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M60 Timing

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MarinerScott

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Hello All,

I have a 1984 Mariner M60 three cylinder. I believe the timing is off after pulling the flywheel for a rebuild. The Seloc book does give me a max advance of 23 degrees at full speed. What should I have at idle, say 600 RPM? Nothing listed in the book. It is hard to start and does back fire if it doesn't start and as it comes to rest after letting off the starter. Suggestions?

Thank you,
MarinerScott
 
The spark has to be retarded to idle the motor down, the only way it can be done. (Running on maximum spark advance only, my boat maintains 20 plus mph.) So, IF the motor is timed correctly, then that is not your problem.

I run a similar motor and have had problems like you. In my case it's the carbs. (I assume you have the carbs that are through bolted to the block from the front.) This carb is easy to work on, but has a problem with idle circuit plugging (that's driving me nuts!) A tiny passage from the bottom of the fuel bowl--where any crud collects--leads upward to the idle mixture screw and is easy to plug up. This creates bogging, backfiring, hard starting, and bad temper in me! The fix is to pull the carbs off, drop the fuel bowls, and clean out those passages thoroughly.

But first, try opening out the idle mixture screws CCW abouit 1/4 of a turn and see if that helps.

Jeff

PS: I'm working on a fix for these carbs and will post my findings here.
 
Last edited:
fastjeff, thank you for the quick reply. I rebuilt the carbs as part of the engine rebuild. They were clean/rebuilt anyway. The idle circuit is OK. 1-3/4 turns out per book and adjustments do adjust idle.


I started the engine after rebuild (new pistons/bore) and the idle advance was after TDC by a few degrees. That justr did not seem right. I advance to 3 degrees BTDC and seems better. Since new rebuild I cannot run at full throttle. Still in the driveway. I'm down to four items;

Timing Advance
25 to 1 break in gas
Compression
Just need more time to seat rings

Thoughts?
 
That motor is VERY sensitive to idle adjustments. The only way I can get them right is with an infrared temp gun: I shoot the body of each spark plug and adjust the idle mixtures until they are all the same (about 105 ' F).

If you simply dialed them in at 1 3/4 turns, THAT is your problem.

Jeff
 
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