Timing mercruiser 140 (181) from 1980

[Niels45]

Hello,
I’m Niels, from the Netherlands and new on this forum. Since 10 years i’ve had several different boats, and now i have a Draco 23 sc (1980) with a mercruiser 3.0 140pk.
The problem i have is with my engine. I Timing is set on 8 gr btdc, and the engine runs ok, but stationaire is sometimes when motor is hot, a little flexibel and to low. The egine drops, but i can start it again. When i put it on load, it stops again. (To less rpm).
When i ajust the timing by ear, to more advance, it runs better (more rpm). The cold start is also much better in this setting. It’s probebly about 14 gr. btdc.
Can anyone tell me of this is a common problem for the Old mercruiser, and is this ready so bad for the engine? The engine seems to run fine on this setting...

 

[Alumarine]

Welcome.
Timing for that motor should be 6 degrees BTDC at 650-700 rpm while in gear.
The dwell for the points should be 28-34 degrees.

Are you sure the carburetoris setup ok?
Idle mixture screw should be set at 1-1/4 turns out as a starting point.
Is the choke opening completely?

 

[Niels45]

Timing issue 3.0 mercruiser 1980

Hello, i’m Niels and new on this forum.
my boat has a 3.0 mercruiser, from 1980.
The problem is the Ignition. Stationaire the enging runs much better at 14 btdc, instead of the 8 gr what’s in the manual. Can anyone explane that to me?

 

[achris]

Engines will run 'better' with advanced timing, at low loads. As soon as the load comes on, the spark is too early, and will knock holes in pistons. It's for this reason that you MUST time an engine with a proper timing light. In the bad ol' days, mechanics timed an engine by ear. Do that with a boat engine, you'll be looking for a new engine (and a new mechanic)...

Chris.......

 

[Niels45]

Thanks for your answer. I know that the timing have to be set on 6 degrees, but the question is why the engine runs much nicer with more advance, and is this normal? I can get it on 6 degrees, but have to Screw the idee set Screw more open. That’s what i think is strange.

 

[Alumarine]

Have you ever removed the distributor?
It could be out by a tooth.

 

[Niels45]

That can be it! So it’s not normal that the engine runs better with more advance timing? Isn’t it better to run the engine as smooth as i can by turning the Distributor?
I don’t know if it’s the problem because if it’s one tooth wrong, when you ajust the timing by lamp, and turn the Distributor Housing, shouldend it be correct?

And how can i check of the Distributor is out by a tooth?

 

[Scott Danforth]

the engine will seem to run better at 14 degress.... at no-load or light load however ......when you load it up (such as in a boat when doing a hole shot), you will also burn holes in all 4 pistons.

put the timing at 6-8 degrees after you file the points, gap the points, and adjust dwell.

 

[Niels45]

Today I run the boat with the 8 gr btdc and it runs fine, but after half an hour running, when it goes to idle, it sometimes runs to low and stops. Not all the time...
When I start the engine I need to give lots of gas, then it runs at 850 rpm, sometimes 650, sometimes 1000. When it’s on 650, and I put it in gear, the engine stops. It looks like there’s no much power in the engine.
So the idle in cold or semi hot conditions is ok, but when hot, it’s a little flexible.
There is a little space between rotor and the shaft. Could that be the issue? Or is it a fuel problem. Leak manifold gasket?
When I turn the engine from load to free, the electric switch to kill the ignition works ok, but maybe it’s not working fast enough. Out of the shift cable to outdrive, leaks a little water. Might the cable be rusty and stocks the working of the ignition kill switch?

 

[Niels45]

I hope someone knows what this can be

 

[harringtondav]

As timing is reduced, the idle speed also reduces. Inverse is the same: more timing advance, higher idle.

Sometimes you have to work between timing and the idle screw. Mechanical timing advance is at play. Reduce the timing to your specification, then adjust the idle speed within specified range. Then recheck/readjust the timing until it and idle speed are at spec.

Your distributor rotor should be pointing at the #1 plug terminal when the timing mark is aligned at the correct advance position. Manually rotate the crankshaft until the timing marks align. You will have to remove the spark plugs to do this. Then use a sharpie marker and mark the distributor body directly below the #1 plug wire. Remove the dist. cap and see what you have. If the rotor is not pointing at the mark, follow marc c advice. Hopefully your manual states how to align your distributor. It is not a very difficult job.

 

[Alumarine]

Here's a link to an online manual in case you don't have one.
http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/0

 

[Niels45]

As timing is reduced, the idle speed also reduces. Inverse is the same: more timing advance, higher idle.

Sometimes you have to work between timing and the idle screw. Mechanical timing advance is at play. Reduce the timing to your specification, then adjust the idle speed within specified range. Then recheck/readjust the timing until it and idle speed are at spec.

Your distributor rotor should be pointing at the #1 plug terminal when the timing mark is aligned at the correct advance position. Manually rotate the crankshaft until the timing marks align. You will have to remove the spark plugs to do this. Then use a sharpie marker and mark the distributor body directly below the #1 plug wire. Remove the dist. cap and see what you have. If the rotor is not pointing at the mark, follow marc c advice. Hopefully your manual states how to align your distributor. It is not a very difficult job.

Thanks for your answer. I followed your advice and checked it. Distributor is not placed wrong and timing is at 6 btdc yet. I had to adjust the idle mix screws a little and the idle screw. It runs ok now, but it stil stops after I have been boating for a while. It will turn off because of to loo idle speed. And that’s not all the time. Sometimes it wi not stop and runs fine.
So what that flux idle speed? Is it something with the carburetor, fuel pressure or what else? The fuel I use is new.
Ignition seem not the problem.

 

[Scott Danforth]

if your distributor shaft upper bushing is bad and there is any shaft wobble, your dwell will change, so your timing will change

make sure the distributor is in good shape
make sure you file and gap the points
make sure you check dwell
set timing
adjust idle mixture
adjust idle speed
re-adjust timing
re-adjust idle speed

go boating