Mercruiser stops running

Got up to the boat last weekend for more trouble shooting. I'm starting to think the problem may be a bad resister wire to the coil. From searching I found the wire should have 1.8-2.0 ohms mine was 4.0 ohms.
So after running for one hour at the dock at around 2000rpms I shut the motor down. Would not restart, then I thought I should hurry up and switch the coil out for the one on the port motor. Fired right up, this is what has me thinking the coil is overheating due to bad resister wire.
I'm not sure how much work replacing the resister is. This has me thinking about splicing a new wire on the boat side of the harness and running this to the + side of the coil. And installing a coil with built in resistance.

Al
 
You indicated when it won't start it doesn't even pop.
Note that the purple resister wire feeding the coil+ terminal when the engine is running is bypassed for full voltage to the coil only during cranking by the purple/yellow wire to that same coil + terminal from one of the small primary circuit terminals on the on-starter solenoid.

It might be worthwhile to try disconnecting the purple resistance wire from the coil + temporarily as test to see if the engine will start and run briefly just while the key is still to Start. If that works there may be a problem with that resistor wire circuit grounding out.

You might also very temporarily jump from battery+ to coil+ , with and without the original purple /yellow wire or purple resistance wire attached as test to see if it starts then.

Keep in mind as mentioned above, if you have the original Pertronix conversion module it is too easy to burn out if you leave the engine off, but ign key to On, while you test for energized ignition items(and it's ...possible... that has already happened since it last started.). Pertronix says the much better Ignitor II apparently does not have that vulnerability.

How did you "repair" the frayed wired to the coil+ you mentioned in your 1st post?
Could the conductor strands be compromised by creeping corrosion and providing excess resistance in that circuit causing heat and more resistance,etc until it burns out, or melts insulation to arc to ground?
Was that the purple resistor wire or the purple yellow from the starter solenoid?

http://www.boatfix.com/merc/servmanl/13/13e4r2.pdf
 
The wire we repaired was combined with another wire to a single connector. In the repair we gave the frayed wire its own connector. I may be wrong but, I think my wiring colors are different being such an old boat (1978). When I tested for ohms I disconnected the harness and with my multi meter in #5 on the harness tested each wire on the + side of the coil until I got a reading. This I figured then had to be the resister wire and it showed 4 omhs v 1.8-2.0 from the manual.
The boat is 200 miles away and won't be back until next weekend.
Thanks for all the help, Al
 
I'm a from-back-in-the-day guy. Back then, there were two special wires in addition to the while-cranking 12V supply to the coil.
1. IF the distributor had vacuum advance, the wire from coil negative to points/condenser was a special flexible wire. Very fine strands, so it could bend again and again, thousands of times, as the advance operate. An electronically-timed system doesn't need that.
2. A resistance wire from ignition run to coil positive. That was if the coil was actually say 9-volt and this wire was the one the engine would run on once the user released the starter. Your system may or may not have that. It may have a coil "with internal resistor" as Charlie mentioned, or a ceramic resistor instead of wire, as Charlie also mentioned. GM seemed to use mostly resistance wire. Chrysler used a ceramic resistor. Ford SEEMS to have used wire...
See what your ignition calls for, which coils you have, and which kind of wire is feeding the system in run mode.
 
Thanks for the input, there is no vacuum advance. Also there is no ceramic resistor but a resistor wire per the manual. This wire is #5 on the harness connector. From this pin I used my multi meter to check the ohms manual says 1.8-2.0 ohms mine was 4.0 ohms
After running for a hour last weekend at the dock I shut the motor down then tried to restart. Would not start, this is when I switch coil from port motor and it fire right up. I my be barking up the wrong tree, but this has me thinking the resistor wire is bad causing the coil to over heat and not working properly.
So what I've been thinking about is at the harness (boat side) cut the wire to pin #5 and splice in a new wire that would run to the + side of the coil. I would also install a coil with built in resistance. The coil on the boat now says "use with external resistor"

Al
 
A handful of ohms, vs hundreds, taxes a meter's accuracy, down around Zero. Short the leads together and it often won't read 0.000. I hope you're getting an accurate reading, but if 4.0 is right, that's twice the resistance called for and your coil gets less voltage than designed for. In some applications, the device wants basically Watts, Volts X Amps. So if it's not getting its Volts, it might draw more Amps, and get hot, while still not producing its designed output (spark) voltage since its input voltage was low...
 
