Poor Idling 35 hp Merc

[jslu]

1987 35 Hp Merc SN # 0B177575

My basic problem is that the motor does not operate reliability when shifting into gear while testing in a very large barrel of water. It mostly stalls.
Here is what I have done so far;

All replacement parts I have used are either new or known to be good from another properly operating motor of mine.
To date I have replaced:
Carbureator, fuel lines, fuel bulb, fuel pump and filter, switch box, stator and trigger, Ignition wires, ignition coils and spark plugs.

I have done a linc and sync per lenghty instructions on this forum which has worked successfully on other unwanted 35 HP Mercs which I buy locally for cheap money and resell. My gain is mostly the "tinkering experience", the hours I tinker are not so much important and I like to feel good to know that someone is getting a pretty good motor at a reasonable price.

To begin with, the motor really runs poorly if I set the initial timing @ 3 degrees BTDC per the instructions. It idles rough even in neutral with this timing set up and shifting to forward guaranteers a stall. Carb low speed adjusting incrementally to richer does not fix this problem. So, I ruled out a parts problem and idle speed and carb adjust as the culprit, I then began to dicker with the initial timing. I just kept advancing the timing until I noticed a smoother running engine in neutral, then I rechecked the initial timing. It was now 13 degrees BTDC! With this setting I can now shift into gear and avoid a stall if I advance the throttle quickly. I know this is not right because the 1989 35 HP Merc I have on my boat is a sweet shifter. After a brief warm up, I can shift into either gear and it doesn't care.

Right now I'm thinking bad reed valves or lower crank seal. How do you check them? I'm open to any and all suggestions and questions. The timing thing has really got me puzzled. I even checked the timing marks on the flywheel with another flywheel to rule out the remote possibility that the were incorrectly stamped at initial fabrication. They were not!

John

 

[racerone]

Maximum timing advance is set at full throttle only.-------The confusing thing for most folks is idle timing.--------Idle timing is ----THROTTLE PICK-UP TIMING and it is the point where the throttle begins to open.---Therefor idle timing is a carburetor linkage adjustment and not a timing adjustment.

 

[jslu]

racerone;

I agree 100% with your reply.
The timing sequence I was referring to at 3 degrees BTDC and then later at 13 degrres BTDC
was indeed my THROTTLE PICK-UP timing. My maximum full throttle timing is set at 21 degrees BTDC.
I also neglected to state previoiusly that a compression check of each cylinder is around 140 PSI.


John