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  1. K

    1981 Mercury 7.5 2 stroke

    Double post error.
  2. K

    1981 Mercury 7.5 2 stroke

    An update: Running good. Easy start, accelerating well and idles nicely. Seating rings here now. It’s below freezing here today. That’s not smoke you’re seeing.
  3. K

    1981 Mercury 7.5 2 stroke

    That’s an interesting place to illustrate the o-ring in the parts book. The adjacent felt washer is shown with the crankshaft. Hope my o-ring is close. Lol. The powerhead is not coming off again at this time. Thanks for pointing that out @racerone. Interesting how it is designed to lube the...
  4. K

    1981 Mercury 7.5 2 stroke

    I visited the local Mercury Marine dealer today. I spoke to a technician. I asked him about the air leak out the end of the crankshaft. Also the o-ring situation on the driveshaft. He recalled this. He said for whatever reason, whoever was making cranks for these engines back in the day, they...
  5. K

    1981 Mercury 7.5 2 stroke

    Removed the motor again. I dug through my shop supplies. Found an o-ring that fits. Installed it on the driveshaft. There is a groove in the shaft to retain it.
  6. K

    1981 Mercury 7.5 2 stroke

    I’m not ignoring you @racerone. You have provided some valuable info. I’m not sure what info I am to glean from your post #40. Starting a paragraph with a bunch of question marks is interesting. I suppose I am to try and read between the lines and guess what you are attempting to say. You state...
  7. K

    1981 Mercury 7.5 2 stroke

    I spent some time researching the air coming out the end of the crankshaft. I studied the parts and technical book and a few other similar models. Nothing confirmed my inquiry. I sprayed soap in there and pressurized it to maybe see where the air was coming from. Inconclusive. I tried applying...
  8. K

    Motor Won't Turn Over

    The engine is turning over. The flywheel and crank are turning. Its not seized. “Won’t turn over” generally means the engine is seized. Your engine is not seized. It just wont stay running. I assume this is a fuel injected 4 stroke?
  9. K

    1981 Mercury 7.5 2 stroke

    I’ll take a closer look in there later this evening. Looking at the Mercury parts web site, they only show a felt washer in there. I do have that. Its in place. #4 in the image below. #2 is the lower crank seal. My engine does not utilize #3, some type of spline adaptor. Perhaps a little...
  10. K

    1981 Mercury 7.5 2 stroke

    Leaking air out center area here.
  11. K

    1981 Mercury 7.5 2 stroke

    Leak down test shows the new intake port inspection cover leaking. Tightened it again still leaks a small amount. I’ll remove the gasket and spray some Permatex Copper Gasket aerosol on both sides. Reinstall install it again. Minor issue but might as well do up right. Another interesting...
  12. K

    1981 Mercury 7.5 2 stroke

    MHeating from crank bearing housing worked perfectly. Thx. I completed powerhead reassembly yesterday. Today I’m sourcing some material to make the exhaust block-off plate. I’ll pressurize the assembly and monitor for possible leak down. I noticed less sprung piston ring movement when...
  13. K

    1981 Mercury 7.5 2 stroke

    I have a couple questions: The small holes in the tops of the pistons. Are they possible lube holes to piston pin? I’m doubtful but want to be sure. I can’t seem to spray aerosol lube down thru them. Next Q. What’s suggested method to get the upper main crank bearing out of the housing? A...
  14. K

    1981 Mercury 7.5 2 stroke

    @racerone earlier mentioned changing the upper water tube plastic washer. I was wondering where this was. Found it. Thank you!
  15. K

    1981 Mercury 7.5 2 stroke

    My local marine dealer had everything I needed stock. I’m impressed. Clean up time and reassembly next.
  16. K

    1981 Mercury 7.5 2 stroke

    I removed and tore down my 7.5 tonight. These things are so simple. Easy to work on. The whole experience was a pleasant. One of the easiest engines I’ve ever pulled and opened up. The cylinder walls look great. No scoring seen. Some mild scoring on the rings. The crank seals were pretty...
  17. K

    1981 Mercury 7.5 2 stroke

    The rings are sprung. I’m not convinced they are stuck. I see enough scoring on the rings to lead to low compression numbers. Ideally I’d like to get full power from this engine. It’ll be going on a 10 ½ foot SIB. It won’t be mainly trolling around fishing. This project is my first time digging...
  18. K

    1981 Mercury 7.5 2 stroke

  19. K

    1981 Mercury 7.5 2 stroke

    Reporting back. Removed bypass access cover. All rings are still sprung. None broken. I see fine scoring patterns on the rings. They look pretty worn to me. I’ve limited experience with this. I attempted to take a few photos. Difficult to get clarity with cell phone camera. Hone and ring time?
  20. K

    1981 Mercury 7.5 2 stroke

    Will do. Thx. Any chance that piston ring end gap would be measurable from that by pass cover? I suspect no, that end gap pins will be 90 from the ports. I will inspect rings and test them for spring tension.
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