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Help with 1962 Merc 700 idling/running smooth

S

Sandals512

New member
Hello all,

Overall new to outboard and 2 strokes.

So, picked up a 1962 Merc 700 a few weeks back, and is in rougher shape than I originally thought.

So far here's what I've done

- Rebuilt the 3 carbs
- Rebuilt the 2 fuel pumps
- replaced 90% of the wiring
- replaced Plug wires (rodent damage)
- new Plugs
- replaced water pump impeller and gaskets
- cleaned lower unit and replaced all seals

So, I can get it started, and will accelerate and shift correctly.
Problem is just getting it to just idle.

To get it to start I have to pull up the cold start lever, give it choke and it will start fairly decently. But I can't put the cold start lever down. If I do it just dies out on me.

I've been able to do a quick throttle forward and slam.that lever down and I can give it throttle and it responds well, but if I throttle down to idle / neutral it just dies on me.

My 2 stroke knowledge is minimal.
I've played with the idle mixture to no real avail. With the timing stops as well, but I had to adjust it so far in from where it was it doesnt seem at all correct to stay there, and I cant put the cold start lever back down if I do.

Open to all auggestions.
 
fastjeff said:
Have you run a compression test? A bad cylinder or 6 will cause this.

Jeff
Click to expand...

Just ran a compression test
1 - 95
2 - 90
3 - 80
4 - 95
5 - 100
6 - 100

So #3 is a bit lower than the rest, but I don't think enough for it to be total ****.

I did just find the dist cap had a crack in it. I think the one I bought off of Ebay should get in today, so I'll swap that and see. Along with checking the timing and points (wish me luck, I've watched others set points, but never done it myself)
 
I read that on other motors that good compression is around 130; my new '92 Merc 40 4 cylinder had 140; and read where the differences should not exceed 30% - I can't count so I don't know what that means. Maybe you can find what your compression should be.
Hope your dist cap is the issue.

My Merc 40 is suffering the same idle issue; I plan on removing the carbs and cleaning them.
 
Remove the wee bypass cover to look at piston / rings on # 3-----You have to split the distributor to clean / set the breaker points too.-----Careful with the plastic parts as they can be big $$ items.
 
Well with 30% difference a motor may run.----But not run very well.-----I won't elaborate but on a 2 stroke 30% difference will spell ---DISASTER ----after a while.
 
Thanks racerone!!
I got that 30% from the 2nd video in my last post but that was for a car engine; the first video on a 4 stroke outboard mentioned the 10% difference.
With low compression, how does that do more damage to a 2 stroke engine?
 
It has to do with the amount of air pull through the motor.------After all , that air has the gasoline and the OIL to lubricate the motor !!!
 
Lights went on. The amount of air is what has the fuel/lubricant in it; hence, low compression, low air, low lubricant - 2 stroke damage.
 
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