Thread: Johnson "70mod"

  1. #201
    Banned
    Join Date
    Nov 2016
    Posts
    378
    Post Thanks / Like

    Default

    ok on my 1995 oval port cyl head ( omc part no 339221) the pocket depth from standard is 13.5 mm..... SST60 spec is minimum 11.176mm.


    depth of thermostat hole on oval port head is 6mm. and thickness at bottom hole on cyl head is also 6mm. (photo to show bottom hole.)

    so for me to have sst60 spec i need to shave off 2.324mm... this would still leave me with 3.676mm of metal at thermostat.



    Also I just noticed on the front of the head just above no2 plug and under the omc M is a letter L on the casting, it sticks up a touch so is there from new.


    .
    Attached Images Attached Images   

  2. #202
    Team Member hupiveneilija's Avatar
    Join Date
    Oct 2014
    Location
    Finland
    Posts
    297
    Post Thanks / Like

    Default

    Quote Originally Posted by filthy phill View Post
    ok on my 1995 oval port cyl head ( omc part no 339221) the pocket depth from standard is 13.5 mm..... SST60 spec is minimum 11.176mm.


    depth of thermostat hole on oval port head is 6mm. and thickness at bottom hole on cyl head is also 6mm. (photo to show bottom hole.)

    so for me to have sst60 spec i need to shave off 2.324mm... this would still leave me with 3.676mm of metal at thermostat.



    Also I just noticed on the front of the head just above no2 plug and under the omc M is a letter L on the casting, it sticks up a touch so is there from new.


    .
    Thank You. It needs to be ovalport head to make it sst60 specs.

  3. #203
    Banned
    Join Date
    Nov 2016
    Posts
    378
    Post Thanks / Like

    Default

    I dont know about that, because people were making their engines to same spec as sst60 before oval port engine was made ?
    oval port did not come until 1993 in most parts of the world.

    the oval port head for the 60hp and 70hp is the same part number,
    the 50hp 3 cyl oval port is not the same number and is lower compression, I dont know the thickness of the 50hp head or depth of pocket...


    on the thin cylinder head why not fill the bottom of the pocket to get correct depth ? then plug hole can then be re-taped and tiny bit machined from outside to
    give correct depth for the spark plug.
    this would save shaving the head too much by just adding a small amount of alloy in the pocket ?
    maybe this is a bad Idea ? but if it can be done then it could be a simple solution to use any of the cyl heads .
    for example have 2mm material put in the pock then just tiny shave and its perfect ?

    all depends how easy to get thicker head ?

    its just an idea that maybe could work I dont know ?
    .

  4. #204
    Team Member hupiveneilija's Avatar
    Join Date
    Oct 2014
    Location
    Finland
    Posts
    297
    Post Thanks / Like

    Default

    Hello all!

    Our midsummer, 30 minutes to midnight almost full daylight.

    Go for a boat ride or not, too many beers!
    Enjoy, I do😎
    Attached Images Attached Images  

  5. #205
    Banned
    Join Date
    Nov 2016
    Posts
    378
    Post Thanks / Like

    Default

    Looks like you have a very bright night there, here it was like that until 10.30 pm.

    beers and boats are not too good an idea when getting dark, too hard to find the little green bottles ha ha .

    best go in proper daylight for testing.

  6. #206
    Team Member hupiveneilija's Avatar
    Join Date
    Oct 2014
    Location
    Finland
    Posts
    297
    Post Thanks / Like

    Default

    Have anyone made this mod?
    Attached Images Attached Images  

  7. #207
    Banned
    Join Date
    Nov 2016
    Posts
    378
    Post Thanks / Like

    Default

    what mod ?

  8. #208
    Team Member Hevi Kevi's Avatar
    Join Date
    Jul 2013
    Posts
    25
    Post Thanks / Like

    Default

    Quote Originally Posted by hupiveneilija View Post
    Have anyone made this mod?
    Yup
    Critchfield 15" 56ci OMC
    RapidCraft Cyclone 15" 56ci OMC


  9. #209
    Team Member LittleCharger's Avatar
    Join Date
    Mar 2011
    Location
    London,ON,Canada
    Posts
    174
    Post Thanks / Like

    Default

    Quote Originally Posted by Hevi Kevi View Post
    Yup
    yup

  10. #210
    Banned
    Join Date
    Nov 2016
    Posts
    378
    Post Thanks / Like

    Default

    so come on what is the mod ?

    surely not trying the adjustable main jet ?

Thread Information

Users Browsing this Thread

There are currently 7 users browsing this thread. (0 members and 7 guests)

Similar Threads

  1. "Hi Johnson" - Prop Master - Story
    By Tomtall in forum Propellers
    Replies: 6
    Last Post: 08-09-2015, 01:27 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
  •