Logo
Page 1 of 2 12 LastLast
Results 1 to 30 of 32
  1. #1

    Default ‘97 Johnson 70 Idle issues

    Hi all, so I’m new to the whole powerboat thing. Working my way through trying to make this (New to me) 70hp more bulletproof. This engine is converted to premix, with a new fuel pump, rebuilt carbs with new gaskets, needles, floats, etc. , but I’m still having trouble getting it to idle without the throttle cracked open. Tested the compression and came out with 75psi on all three cylinders (cold). Pulled the head off and think it might be a bad head gasket? Take a look at the photos, any input is greatly appreciated! Hoping she doesn’t need new pistons/rings....

    Click Here for Photos - couldn't get the uploader to work
    Last edited by C.hillsailing; 08-09-2020 at 06:14 PM.

  2. #2
    Join Date
    May 2013
    Location
    Scarborough, ON
    Posts
    146

    Default Re: ‘97 Johnson 70 Idle issues

    You should make sure that your compression gauge is working correctly.
    Mine is 30+ years old, and last time I was using it, a tiny hole developed in the hose. Didn't know it at the time.
    I then had a good reading on one cylinder, and a low reading on the next.
    That one threw me for a tizzy until I figured out what was going on.
    Guess it's kind of late for that now.
    If it were me I think I'd Seafoam the piston rings and let it sit for an hour or two, and then Seafoam them again.
    Might be just carbon build-up on the rings?
    When it comes to outboards I'm still green, but getting better at it.
    Anyway, good luck with it and let us know what you find out.

  3. #3
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    Post some close up pictures of the cylinder walls.-----75 PSI is too low in my opinion.

  4. #4

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by CarMech1969 View Post
    You should make sure that your compression gauge is working correctly.
    Mine is 30+ years old, and last time I was using it, a tiny hole developed in the hose. Didn't know it at the time.
    I then had a good reading on one cylinder, and a low reading on the next.
    That one threw me for a tizzy until I figured out what was going on.
    Guess it's kind of late for that now.
    If it were me I think I'd Seafoam the piston rings and let it sit for an hour or two, and then Seafoam them again.
    Might be just carbon build-up on the rings?
    When it comes to outboards I'm still green, but getting better at it.
    Anyway, good luck with it and let us know what you find out.
    Thank you! Brand new compression gauge so I don’t think that’s the issue. I’ll try cleaning it out and see if that helps

  5. #5

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by racerone View Post
    Post some close up pictures of the cylinder walls.-----75 PSI is too low in my opinion.
    Will post pics tomorrow. But from initial observation they were smooth. Didn’t see any vertical scratching

  6. #6

    Default Re: ‘97 Johnson 70 Idle issues

    I’ll add that it was running great until a VRO failure, at which point I switched to premix, installed a new pump, and rebuilt the carbs.

  7. #7
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,665

    Default Re: ‘97 Johnson 70 Idle issues

    Exhaust side of pistons scuffed...
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  8. #8

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by faztbullet View Post
    Exhaust side of pistons scuffed...
    So do you think that the absence of soot there means it’s scored down the side of the piston?

    The cylinder walls don’t show any damage, should I lightly hone them anyways and replace pistons and rings regardless? Or skip honing?

    also, do you think that happened because of the vro failure?
    Last edited by C.hillsailing; 08-10-2020 at 10:58 AM.

  9. #9
    Join Date
    May 2015
    Posts
    2,327

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by C.hillsailing View Post
    So do you think that the absence of soot there means it’s scored down the side of the piston?

    The cylinder walls don’t show any damage, should I lightly hone them anyways and replace pistons and rings regardless? Or skip honing?

    also, do you think that happened because of the vro failure?
    Have you tried a different gauge? More than one has been bad even new.

  10. #10

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by flyingscott View Post
    Have you tried a different gauge? More than one has been bad even new.
    Nope, but it seems like it’s starving for fuel, so wouldn’t that relate to poor compression? Or is there something else that could make it only went to idle with a tiny bit of throttle?

  11. #11
    Join Date
    May 2015
    Posts
    2,327

    Default Re: ‘97 Johnson 70 Idle issues

    good luck with that

  12. #12

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by flyingscott View Post
    good luck with that
    Lol thank you. I just tested the gauge vs a scuba tank regulator. Seems to be accurate even though it’s cheap and Chinese
    Last edited by C.hillsailing; 08-10-2020 at 12:19 PM.

  13. #13
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    75 PSI is too low.----Sometimes it is hard to convince folks about compression values and many arguments result !!

  14. #14

    Default Re: ‘97 Johnson 70 Idle issues

    No worries! I’m just looking for advice and what could be the cause - without spending too much money on replacing things that don’t need to be. I appreciate that others are making sure I’m testing everything right.

  15. #15

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by racerone View Post
    Post some close up pictures of the cylinder walls.-----75 PSI is too low in my opinion.
    Just added a close up to the folder that’s originally linked. Let me know what you think.

    I was thinking normal wear and tear, since I can’t feel anything or get a fingernail to catch on anything. But then again, I don’t know much about engines

  16. #16
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    The picture that was added clearly shows that the motor MUST come apart for repairs.-----Damage to the piston / rings.-----Took me less than 2 seconds to decide that you are faced with that kind of repair work.

  17. #17

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by racerone View Post
    The picture that was added clearly shows that the motor MUST come apart for repairs.-----Damage to the piston / rings.-----Took me less than 2 seconds to decide that you are faced with that kind of repair work.
    Copy that, sounds like I’m ordering parts. Will the standard size be good as far as pistons & rings? Or do the cylinders need to be bored out?

