Hard Starting 1988 115hp Mercury Inline 6

[mmccurry]

Guy's,

My Inline 6 used to start-up perfectly but 4 weeks ago it has gotten very difficult to start when cold. I've disassembled and cleaned the carbs, checked voltage on the batteries, installed a water/ fuel separator, verified enricher valve is working, replaced the spark plugs, and I'm still having problems. Once it starts the motor runs fine and restarts instantly with no problem.

I checked the spark while cranking with the old plugs and found that I only had spark on cylinders 2-4-6....nothing on 1-3-5. Thinking the problem could be related to low batter voltage and/or spark plugs I charged the battery and installed new spark plugs. The next day the engine fired up immediately from a cold start and ran smoother than it has in a long time. I immediately checked the spark in all cylinders while the engine was running and all cylinders we getting good strong spark.

Now less than a week later the engine is back to it's old habits.... very hard starting when cold.

Right now I suspect that the power pack is failing intermittently? Would the engine eventually start on only 3 cylinders? What do you guy's suggest I do next?

Thanks for any advice

 

[Laddies]

Re: Hard Starting 1988 115hp Mercury Inline 6

You have one side of the ign working, when the engine has spark on only 3 cyls. remove the red and red/white wires from the switch boxes and swap to the other box the same with the blue and blue/white wires the ck for spark if it stays on the same cyls it's a bad switch box if it moves with the wires it's a bad stator

 

[mmccurry]

Re: Hard Starting 1988 115hp Mercury Inline 6

Thanks, I'll try that.....

Is it normal for these components to fail intermittently? Would the engine eventually start with only 3 cylinders firing? Would the component work when the engine is running and not work when it is cranking?

Just trying to understand how the system works (and typically fails)

I'll make the checks you suggest and reply

 

[Laddies]

Re: Hard Starting 1988 115hp Mercury Inline 6

The stator has 2 sides that produce electricity a high and low speed winding for each of the the switchboxes 1 set of windings for each switch box, the boxes act as a dist. firing the coils and the trigger is 3 windings that tell the boxes when to fire and control the timing

 

[mmccurry]

Re: Hard Starting 1988 115hp Mercury Inline 6

I'm getting closer to solving this riddle with some interesting test results....

When I switched the blue and blue/white wire and the red and red/white wire the problem changed to the other cylinders 2-4-6 rather than 1-3-5. No spark when cranking.....however, I was able to start the engine with spark to only 3 cylinders and once the engine started I suddenly got spark on all 6 cylinders.......

It certainly matches the symptoms since the motor is very hard to start but runs okay once it is started....Why would the stator work when the engine is running but not work when the engine is cranking? Any advice would be appreciated......Unless someone has a suggestion, my next step is to go ahead and replace the stator.

Thanks

 

[j_martin]

Re: Hard Starting 1988 115hp Mercury Inline 6

I think I'd double check all the grounds before I put in a stator, especially if there's 2 ground wires coming off the stator.

Otherwise, sounds like yer doggin' it well.

hope it helps
John

 

[mmccurry]

Re: Hard Starting 1988 115hp Mercury Inline 6

Does anybody know where the stator is grounded to?

 

[Laddies]

Re: Hard Starting 1988 115hp Mercury Inline 6

On a inline 6 there is none

 

[MercFan]

Re: Hard Starting 1988 115hp Mercury Inline 6

I did find that if your stator's core cannot earth on the chassis that it can play up with the electrics a bit. We pulled the flywheel, removed the stator, cleaned the paint off the block with sand paper, also sand papered those bits on the stator core a bit and just reassembled. It didn't make any difference to start-up behaviour though.

 

[mmccurry]

Re: Hard Starting 1988 115hp Mercury Inline 6

Okay...I replaced the old stator with a new CDI unit and I now have spark on all 6 cylinders when cranking.....sure enough, the engine now fires right up from a cold start within less than 2 seconds.

Now it appears I have a different problem...the engine stumbles, lacks power and seems to miss when I try a hole shot or any throttle setting higher than 1/4 up....I tried adjusting the rich / lean screws but it didn't seem to matter how rich or lean I adjusted the carbs.

I didn't do the link & sync from clams camino because I don't have a timing light. My next step is to get a timing light and make sure the timing is right.

Any other thoughts or suggestions would be appreciated....is it necessary to set the timing when replacing the stator?

 

[MercFan]

Re: Hard Starting 1988 115hp Mercury Inline 6

start with the link and sync.
Without reading all the posts again:
Does pumping the primer bulb make the problem go away?

 

[CharlieB]

Re: Hard Starting 1988 115hp Mercury Inline 6

Retest your spark, I would NOT replace a stator until I've PROVEN it bad with a DVA Meter.

This problem seemed only to happen 'stone cold'

A bad bias circuit in the ignition module that was working can cancel the ignition pulse from the 'non'working' module.

Test by disconnecting the bias wire from BOTH modules and retest spark
If it NOW sparks on all six then replace BOTH modules, the one that seemed to be working OK has the bad bias, the un-discharged Capacitors in the non-working module have weakened it and it will soon fail.

 

[Jimmy70]

Re: Hard Starting 1988 115hp Mercury Inline 6

I kind of had this problem myself but found the some of the plugs were breaking down, once I replaced those then I was off and running good. The plugs looked new and not abused but apparently they were bad.
Jimmy70

 

[mj1968]

Re: Hard Starting 1988 115hp Mercury Inline 6

I need a stator for the same motor, could you tell me the part number to find it?