Mercruiser 140 Points to Delco EST results in low RPM at WOT

[alldodge]

Its mercruiser service manual number 10. Its not in the stickies , might find it online or on ebay

 

[me78569]

Got ya.

Well I got it all wired up and then the starter started making a terrible noise and the key stopped cranking so I threw in the towel for the day.


Thanks again. I'll report how it runs when I get it back in the water.

 

[j cat]

Got ya.

Well I got it all wired up and then the starter started making a terrible noise and the key stopped cranking so I threw in the towel for the day.


Thanks again. I'll report how it runs when I get it back in the water.

remove the starter .. the motor armature shaft bushing is worn . also inspect the brushes and commutator ..
actuator gear could get binding ..

 

[Eric 3.7LX Alpha 1]

Just a quick little windows trick, if anyone wants to know how to make the ° symbol for timing or temperature, it's holding the ALT button down and press 0176, then release ALT.

 

[Tail_Gunner]

I think I have found your problem. Your engine is specéd for a total advance of 36 degrees, not 23, that is for the later 140s...

You've removed 13 degrees of advance out of the engine, little wonder it's only making 3600rpm.

View attachment 358365

You have match the curve, 12 initial and 24 electronic advance.

Shift Interupt (old style) with new Delco EST Distributor hookup

I originally had a 1985 Mercruiser 140 GM engine, which I replaced with a new GM 3.0 engine (4 cylinder). It came with a new GM Delco Voyager EST Distributor. The instructions I got for hooking up the shift interrupt switch are probably for a newer style system than what I have. I was wanting to...

forums.iboats.com

 

[me78569]

It's been awhile, but I wanted to update this just in case someone else has the same issue. I have base timing set to ~12* and I am now able to rev out to ~4100 rpms which is much better than it was last year. I do have a strange marble like noise at a specific lower rpm that I need to check into tho.

boat runs much better and I no longer have an offidle bog. I will likely try a bit more timing to see if I can gain back some more up top, but I am happy enough to leave it as well.

 

[Scott Danforth]

That marble sound is most likely detonation which is your motor eating itself

 

[me78569]

Yep, it's on the list to dig into. Gonna have to figure out a method to have a broader timing curve.

 

[Scott Danforth]

Yep, it's on the list to dig into. Gonna have to figure out a method to have a broader timing curve.

The 3.0 is limited on how far you can advance the ignition. Exceed the limit and the motor eats itself

 

[me78569]

Total timing that old 140's want is much higher than 3.0's. The book calls for 36* up top vs 24* for a 3.0

The est ignition doesn't have enough advance to get the total timing the engine wants up top.

 

[Scott Danforth]

Timing with est is -1 degree ,( the Dizzy takes it from there). Max timing on an inline motor is about 28 degrees

 

[Tail_Gunner]

The fact it turns up the rpm is good, those marble sounds are bad. Mr. Danforth is correct stop right there.

But I will ask just out of curiosity what size prop is on that boat along with weight and length...prop and boat description.
it is odd advancing timing cuts the bog..running very lean?

 

[achris]

If you try to get the same timing advance into a late model 3 litre as was with the early models, you'll destroy it. You're using extra (ignition) advance to mask a deeper problem, which will not end well.

Chris....

 

[me78569]

My boat has a old 140, I swapped in a electric est ignition. My motor wants the higher timing advance that the points ignition did.

 

[Scott Danforth]

The motor has the same architecture. The same bad head design. The same bad combustion chamber. Your old points dizzy was set to 4 degrees of base timing with a maximum advance of 24 degrees for a total timing of 28.

The est dizzy will adjust up to 28 degrees.

 

[me78569]

The motor has the same architecture. The same bad head design. The same bad combustion chamber. Your old points dizzy was set to 4 degrees of base timing with a maximum advance of 24 degrees for a total timing of 28.

The est dizzy will adjust up to 28 degrees.