  18. #18
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    You can not determine what needs to be done until you have it apart and inspected.----Post pictures of the pistons when you have it apart.

  19. #19

    Default Re: ‘97 Johnson 70 Idle issues

    Will do, thank you for the help

  20. #20

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by racerone View Post
    You can not determine what needs to be done until you have it apart and inspected.----Post pictures of the pistons when you have it apart.
    Okay, got her apart. Photos are in the folder linked above.
    The really bad piston is the top cylinder. Then the middle and bottom both look similar. Look bad, but feel smooth.

    As far as the cylinders, the top cylinder definitely has some texture. Then the middle and lower are mostly smooth. I can barely feel anything on those.

    Let me know what you think as far as what needs work. Obviously new rings and at least one piston, and probably a bored out top cylinder. But I’m just guessing

  21. #21
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    Now do you agree with post #3 ----??//

  22. #22

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by racerone View Post
    Now do you agree with post #3 ----??//
    I’m not quite sure what you mean. I don’t remember disagreeing? The scratches were found behind the exhaust and intake ports where you can’t see without disassembly.

    I’m asking questions because I’m trying to learn. I thought this was a good forum because usually people are polite. I have posted pictures of everything you wanted, I am purely just trying to learn as much as possible and make sure that I’m not spending too much money. I’m sorry if that came off as skepticism in my responses.
    Last edited by C.hillsailing; 08-14-2020 at 09:09 PM.

  23. #23
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    Post # 1 tells me you were hoping with a few new carburetor parts / new fuel pump that the motor should run nicely again.-----And read post #5 again !----Sorry ---but there are many folks who doubt solid advice based on years of experience !

  24. #24

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by racerone View Post
    Post # 1 tells me you were hoping with a few new carburetor parts / new fuel pump that the motor should run nicely again.-----And read post #5 again !----Sorry ---but there are many folks who doubt solid advice based on years of experience !
    Post #1 pretty clearly tells you what I already did - so you know what to rule out so we can hopefully find the issue.

    Post #5 is just my honest observation. I’m telling you what I can feel because you can’t feel it yourself. I thought that sort of insight would be helpful.

    I think you are reading into my posts a little too much, which lead to these non-productive assumptions. Relax a bit man. I have said several times in this thread that I’m new to this and I don’t know what is or isn’t salvageable. Just looking for someone to tell me what to replace. I have done and posted pictures of everything you’ve asked. Obviously I’m not doubting you...

  25. #25
    Join Date
    May 2015
    Posts
    2,327

    Default Re: ‘97 Johnson 70 Idle issues

    Clean the top of the piston off and look to see if it has been bored already. Should be a part # on there and possibly a size.

  26. #26

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by flyingscott View Post
    Clean the top of the piston off and look to see if it has been bored already. Should be a part # on there and possibly a size.
    oh good point, luckily I have a pic that shows the number - it’s an original standard size piston

  27. #27
    Join Date
    May 2015
    Posts
    2,327

    Default Re: ‘97 Johnson 70 Idle issues

    Quote Originally Posted by C.hillsailing View Post
    oh good point, luckily I have a pic that shows the number - it’s an original standard size piston
    The block will probably need to be bored at least .020 over. Take the block to the machine shop and see how far it needs to be bored. I would look for a WSM kit thats what I used for my 92 model. I think I got it for less than $500.

  28. #28
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,665

    Default Re: ‘97 Johnson 70 Idle issues

    Motor needs bored, all 3 cylinders and needs exhaust bridge mod....see post #7. WSM is best kit and make sure you replace 3 vane impeller even 2 years
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  29. #29
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    Most 97 models already had the 6 vane impeller.-------And there are still folks out there who think you can run an outboard motor with no cooling water to the impeller.------Found 2 motors 70 HP with that issue a few weeks ago.----And another 30 HP with a melted impeller housing the other day.

  30. #30
    Join Date
    Sep 2010
    Posts
    20,309

    Default Re: ‘97 Johnson 70 Idle issues

    Most 97 models had the 3 vane impeller shown in the parts books.----Should have had a 6 vane impeller installed years ago.---------And there are still folks out there who think you can run an outboard motor with no cooling water to the impeller.------Found 2 motors 70 HP with that issue a few weeks ago.----And another 30 HP with a melted impeller housing the other day.

Page 1 of 2 12 LastLast

Similar Threads

  1. 2000 Johnson 115 low throttle idle issues
    By WinnipegMike in forum Johnson Evinrude Outboard Forum
    Replies: 6
    Last Post: 08-03-2020, 08:59 PM
  2. 60 hp johnson idle issues
    By Breezy06 in forum Johnson Evinrude Outboard Forum
    Replies: 2
    Last Post: 04-11-2020, 11:33 PM
  3. 04 Johnson 115 idle/running issues
    By Evilrude in forum Johnson Evinrude Outboard Forum
    Replies: 2
    Last Post: 05-16-2017, 08:18 PM
  4. 76 johnson 115hp v 4 idle issues
    By jrupp in forum Johnson Evinrude Outboard Forum
    Replies: 5
    Last Post: 07-13-2016, 02:22 PM
  5. 2000 150 HP Johnson Ocean Runner Idle Issues Please help
    By cmone42 in forum Johnson Evinrude Outboard Archive
    Replies: 3
    Last Post: 06-11-2009, 12:30 PM

Posting Permissions

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