Topic: 1972 Mercury 20 hp – Page 2 – Antique Outboard Motor Club,Inc

This topic has 20 replies, 7 voices, and was last updated 3 years, 7 months ago by farmboy71.

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August 18, 2021 at 5:46 am #245059
billw
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US Member
I suppose it’s possible it could be a top or bottom seal but I’d be surprised, especially since you had the flywheel off. I would think you’d have noticed a lot of oil in the mag plate area, if the seal was bad. Speaking of that, did you torque the flywheel nut with a torque wrench, when you put it back on? The spec for that engine is pretty high, compared to an OMC. I guess this is a stupid question but you’re sure the magneto is advancing and the carb’s throttle plate is opening at least a little bit, when you move the throttle handle, right? I seem to remember some plastic and funky linkage-action going on, on those things. Something might be stuck or broken?

Long live American manufacturing!
August 18, 2021 at 8:49 am #245067
dave-bernard
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US Member
was the fly wheel 6bolts removed. I hope not . if so it may have been put back wrong.
August 18, 2021 at 9:51 am #245072
farmboy71
Participant
I did not remove the six bolts only the two it said to pull it. I am not sure about the plastic linkage if it is working right or not. I can only advance the throttle when it is in gear. Everything moves then.
August 18, 2021 at 5:00 pm #245103
billw
Participant
US Member
It should advance the throttle in neutral, at least enough to crack open the throttle plate somewhat. If the throttle plate is at dead idle and you try to start it, that might be why it just pops. I am pretty sure those had a neutral RPM limit adjustment. Maybe that’s over-adjusted…..I should get off my butt and go look at the manual…

Long live American manufacturing!
August 18, 2021 at 5:44 pm #245111
wedgie
Participant
Here’s some info

https://maxrules.com/timingindex.html
August 18, 2021 at 8:58 pm #245117
farmboy71
Participant
Thanks. I will check it out. I found part of my problem tonight. The wire that goes from one of the breaker points to the coil is broken. I had spliced it back together but now it came apart at the points. I might be able to solder it back together.
August 19, 2021 at 5:41 am #245127
billw
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US Member
First post said good spark. Now I am curious as to your method for testing spark, in the beginning….

Long live American manufacturing!
August 19, 2021 at 10:04 am #245134
outbdnut2
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US Member
How did you check for spark? Spark jumping the spark plug gap in air under no compression usually means you have good spark, but if the voltage is weak, it may not fire well under compression. You should be able to make the spark jump 1/4 to 3/8th inch in free air. (some like to see 1/2 inch). You can make a test jig to do this, or I do the next best thing, taking an old spark plug and prying the gap wide open.

Dave
August 19, 2021 at 11:32 am #245140
Mumbles
Participant
Simple variable gap spark indicators.
- This reply was modified 3 years, 8 months ago by Mumbles.
- This reply was modified 3 years, 8 months ago by Mumbles.
August 20, 2021 at 9:48 am #245214
farmboy71
Participant
I just grounded the plug and pulled to see if there was spark. Both seem nice and blue. When I was checking the top crankshaft seal the wire broke for the top cylinder. Fixed that yesterday. I got spark on both cylinders again. I will try and see if it will spark a 1/4 inch gap this evening and then hopefully try and start it again. Thanks for all of the help.
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