My boat is '78 with 350. It had internal resistor in coil. No external ballast resistor or resistor wire. You can loosen the coil bracket and raise the coil to see if it says internal resistor on the can.
 
The mercruiser manual shows a resistor wire. Its pin number 5 in the harness. I used a multi meter from this pin 5 to the wire at the coil to messure.
The same manual says it should have 1.8-2.0 ohms mine was 4.0 ohms

Al

quote:
Originally posted by jtybt15

My boat is '78 with 350. It had internal resistor in coil. No external ballast resistor or resistor wire. You can loosen the coil bracket and raise the coil to see if it says internal resistor on the can.

Click to expand...
 
wiggle the wire while measuring and see if it changes.
 
Judging from the measurement of the resistance wire, it should be replaced. It can be just a couple inches long or a foot long. You should be able to identify it just by sight.
 
Is there an ignition module inside the distributor, under the cap under the weights, mounted to the base
 
There are no weights/advance. Both motors have electronic ignition conversions installed. I switched these between motors to see if the conversion might be bad. No joy :-(

quote:
Originally posted by Steve the plumber

Is there an ignition module inside the distributor, under the cap under the weights, mounted to the base

Click to expand...
 
Unless the whole distributor was swapped out for a fully electronic one, if the dist originally had centrifugal/mechanical advance I'm not positive but I believe it probably still does with a conversion module. Under the former points plate. I don't believe any of the instructions mention removing that mechanical advance and I imagine it would still effect timing by slightly changing the relative position of the module trigger & sensors. Just no points , condenser or resistance wire/ballast resistor.

If.... the conversion module is a Pertronix marine Ignitor II, any resistor wire must be bypassed to provide minimum 12+VDC to the module when running according to Pertronix. . They sell a 30amp bypass relay(Ignition Power Relay #2001) for that purpose though it can be done without the relay by digging into the harness for the wire. Cat. p. 18 http://www.pertronix.com/catalogs/pdf/ptx/2015/ptx2015_ignition_conv.pdf
 
What's so frustrating is every part (coil, electronic module, cap and rotor) have been switched from the port motor to the starboard. Port runs fine with the parts off the starboard, but the starboard still does not want to restart after running anywhere from 30-60 min.
I was hopeful that the problem was the resistor wire to the + side of the coil. As a work around I installed a coil with internal resistor and ran a hot wire from the + side of the battery to the + of the coil. Ran again for maybe 45 min or so and just like before, would not restart. After sitting for around 10 min or so did restart.
I did have the carb rebuilt last year and now are wondering if that could have something to do with it.
Going up to the boat tomorrow to change oil in preparation for haulout. Sure wish I could of figured this out before, but just not meant to be.

Al
 
When it cuts out or doesn't restart have you actually confirmed there is fuel in the carb ? > With flame arrestor off can you see a good jet of fuel from the accelerator pump? And does it smell nice strong gassy? Does it smell gassy before you advance the throttle for the squirt of fuel?
Have you used the timing light again to confirm whether it strobes while cranking?
Did you try a vac gauge test when it's running?
Fuel pressure test?
Voltage at the coil before and while cranking?
Any abnormal indications on the spark plugs? (White very lean? Or black wet?)
I don't recall you ever mentioned which conversion module you have in there. It makes a difference as to whether there should be any add'l resistance device (including resistor coil) in the circuit after the conversion.
Have the fuel hoses been updated to alcohol-resistant type to prevent, cracks, porosity or delamination? Or are they still 1978? If updated, the date and spec would be shown on the hose stripe.
Was the mechanical fuel pump every replaced with an electric pump?
When it stalls, is it like a switch turning the engine off or somewhat slower loss of power then sputtering off?

