Trouble setting correct timing

[aaronw78]

I have a 140 Mercruiser that I've been trying to tune up. So far in the past year I've rebuilt carb, changed spark plugs, fuel filter, lower unit on outdrive and of course oil. It run ok but sometimes it backfires through carb at WOT and top RPMs is only 4000 on glass, a little less on chop. So I suspected the timing might be off, but when I checked it the mark on the balancer was nowhere close to the marks on the timing tab. When I start to turn the distributor to try to match them up the engine starts to idle rough then dies, so then I just adjust back to where it was to begin with. Anybody knows why this is? I am idling the engine as slow as it can (about 600rpms) and clamping light to #1 spark plug. any help would be appreciated. Thanks.

 

[rodbolt]

Re: Trouble setting correct timing

what ign system do you have ?

 

[aaronw78]

Re: Trouble setting correct timing

what ign system do you have ?

As far as I know it's just the standard ign system w/points I haven't opened up the distributer yet to see how it looks inside. BTW I've owned this boat for a little over a year.

 

[Don S]

Re: Trouble setting correct timing

As far as I know it's just the standard ign system w/points I haven't opened up the distributer yet to see how it looks inside.

Until you know for sure, it's impossible to say. Pull the cap and look. There is a lot of difference between timing for a points ignition and an EST, and they are both STANDARD ignition systems on a 140.

 

[aaronw78]

Re: Trouble setting correct timing

Ok, I'll pull off the cap tomorrow and have a look. Thanks for the quick reponses.

 

[calwldlif]

Re: Trouble setting correct timing

Timing will effect idle speed.
If the timing was so far off from
previous owner that carb was adjusted
for that setting, it is entirely possible
that the carb will need readjusting.
this involves air mixture as well as
idle stop.

 

[aaronw78]

Re: Trouble setting correct timing

Popped off the cap today, looks like the ol' points system.

 

[aaronw78]

Re: Trouble setting correct timing

 

[Reel Poor]

Re: Trouble setting correct timing

Before you set the timing, set the point dwell to specs, then set timing.

 

[Alumarine]

Re: Trouble setting correct timing

Is it possible that the distribitor was removed and put back in a tooth off?

 

[freddyray21]

Re: Trouble setting correct timing

a tooth off won't affect it you can move the dist to adjust the timing if it's only that far off. I agree start a base adjust dwell, carb idle then set time. readjust carb if needed to set time. Fred

 

[crazyray]

Re: Trouble setting correct timing

it is possible that balancer has slipped. insure that when timing marks are aligned that motor is actually at tdc. can check thru plug hole with short piece of wire.