter makes way more power at a lower rpm that most pumps are suited for than that 5.3 di

  10. #10
    Member DanielApplin's Avatar
    Join Date
    May 2013
    Location
    Palmer, AK
    Posts
    344

    Default

    Not way more power..... But a little I guess it's closer than I thought. Any power curves for that engine yet? And known costs?

  11. #11
    Member For Pete Sake's Avatar
    Join Date
    Apr 2006
    Location
    Dawson City,Yukon Territory
    Posts
    60

    Default

    I swapped out the kem 350 carbed 310 hp for a zz383 stroker 425 hp coupled to a 3 stage kodiak pump. Cheaper to buy the crate engine in a long block.

  12. #12
    Member
    Join Date
    Jan 2008
    Location
    Anchorage
    Posts
    895

    Default

    Just wondering. What do you want more horsepower to do for you? More top end speed, better hole shot, carry a heavy weight when out of your secondaries, able to get a heavy load on step at all, fuel economy (not likely)?

    For every gain there is a draw back it seems. More top end speed means you spin the pump faster. Push a heavy load and you may need more displacement in the engine and/or more RPM's. You can also tweak the impeller. What is your pump? I have mine set up to push as much water as it can at the 3300 RPM area with a hopped up 351W. My 3 stage has a bigger nozzle and more pitch in the impellers. It slows the boat down some but it increased the amount of weight I can keep on step for a long Yukon trip. Just saying, there are other ways to squeak out performance without spending $10k or more on a new motor.

  13. #13
    Member Yukoner's Avatar
    Join Date
    Aug 2007
    Location
    Whitehorse Yukon
    Posts
    1,342

    Default

    Quote Originally Posted by For Pete Sake View Post
    I swapped out the kem 350 carbed 310 hp for a zz383 stroker 425 hp coupled to a 3 stage kodiak pump. Cheaper to buy the crate engine in a long block.
    Hey Pete
    How did that work out for you in the end? Did it turn into the 2 Moose boat you had hoped? Is the pump holding you back at all?
    Never wrestle with a pig.
    you both get dirty;
    the Pig likes it.

  14. #14
    Member For Pete Sake's Avatar
    Join Date
    Apr 2006
    Location
    Dawson City,Yukon Territory
    Posts
    60

    Default

    Worked out great, better hole shot, pushes more of a load 10 adults, lower rpms, swapped out 3 impellers, 35 mph upstream, 47 mph downstream, stays on step at lower rpms too 3400, wide open 4100, getting better fuel mileage with the stroker vs the plain 350. You can put all the hp you want into a boat but it comes down to fine tuning your pump also.

  15. #15
    Member DanielApplin's Avatar
    Join Date
    May 2013
    Location
    Palmer, AK
    Posts
    344

    Default

    What impellers and nozzle for that kind of performance

  16. #16
    Member For Pete Sake's Avatar
    Join Date
    Apr 2006
    Location
    Dawson City,Yukon Territory
    Posts
    60

    Default

    Kodiak 3 stage came with front impeller 19*, middle 19*, rear 22.5* ran good but had a lot of rpms with the stroker engine so swapped out front impeller to a bullet nose 19*, middle to a 22* and the rear to a 27* also running a Scott trim adjustable trim nozzle with a 98 mm nozzle. The 3 stage pump really shines when there are a lot of sticks in the river, chews them up and spits them out, I have seen other pumps disabled by getting debris stuck in their pumps and having to winch the rear of the boat out of the river to dislodge what ever was in there. All impellers are stainless steel last set I had lasted 10 years they are pricey but worth it in the long run.

  17. #17
    Member DanielApplin's Avatar
    Join Date
    May 2013
    Location
    Palmer, AK
    Posts
    344

    Default

    I'm running a bullet nose 19 Scott, then 23 and 24 with a 100m&m nozzle with a 350 and pull 4300rpm at 45-46mph
    I've been debating building a 383 or getting the zz383 for the future and am contemplating if it's worth it. Do you run 91 octane?

  18. #18
    Member For Pete Sake's Avatar
    Join Date
    Apr 2006
    Location
    Dawson City,Yukon Territory
    Posts
    60

    Default

    No just running regular gas, tried the high octane but didn't notice any difference, I am going to try a bigger nozzle 108 mm an see what difference that makes.

  19. #19
    Member For Pete Sake's Avatar
    Join Date
    Apr 2006
    Location
    Dawson City,Yukon Territory
    Posts
    60

    Default

    Get the crate engine less headaches, all u need to do is swap out intake and manifolds, alternator, distributor, took me about 6 hrs to do.

  20. #20
    Member For Pete Sake's Avatar
    Join Date
    Apr 2006
    Location
    Dawson City,Yukon Territory
    Posts
    60

    Default

    Your set up looks like it works nice with you getting those speeds, what length of boat are you running?

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

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