Mercruiser 3.0L EST ignition, won't exit base timing mode.

[havoc_squad]

I have a 1993 Mercruiser 3.0L with EST ignition and I either cannot seem to get it to enter base time mode, or I can't get it out of base time mode.

I did an initial lake test run yesterday and noticed after it warmed up, it was acting rough at idle.

I ruled out fuel initially since it was stabilized fully on winterization and no issues in performance other than idle. Carb is 2 years or less old.

To add to my suspicions that it was timing, I had my distributor jump time on my last year and a reputable mercruiser service center spotted the issue and fixed it.

To confirm this, I did a slight lean adjustment on the carb (1/4 turn) to smooth up the idle, and when under load I turned my drive hard which the power steering puts a load on the engine, I started hearing knocking sounds while the pump was working hard. When I did this in neutral, the no engine knocking occur. Also, the leaner you go, the louder the knocking gets.

So, I went home and researched the service manual, bought a timing gun with RPM gauge on it, and made me a base time mode jumper.

So I get the boat warmed up at home on the muffs, disconnect the shift interrupt jumper wire, then apply the base time mode jumpers to the ports for the distributor.

The current timing shown was I believe -20's BTDC while the jumpers were on. I adjusted it to -1 to -2 ish BTDC, then locked down the distributor, verified that it held, then pulled the base time jumpers out of the ports and re-connected the shift interrupt wire.

The problem is the boat engine's ignition is still stuck at -1 to -2 ish BTDC after setting base time which is causing the engine to run rough at idle, and does not revert to the Mercruiser service manual specified -12 (+/-2 degrees) BTDC at idle.

Is there any way to troubleshoot whether the distributor is going into base time mode and when it exits? If not, is there any way to test components to see if the EST module is defective?

 

[Bt Doctur]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

"To add to my suspicions that it was timing, I had my distributor jump time on my last year and a reputable mercruiser service center spotted the issue and fixed it.

To confirm this, I did a slight lean adjustment on the carb (1/4 turn) to smooth up the idle, and when under load I turned my drive hard which the power steering puts a load on the engine, I started hearing knocking sounds while the pump was working hard. When I did this in neutral, the no engine knocking occur. Also, the leaner you go, the louder the knocking gets.This is news to me ,can you explain it better "

This is news to me. can you explain this type of test?
Timing is done with the motor running , jumper placed at dist, shift interrupt wires joined together, then check /adjust timing.

 

[havoc_squad]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

"To add to my suspicions that it was timing, I had my distributor jump time on my last year and a reputable mercruiser service center spotted the issue and fixed it.

To confirm this, I did a slight lean adjustment on the carb (1/4 turn) to smooth up the idle, and when under load I turned my drive hard which the power steering puts a load on the engine, I started hearing knocking sounds while the pump was working hard. When I did this in neutral, the no engine knocking occur. Also, the leaner you go, the louder the knocking gets.This is news to me ,can you explain it better "

This is news to me. can you explain this type of test?
Timing is done with the motor running , jumper placed at dist, shift interrupt wires joined together, then check /adjust timing.

So, what does the interruptor switch wire get connected to when trying to put it in base time mode? Just to explictly ask so there is no assumptions made.

When I re-looked at the service manual, it seemed very vague on "both wires together".

When I get a chance today, I'll re-look at the interruptor switch wiring.

 

[Bt Doctur]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

manual has you removing the harness wires from the switch and connecting then together

 

[Bt Doctur]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

 

[havoc_squad]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

Understood, disconnect both wiring ends of interrupter switch and join them together along with the other instructions to put ignition in base time mode.

So, before I put the ignition in base time mode in idle, do I need to change the timing while it is not in base time mode during warm idle to -12 to -14 degrees BTDC to correct my screw-up with the interrupter switch, or back to the original screwed up timing of -20 ish degrees BTDC?

Basically, I'm trying to undo the timing adjustment I did while not recognizing that the ignition was not in base time mode. Please let me know what is the safest procedure to correct this incidental timing adjustment.

 

[havoc_squad]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

This is news to me. can you explain this type of test?

I remember seeing a forum topic in a ignition timing thread from Bondo I believe that mentioned that detonation (pinging/knocking) is usually a result of either lean condition or timing.

By leaning out the idle air mixture 1/4 a turn and running at load in the water at idle while turning the boat hard would put the max load on the engine. This is when the knocking occurred, then I turned it back 1/4 turn richer to the original position when the boat had originally ran perfect at idle in load.

That let me know that I was getting enough fuel/air mixture at the original setting, as no knocking occurred with the same test. The problem was something else than idle fuel/air delivery causing it to run rough in load at idle.

Last year the same issue occurred, only a lot worse the previous year. Last year the boat's idle would eventually cause the engine to slowly choke and die in idle due to messed up timing.

 

[havoc_squad]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

So I reset the timing mistake back to about 14 to 16 BTDC, probably about 4 to 8 degrees better than the original timing spot (20 or more degrees BTDC) that I found it.

Then I fixed the missing step and the ignition fully went into base time mode, and I was at either 2 or 1 degree BTDC. It's hard to tell with a huge chunk mark for the crank pulley timing mark.

Pulled out of base time mode, and the timing reverted back to normal, same as before (roughly 14 to 16 BTDC). Runs a ton better than beforehand.

Do I need to try and see if I can get the base timing mark closer to 1 BTDC to get to 12 to 14 BTDC when it is out of base time mode? Or is this margin of error sufficient for "Good enough"?

 

[havoc_squad]

Re: Mercruiser 3.0L EST ignition, won't exit base timing mode.

After thinking it over, I messed with adjusting the timing again in base timing mode and was able to get it really close to 1 BTDC.

Now the timing in idle in normal mode is 13 BTDC to 14 BTDC, well within specs.

Grabbed it and shoved it in the lake, slight carb adjustment to add a very very small more richer mix.

Now it idles excellent and super smooth (for a 3.0L) after a high speed lake run, as most idle issues show up after a speed run and reduce down to min idle in load.

Now I just gotta deal with (remove & replace) a most likely crappy power steering pump making noise.