1968 4 cyclinder Merc timing and points gap

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aliveankiken

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Not sure if my boat has a 120/140 but it is a 1968 4 cyclinder. How can I tell the difference? it idles a bit rough and has a slite miss at higher RPM's. Can anyone tell me what the points gap should be set at and were is a good place to start with the timing? Thanks
 
Volphin

Volphin

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Re: 1968 4 cyclinder Merc timing and points gap

Sounds like a 120... found some specs for you. Invest in a dwell meter to dial it in just right.

For serial number 3825578 and below point gap is 0.022" and dwell is 28-34 degrees. Timing is 6 degrees BTDC. Target idle is 500-600 RPM

For serial number 3825578 and above, point gap is 0.022" and dwell is 28-34 degrees. Timing is 6 degrees BTDC. Target idle is 650-700 RPM

HTH

V
 
Don S

Don S

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Re: 1968 4 cyclinder Merc timing and points gap

Kind of easy for the 68, the 140 didn't appear until 69.
The 140's have a harmonic balancer, the 120's have only a pulley on the crankshaft.

Before you do your tuneup, do a compression test like this. http://www.boatfix.com/merc/Bullet/97/97_25.pdf

If you have poor compression, no amount of tuning up will make it run smooth.

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aliveankiken

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Re: 1968 4 cyclinder Merc timing and points gap

Perfect, thanks for the quick answeres. Compression check great idea!!! I'll start there and move on to tune up. If all goes well me and my Son should be fishing in a couple hours. Thanks again
 
Volphin

Volphin

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Re: 1968 4 cyclinder Merc timing and points gap

aliveankiken said:
Perfect, thanks for the quick answeres. Compression check great idea!!! I'll start there and move on to tune up. If all goes well me and my Son should be fishing in a couple hours. Thanks again
Click to expand...

And THAT is priceless... I love fishing with my sons. Hope you guys have fun!

V
 
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