From Post #10

Mercruiser 140 Points to Delco EST results in low RPM at WOT

I've been banging my head on the wall trying to figure out how to solve my low RPM at WOT issue that happened after I replaced the points with a Delco Est ignition. I've got a 84 crestliner with a merc 140, serial A330922, the boat got a replacement 140 to replace the blown up older 370 that...

forums.iboats.com

Is the above not correct for my serial number engine?

I am not arguing about the marble sound and it being bad, just trying to sort out conflicting information for what the points system had for total advance on my motor. Tonight I am going to verify base timing then back it down to 6-8* and retry and see if marbles are gone and what rpm it pulls to.

 

[Scott06]

From Post #10

Mercruiser 140 Points to Delco EST results in low RPM at WOT

I've been banging my head on the wall trying to figure out how to solve my low RPM at WOT issue that happened after I replaced the points with a Delco Est ignition. I've got a 84 crestliner with a merc 140, serial A330922, the boat got a replacement 140 to replace the blown up older 370 that...

forums.iboats.com

View attachment 362134


Is the above not correct for my serial number engine?

I am not arguing about the marble sound and it being bad, just trying to sort out conflicting information for what the points system had for total advance on my motor. Tonight I am going to verify base timing then back it down to 6-8* and retry and see if marbles are gone and what rpm it pulls to.

I would check the plugs to see if you are lean as well.

 

[82 baretta]

I'm definitely interested in this as well. I did the same thing and swapped in a delco EST in place of the original distributor. Our motors are the same series, which is the 140. When I set my base timing to 8 degrees BTDC, after taking it out of base timing mode it reads at about 16 degrees BTDC, which seems too advanced to me. It will reach the full 27 degrees by 2.2k rpm, but I still think that the original timing is a bit too much.

There's a bunch of conflicting info on which is the best, set base timing to what's on the valve cover, in our case that's 8 degrees BTDC, or do the 1 degree BTDC, which I don't think we will end up at the correct total advance. I haven't been able to run it under load yet as I have been doing a full resto at the same time

 

[Tail_Gunner]

Finding a baseline for your engine should be quite simple or...can...be would be better said.

Per Mr Danforth posted spec set your static timing to 4 degrees.

Next stop unhook your throttle linkage and adjust your idle down to 650/700 rpm. By now you should be aware of the idle speed screw and the idle metering screws. Generally speaking one starts with the idle mixture screws getting a smooth idle. Next is to turn the idle speed screw to say 700 rpm. Getting your carb to run on the idle circut is just as critical as the timing itself. This is critical the metering screws always determine idle quality and speed. Again trim the metering screws to a smooth idle and lower the rpm with the mechanical idle screw... When a carb is on its idle circut those run the show. If they do not run the show the carb is not on the idle circut, meaning at any time you should be able to screw the metering screws closed the engine dies.

If your carb will not run/using the above you have a fuel metering issue. Just like your distributor, your carb has a curve. The carb must be on it's idle circut to start it's functional curve.

It is entirely possible for the carb to function somewhat off it's idle circut, and the reason for decoupling the carb from the linkage.

linkages off set the carb, once done reattach the linkages. If the rpm varies once done, then you need to adjust your linkages, they are out of adjustment.

If your engine responds well to the above you should be done.

Rochester Quadrajet Idle Mixture Screw 1.265

www.carburetor-parts.com

 

[me78569]

If I set my static timing to 4* my total timing ends up being ~28*, and my max rpms are ~3600-3700 rpm, which makes sense when I look at the spec on timing for a below 0C856558 serial number motor. The boat runs fine just doesn't have any top end.

What I really would like to know is why is there such a big difference in the called for timing on early 140 motors vs late motors? My gut feeling here is the Delco EST just doesn't have the timing advance range needed to have both good timing down low and enough timing for 4000+ rpm for the early model 140 engines.

If that is the case it is fine I just want to know that is what caused my motor to go from 4400 rpm at WOT to 3600 RPM at WOT when the only change was the Delco EST and base timing set at 1*.

I am going to play with it more and see if I can find a happy place without knock and still having some top end.