Mark 28 issues

Home Forum Ask A Member Mark 28 issues

This topic contains 31 replies, has 12 voices, and was last updated by Tubs Tubs 2 years, 8 months ago.

Viewing 15 posts - 1 through 15 (of 32 total)
  • Avatar
    wedgie

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 966
    Topics: 94
    #5470

    Just getting back to this darkside motor. I got it running a couple years ago, but suspected the crank halves are leaking, so put it aside.

    Also, as many of you know, the starter is integral to the hood, so to test run without it, you need to rope start it. When doing so, as I remember, it would often yank back on the rope half way through the pull. hard enough that it would yank the rope out of my hands. I’ve had that happen on a omc 6 horse too. Timing issue ?

    My Mercury Mark 28 has 110/112 lbs. Is that acceptable ?

    Thanks

    Avatar
    betty-ann-bernardd

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 163
    Topics: 2
    #45586

    not timing issue.
    that compression is fine.

    Avatar
    wedgie

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 966
    Topics: 94
    #45589

    Thanks Dave.

    Avatar
    20mercman
    US Member - 2 Years
    Replies: 583
    Topics: 21
    #45619

    I have quite a few of the 22 cid. power head motors, and I have yet to have one where the case halves were leaking. I have found crank seals, transfer port covers, fuel pumps, even a very loose reed block retainer bolt that can cause a crank case leak. What lead you to believe you have a case leak? These are real easy to separate the cases, so opening it up would not be much of an issue. A good time to replace the bottom crank seals anyway. As Dave said, this compression is good. Another item to check is the exhaust baffle cover to make sure it has not dried out and is leaking. Exhaust can leak into the water, and water can get into the block if they are leaking. I had a salt water motor that the baffle plate corroded through. These are great motors, and I am sure you will really like it once you get the bugs worked out.

    Steve

    Avatar
    garry-in-tampa
    Lifetime Member
    Replies: 3146
    Topics: 30
    #45629

    Jerking the rope out of your hand is the characteristic off an over advanced ignition. The start position is usually set at top dead center. Fireing before TDC gives more power at higher speeds but makes the motor want to run backwards at cranking speeds. A racing motor with a fixed timing takes a very strong arm to crank over sucessfully. . . 😆

    Avatar
    jeff-register
    US Member - 1 Year
    Replies: 1121
    Topics: 47
    #45645

    If you suspect someone else having the halves apart they may have missed the o-ring that is part of the case halves. What makes you think they are leaking? Try grounding the mag to the block. Those motors are great at reversing current with the mag. Mine was missing on the top then the bottom screwey! Bonded the mag & it ran great. Look at the points for overheating, mine turned gold they were so hot from the reverse!!

    Avatar
    wedgie

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 966
    Topics: 94
    #45651

    I’m almost positive it had been apart before I got it, so that’s why I thought it may be leaking . The p/o stripped the outside of the power head with paint remover too. I will pull the flywheel and have a look at the points again though it hadn’t had much run time on it since I replaced the coils. It’s been so long now that I don’t remember what they looked like . I must’ve cleaned them at that time but don’t recall. I have the service manual now, so I will read up on it this time around.

    I could get it to start but the rpm’s wouldn’t come up. The carb was clean and set up properly as far as I knew at the time. I have learned a few things since I did this motor so maybe if I go back in and check all the areas Mercman has listed this weekend I’ll spot something I’ve missed 😉

    So, having the throttle cranked wide open on this hard to start motor would cause it to pull back?
    Since I ruined my rotator cuff a few years back, this is an accurate depiction of my arm strength. 😆

    But once I get it started 😉 !!

    Avatar
    wedgie

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 966
    Topics: 94
    #45654

    Video from a few years ago

    http://vid635.photobucket.com/albums/uu … -00003.mp4

    Avatar
    billw
    US Member - 2 Years
    Replies: 1028
    Topics: 35
    #45661

    I start them with the top on. Once it’s warm, I take the cover off. Yes, while it’s running. Yeah, it rubs a bit but no worries. It won’t get jammed or anything.

