Logo
Get instant online access to repair manuals for your Mercury / Mariner outboard. Online Manuals
MercuryMariner
Order printed Mercury / Mariner service manuals — shipped to your door! Printed Manuals
MercuryMariner
Use engine diagrams to find & order parts for your Mercury / Mariner engine. Engine Diagrams
MercuryMariner
Find parts quickly with Mercury application guides. Quick Parts Guide
MercurySierraCDI
Results 1 to 11 of 11
  1. #1

    Default What is the effect of the flywheel being in the wrong position?

    I recently replaced the stator, trigger assembly and flywheel on my 1986 Mercury 75HP. It's a project motor that had some mysterious and intermittent no-spark occurrances. So I threw as many ignition parts at it as I had on hand.

    Motor ran smoothly before I swapped the parts, with a nice steady idle. But since the swap it runs like crap. Super-high idle that I cannot bring down, and it's running extremely lean. I fear I may have re-installed the flywheel incorrectly. I admit not paying attention to the "compass" position of the flywheel when I pulled the old one off and put the new one one. I just set it back down on the splines, thinking it didn't matter where the magnets are.

    I now know that the position matters for timing reasons, but "IF" the flywheel is off by a little or a lot, what would the effect on the motor be?

    Feel free to call me out for being naive about the flywheel. Deserve it totally.

  2. #2
    Join Date
    Sep 2010
    Posts
    20,294

    Default Re: What is the effect of the flywheel being in the wrong position?

    If it was a splined crankshaft then there is one tooth that is missing.----You can not install the replacement in the wrong position.-----Unless of course you did not look and used brute force !

  3. #3
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,661

    Default Re: What is the effect of the flywheel being in the wrong position?

    Outer magnets position do not matter......
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  4. #4

    Default Re: What is the effect of the flywheel being in the wrong position?

    Quote Originally Posted by racerone View Post
    Unless of course you did not look and used brute force !
    I definitely did not look, just plunked it down on the splines. I was happy that it wasn't the shaft/key situation, so I just put the flywheel on any old way. Yes, rookie move, but that's what I did. I'll pull it off in the coming days and double check, but my original question stands: how would the motor behave if the flywheel was not replaced in the exact same? Any differently? Thanks.

  5. #5
    Join Date
    Sep 2010
    Posts
    20,294

    Default Re: What is the effect of the flywheel being in the wrong position?

    I believe there are magnets on the hub of the flywheel.------Those have to do with timing of the spark.-----No doubt you know what that means !

  6. #6
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    16,927

    Default Re: What is the effect of the flywheel being in the wrong position?

    If that's the motor I'm thinking of, the flywheel is attached to the hub by 8 bolts. The outer portion can be off if someone repositioned it incorrectly. If so, when attempting to time it the WOT set point will be off a mile.

    Jeff

  7. #7

    Default Re: What is the effect of the flywheel being in the wrong position?

    Quote Originally Posted by fastjeff View Post
    If that's the motor I'm thinking of, the flywheel is attached to the hub by 8 bolts.
    I never touched the bolts or took the flywheel apart, just lifted the whole thing off with a puller. My thought is that I replaced the flywheel with no consideration to it's position. And I was wondering what the effect on the running motor would be if the replaced position was off, even by a few degrees. Or would it even start?

  8. #8
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,661

    Default Re: What is the effect of the flywheel being in the wrong position?

    You really cant install the center hub wrong unless you force it ..then flywheel would be wobbly. The outer ring can be installed wrong but only thing is timing decal will be off. A motor will start and run even if a could of degrees off. Running lean will make em idle high. Make sure you didn't break the throttle slide arm on front of block as it can hold carbs open..
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  9. #9
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    16,927

    Default Re: What is the effect of the flywheel being in the wrong position?

    ..."I never touched the bolts or took the flywheel apart, just lifted the whole thing off with a puller."

    I meant someone else might have.

    Jeff

    PS: Started a triple up backwards once--it backfired, started rotating the wrong way and kept running! So much for the flywheel having to be in the "right" location.

  10. #10

    Default Re: What is the effect of the flywheel being in the wrong position?

    **UPDATE** I pulled the flywheel and sure enough, I had re-installed it incorrectly. I remember now that when I put it on a couple of weeks ago, I just sat the flywheel down on the splines, got the nut started, and hit it with an impact wrench. Yes, I'm an idiot.

    But after I replaced the flywheel correctly, it started first pop and now runs nicely and idles properly. The lesson I learned: Guess what? It matters how the flywheel is oriented!

    And in case you're wondering, this is what the shaft splines look like when you force a flywheel down in the wrong position. Lovely.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	fly3.jpg 
Views:	10 
Size:	80.0 KB 
ID:	22643  

  11. #11
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    16,927

    Default Re: What is the effect of the flywheel being in the wrong position?

    Ouch!

    Jeff

Similar Threads

  1. Replies: 1
    Last Post: 09-29-2017, 10:14 AM
  2. Wrong Flywheel?
    By geezer1 in forum Johnson Evinrude Outboard Forum
    Replies: 1
    Last Post: 02-06-2014, 04:38 PM
  3. HELP! Removed flywheel from 50hp (1983, inline 4) without marking position
    By jaykmar in forum Mercury Mariner Outboard Forum
    Replies: 4
    Last Post: 05-19-2011, 08:14 PM
  4. 1970 johnson 33hp neutral is in wrong position
    By waterdan in forum Johnson Evinrude Outboard Archive
    Replies: 1
    Last Post: 07-31-2008, 07:44 AM
  5. Flywheel installation position
    By berkleytaylor in forum Mercury Mariner Outboard Archive
    Replies: 2
    Last Post: 09-18-2006, 05:39 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
  •