Thread: Johnson "70mod"

  1. #361
    Team Member hupiveneilija's Avatar
    Join Date
    Oct 2014
    Location
    Finland
    Posts
    263
    Post Thanks / Like

    Default

    Hi!
    Off the shelf, made for dellorto 40mm.

  2. #362
    Team Member
    Join Date
    Jul 2017
    Posts
    34
    Post Thanks / Like

    Default

    very interested to see if the carb stacks and slight enlargement helps much

  3. #363
    Team Member hupiveneilija's Avatar
    Join Date
    Oct 2014
    Location
    Finland
    Posts
    263
    Post Thanks / Like

    Default

    To me it seems that throttle response is better everywhere. These should be little shorter to gain more up top. But, we have had very hot here for a long time and it still goes like before on cooler days despite putting one step smaller mainjet!

    -J-

  4. #364
    BoatRacingFacts VIP
    Join Date
    Aug 2008
    Posts
    45
    Post Thanks / Like

    Default

    sorry to ask this late in the thread, but for a stock 49 ci motor, in racing, should use a 059 jet? is that sea level? also, 19 degrees tdc? thanks a lot.

  5. #365
    Team Member
    Join Date
    Mar 2017
    Location
    Central AR
    Posts
    4
    Post Thanks / Like

    Default

    PIP, we just pulled the 54D jets out of a stock 20" motor and went to install new55D jets thinking it would be an increase ,turns out I think they were drilled? A .059" machine bit fit perfectly, but 19 deg was too much and it lean stuttered on top, backed of to 17 and now it turns up 6350 with a 22 raker, for what its worth? this is on 1656 Havoc aluminum boat, 52mph

  6. #366
    BoatRacingFacts VIP
    Join Date
    Aug 2008
    Posts
    45
    Post Thanks / Like

    Default

    any idea the elevation? thanks a lot.

  7. #367
    Team Member
    Join Date
    Mar 2017
    Location
    Central AR
    Posts
    4
    Post Thanks / Like

    Default

    We are in central Arkansas, I dont know the elevation but its hot(90s) and humid now.

  8. #368
    Team Member
    Join Date
    Jul 2017
    Posts
    34
    Post Thanks / Like

    Default

    odd that it didn't like 19 deg of timing pretty sure that's what my 1992 70hp 56ci was factory, as well my 1987 70hp, I believe even the older 75hp 49ci was set at 19deg factory. Wonder if you outta run an even bigger jet and try 19 deg, maybe not idk?

  9. #369
    Team Member
    Join Date
    Mar 2017
    Location
    Central AR
    Posts
    4
    Post Thanks / Like

    Default

    Well we struggled to break past the 6000 mark until installed a jackpate, now its about as high as it can run and not blow out so we can go back to jetting and timing, like PIP said 19 seems to be the magic number?

  10. #370
    Team Member
    Join Date
    Jul 2017
    Posts
    34
    Post Thanks / Like

    Default

    If you read through past post on here you'll see the op has tried going past 19 and has had some issues, I may be wrong I think he is running 20 deg now or maybe he is back to 19. I know he tried 21 maybe 22 and chewed up a piston. Hopefully hupiveneilija chimes in on his results. Now granted he may be running 20 or 21 but he has done some port work runs a prop and low water pick up that let him raise his motor way up and is up in the rpms with his motor.

Thread Information

Users Browsing this Thread

There are currently 6 users browsing this thread. (0 members and 6 guests)

Similar Threads

  1. "Hi Johnson" - Prop Master - Story
    By Tomtall in forum Propellers
    Replies: 5
    Last Post: 06-13-2011, 05:36 AM
  2. Dennis Johnson "Trafficade" Racing
    By Ron Hill in forum Boat Racing Encyclopedia
    Replies: 1
    Last Post: 11-05-2006, 07:26 PM

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
  •