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  1. M

    mercruiser 140 will not exceed 4000rpm

    Ya, a little vague. My bad. Failure was due to timing gear missing a few teeth. Was replaced and new valves, head and block planned, gaskets all around. Compression strong at 154 for all four. When I checked the timing it was bang on what it should be but i'm having a block on what that is...
  2. M

    mercruiser 140 will not exceed 4000rpm

    Morning all! So my newly rebuilt 1984 140 will not go past 4000 rpm and 29-30 mph. Prior to having the engine failure I was able to hit 4400-4600 and 37-39mph. It also seems to be missing "power" between 3000 and 4000rpm. Takes longer than I would call normal to get there. Engine runs good...
  3. M

    Engine cut out while slowing down....

    So final chapter closed. Had the guy tear it down. Result was several teeth broken/stripped off the timing gear. Three of the valves were not lapped properly in the head. Replaced & fixed what wasn't working, changed the rings (pistons and walls were beautiful). She purrs like a kitten now...
  4. M

    Engine cut out while slowing down....

    Hey guys. Just wanted to give an update. Machine shop I was working with quoted me WAY too high for a tear down & rebuild. Unfortunately I'm at a point that exceeds my ability & comfort level. Found a place not too far away that will help me out! Dropping the whole boat off later today. He...
  5. M

    Engine cut out while slowing down....

    Yup. done at TDC.
  6. M

    Engine cut out while slowing down....

    Definitely no holes in the piston. Unless they are microscopic.
  7. M

    Engine cut out while slowing down....

    Just for clarification. It's not running. It hasn't run since it died back in August. Then I had the head redone.
  8. M

    Engine cut out while slowing down....

    Ok. So managed to rig together a few adapters to pressurize each cylinder. I hear air escaping into the block. I assume that points towards rings?
  9. M

    Engine cut out while slowing down....

    How do I use a compressor to introduce air? Would this be at WOT?
  10. M

    Engine cut out while slowing down....

    Another question. During compression test, should the throttle be wide open? If so, why?
  11. M

    Engine cut out while slowing down....

    Phew! Thanks for the confirmation! OK. Bare with me. Measure literally from bottom of the spring to top? I assume I should do this at TDC to ensure they are closed?
  12. M

    Engine cut out while slowing down....

    Ok. I used manual 3. Page 6A-1 says 93 Page 6B-1 says 130 Stupid question. Which engine do I have? 1984 Mercruiser 140 s/n 6777639
  13. M

    Engine cut out while slowing down....

    My bad. I did a wet compression test. I did NOT do a leak down test. I have not been able to start the engine, it's still in indoor storage in the garage. When I installed the head I followed the manual. Torqued down to 93ft/lb. My piston walls are really nice. No scoring or marks what so...
  14. M

    Engine cut out while slowing down....

    Reminder, this is with the rebuilt head already.
  15. M

    Engine cut out while slowing down....

    OK. New gauge. Consistent results: 1 - 105 2 - 75 3 - 60 4 - 60 Did leak down with no change. Rebuild time? :-(
  16. M

    Engine cut out while slowing down....

    So readjusted the rockers as per the proper lash setting (up & down). Did a compression test. I'm now thinking my gauge is inaccurate. Without changing anything, I got different readings from the same cylinder 5 minutes apart. 50 psi difference. Picking up a new gauge tomorrow to confirm.
  17. M

    Engine cut out while slowing down....

    Yup. Following manual I did the spin test. I'll redo today using vertical movement. I did a quick test again last night backing off an 1/8 turn on one and pressure went from 40 to 100. Fingers crossed it is something as silly as that!
  18. M

    Engine cut out while slowing down....

    Interesting. I followed the manual to adjust the rockers. 3/4 turn after lash was eliminated. Should I have run the engine for a few minutes before testing compression? It has not been turned over since late August 2020. Maybe I should try backing off the rocker nut an 1/8-1/4 turn to...
  19. M

    Engine cut out while slowing down....

    OK. So finally got the head put back on! Did a compression test: 1 - 45 2 - 65 3 - 65 4 - 75 When my problem happened originally I had 1 - 40 2 - 0 3 - 0 4 - 40 Am I looking at a combination of I had a blown head gasket, valves not sealing correctly and now piston ring issues? I was hopeful...
  20. M

    Form a gasket instead?

    Hey guys. Can I use form a gasket or RTV instead of the Mercruiser gasket for this one location? Replacing #29
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