my first jet and I have ?'s
+ Reply to Thread
Results 1 to 9 of 9

Thread:
my first jet and I have ?'s

  1. #1
    Junior Member
    Join Date
    Jul 2010
    Location
    Valley Springs
    Posts
    11

    Default my first jet and I have ?'s

    I've been around jets and I/O's my entire life, but this is first running one that I've owned. 73 Spectra 20, 454 and 12jc.

    It runs really well, I picked it up not to go fast but to hall the family around. That being said I want just a little bit more.

    The background I was given from the original owner of boat:
    15yrs ago pump rebuilt stainless impellor (confirmed) unknown cut
    5yrs ago flat'nd cam complete top end rebuilt (no specs)
    last year motor rebuilt compression droped from 12:1 down to 10:1
    motor has a nice single plane weiand and the original 780 holley vac sec.


    Unfortunatly, even though the boat cam with a nice little folder with the original sales brochure, reciept and some other really cool history kinda stuff. I have no actual data on the motor specs or cam specs.

    The boat gets out of the hole pretty good for its size, but tops out at only 4500rpm ( i keep forgeting the GPS to get MPH ) and cruises really nicely at around 33-3500rpm. Are there any little tricks to squeazing out a few more rpms, I'd really like to pick up the pace just a bit.


    *before its brought up, I've been pouring over new and old threads (heavy search button) but all i see is put more money into it. I know there's got to be some jet boat tricks out there.

    Thanks,
    Justin
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	DirtyOar.jpg 
Views:	75 
Size:	286.7 KB 
ID:	81595  

  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    NorCal HotBoats Chili's Avatar
    Join Date
    Aug 2009
    Location
    Chico / Paradise
    Posts
    532

    Default

    There are no tricks, just put more money into it. lol
    74 Belmont - 455 - Berkeley

    Facebook - NorCal - Local Chapter of American Hot Boats

  4. #3
    Screamin SeaMonkees Schi-502's Avatar
    Join Date
    Jun 2008
    Location
    Vacaville, California
    Posts
    1,663

    Default

    Quote Originally Posted by Chili View Post
    There are no tricks, just put more money into it. lol
    Yeah, what he said!
    Loose, the Dogs of War!

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    Member Dave01's Avatar
    Join Date
    Sep 2008
    Location
    NH
    Posts
    66

    Default

    The 2 things I'd look at:

    1) you don't mention if it has a jetovator or Place Diverter on it. If not, you have to add one, it will add speed and general driving fun and control.

    2) carb - original Holley vac secondary - has it ever been rebuilt? If not, you might want to be sure its set up and operating well, might be worth a rebuild.

    And yes, everything you do will cost money!
    '86 Eliminator Sport 20, Chevy 454, Berkeley 12JG w/jetovator

  7. #5
    NorCal HotBoats Chili's Avatar
    Join Date
    Aug 2009
    Location
    Chico / Paradise
    Posts
    532

    Default

    Agreed, Carb would be the first thing i would look into.. but its going to cost something, maybe not much but something.

    If you want to pick up some RPM or MPH for free, toss out the back seat. lol
    74 Belmont - 455 - Berkeley

    Facebook - NorCal - Local Chapter of American Hot Boats

  8. #6
    Junior Member
    Join Date
    Jul 2010
    Location
    Valley Springs
    Posts
    11

    Default

    I'm working on finding a PD. There is one up by woodland in my price range, but he doesn't list what pump it came off, just the two pumps it wont fit.(legend and JE)

    I thought about rebuilding the carb, the secondaries were gum'd up a bit. The boats been sitting for over a year. So I dumped some marvel mystery oil in the tanks. Thank god the tanks were just about empty and still smelled like gas, so its running on fresh 91 octane and 16 oz of MMO per 24 gal. So every run gets better and better, but the rpm's are staying the same.

    I'm just trying to gather good concrete suggestions. For winter upgrades that dont require kidney removal.

  9. #7
    Senior Member Sanger Pete's Avatar
    Join Date
    Feb 2008
    Location
    Clovis/Shaver Lake
    Posts
    156

    Default

    If it is a AA impellor, the rpms sound about right for a basically stock BBC and that would also account for a good hole shot.

  10. #8
    Senior Member jetboatperformance's Avatar
    Join Date
    Dec 2007
    Location
    Atascadero Calif
    Posts
    7,464

    Default

    Quote Originally Posted by DirtyOar View Post
    but he doesn't list what pump it came off, just the two pumps it wont fit.(legend and JE)
    .
    This would mean that it pretty much fits virtually all Berkeley type Jets except the "insert" JE and JF (external cleanout), Place Diverter Trim is without a doubt one of the best "bang for Buck" bolt ons you can buy for your Jet boat Tom

  11. #9
    Member clarkph's Avatar
    Join Date
    Feb 2009
    Posts
    76

    Default

    I just rebuilt my pump a Dominator 12S similar to a berk, , mild 330hp 454, "A" impeller, 4600 rpm on the nose just like the chart/graph said.
    50 mph tops on the speedo. I need more RPMS and mainly $$$ HP!
    Check out American turbine's website, they list the proper rpm vs hp vs impeller size, lots of other tips too. americanturbine.com
    A Place diverter does help a lot, I can really feel the boat pick up speed as the nozzel/trim comes up.

    You need to know what impeller (AA, A, B, etc) you have, a Stainless Steel Imp. is for 500 hp and above I have heard, and an AA is probably too much for that boat it's not exactly a lightweight, but a good family boat.
    You need 425 HP to turn an AA @ 4600 rpm per the charts.

    I received great advice from Tom at jetboatperformance.com he walked me through the rebuild and sold me the parts, great guy...I cannot believe how simple and reliable a jet drive is. (never had one before)

    Good luck and have fun!

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Please select your insurance company (Optional)

Log-in


Digg This Thread

Posting Permissions

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95