    Avatar
    20mercman
    US Member - 2 Years
    Replies: 583
    Topics: 21
    #45663

    I was going to post this before, but my post ended up getting deleted, and I forgot to add this when I retyped it. As Jeff pointed out, there is an "O" ring that goes around one of the bottom crankcase bolts that has to be in place. This should stand proud of the face of the case in order for it to seal properly. It is something that can be easily left out if not aware of it.

    Steve

    Avatar
    jasonh

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 118
    Topics: 7
    #45686

    The crankcase on the early to mid 60s are prone to leaking. I have been through at least 7 or so 60-65 Merc 200s and they all leaked on fuel pump side where crankcase halves meet. There is a fairly long span between bolts in that area which mercury eventually changed. There is a blank (not drilled) boss on the early motors that I have thought about drilling and tapping then using.

    As far as the rope staying with mag: Yes there is a little notch in crown for knot, DONT use it! The rope knot doesn’t seem to release well with this design. I had one start and swing the big wooden handle around like a medieval ball and chain, at least it felt that way. Don’t ask how I know all this. Probably others out there who can also say they have had a beat down by one of these.

    Avatar
    20mercman
    US Member - 2 Years
    Replies: 583
    Topics: 21
    #45689
    quote JasonH:

    The crankcase on the early to mid 60s are prone to leaking. I have been through at least 7 or so 60-65 Merc 200s and they all leaked on fuel pump side where crankcase halves meet. There is a fairly long span between bolts in that area which mercury eventually changed. There is a blank (not drilled) boss on the early motors that I have thought about drilling and tapping then using.

    As far as the rope staying with mag: Yes there is a little notch in crown for knot, DONT use it! The rope knot doesn’t seem to release well with this design. I had one start and swing the big wooden handle around like a medieval ball and chain, at least it felt that way. Don’t ask how I know all this. Probably others out there who can also say they have had a beat down by one of these.

    Good information Jason! Perhaps I have been lucky with my cases. Although I rebuild all of them first, perhaps I have corrected the leak without even knowing it. As for the rope getting stuck in the notch! I almost had that happen myself. I didn’t have the wood handle on mine though! Yikes!

    Steve

    Avatar
    wedgie

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 966
    Topics: 94
    #47083

    I for some stupid reason only replaced one of the coils a few years back, so I replaced the remaining original coil and cleaned the points . It runs better now, but the case is leaking and I only have myself to blame. I must be getting oldtimers disease as I forgot that I had it apart to change the crank seals .doh 😳 ! I will take it apart and check all those things you guys have mentioned. Thanks

    http://vid61.photobucket.com/albums/h57 … s1575e.mp4

    Avatar
    wedgie

    Notice: Trying to get property of non-object in /home/aomcio5/public_html/wp-content/themes/monstroid2/bbpress/loop-single-reply.php on line 19

    Replies: 966
    Topics: 94
    #47091

    Jeff and 20mercman are right about that o ring. It must’ve been absent when I first had it apart back when. I will order a replacement and put it back together and use some gel seal on the halves this time . I anticipate a struggle getting the pistons back in. Seems like it’ll be tricky with them still attached to the crank .

    Close inspection of this little check valve welch plug shows it to be loose too. Tap it in and a little sealer of some sort ❓

    Avatar
    20mercman
    US Member - 2 Years
    Replies: 583
    Topics: 21
    #47098

    Glad you decided to take it apart and make sure. This the kind of thing that anyone of us can easily overlook. I usually put the crankshaft in on these with just my fingers. You can use a hose clamp and a couple of popsicle sticks to hold the rings down if you want to. I use STP as the stuff is slippery and it really helps sliding into the bore. I usually do the bottom cylinder first as you have less room to work in that area. You can see what you are doing much easier on top. I put the cylinder block on a bench about 2 feet off the floor, as it is easier to hold the crank from above.

    Steve

Viewing 15 posts - 1 through 15 (of 32 total)

You must be logged in to reply to this topic.