My apologies for any /all questions previously asked and answered. Hate to hear you start to winterize without getting this issue squared away for the spring commissioning.

If you confirm proper ignition and timing and still suspect the rebuilt carb , swap them out.
 
There was a complicated case some years back. Geo (GVP) picked it out as the alt. Not that this the same but I'm not an electrical engineer like Geo. Just a thought since the alt is easy to remove and test.
 
Again probably asked and answered, but Key Switch, Kill Switch, Connectors, anything getting primary voltage from Battery/Battery Switch through Ignition Switch, Wiring, etc. to the Primary of the Coil.
 
When the motor would not restart after stopping we did pull the flame arrestor and confirmed it was getting fuel. Went as far as replacing all filter.
When trying to restart we did have the timing light on the coil wire. Would get a couple of flashes then nothing, followed again by a couple of flashes.
Never tried using a vacuum gauge.
Voltage on the coil + side while running is 10V
The conversions have been in the boat for many years and so don't remember the make. But have work without issue until this problem came up. Also switched the conversions between motors and the problem still is there on the starboard motor. Port running fine with the same make of conversion.
I also installed a coil with internal resistor. Ran a jumper from + bat to + coil and ran thinking the resistor on the motor was bad. The problem remain so I put the original parts back.
Change the fuel lines years back and both motors use the same lines except for the last couple of feet where they split.
I'm now starting to think there maybe a ground issue. I did clean the cables at the battery. But with the problem motor (starboard) running and I try starting the port it drags the rpms on the starboard down to the point it could stop running. I have to give the starboard more rpms then the port will start and run fine.
Thanks for trying to help, much appreciated.
Al

quote:
Originally posted by Sandy

When it cuts out or doesn't restart have you actually confirmed there is fuel in the carb ? > With flame arrestor off can you see a good jet of fuel from the accelerator pump? And does it smell nice strong gassy? Does it smell gassy before you advance the throttle for the squirt of fuel?
Have you used the timing light again to confirm whether it strobes while cranking?
Did you try a vac gauge test when it's running?
Fuel pressure test?
Voltage at the coil before and while cranking?
Any abnormal indications on the spark plugs? (White very lean? Or black wet?)
I don't recall you ever mentioned which conversion module you have in there. It makes a difference as to whether there should be any add'l resistance device (including resistor coil) in the circuit after the conversion.
Have the fuel hoses been updated to alcohol-resistant type to prevent, cracks, porosity or delamination? Or are they still 1978? If updated, the date and spec would be shown on the hose stripe.
Was the mechanical fuel pump every replaced with an electric pump?
When it stalls, is it like a switch turning the engine off or somewhat slower loss of power then sputtering off?

My apologies for any /all questions previously asked and answered. Hate to hear you start to winterize without getting this issue squared away for the spring commissioning.

If you confirm proper ignition and timing and still suspect the rebuilt carb , swap them out.

Click to expand...
 
quote:
But with the problem motor (starboard) running and I try starting the port it drags the rpms on the starboard down to the point it could stop running. I have to give the starboard more rpms then the port will start and run fine.
Click to expand...


that sounds like extra load on the stbd alternator. Do they share batteries? Is it possible that the port battery is failing?
If you have any multipin connectors clean them.
 
So you don't have the engines starting and running connected to separate P & S batteries?

Are all the battery negative terminals properly connected together and then the daisy chain connected to clean and tight engine grounds on both engines? There can be a several important engine grounds on each engine.

Some alternators will not start charging until a critical engine RPM is exceeded.

The fact you don't get steady flashes from the timing strobe is certainly not good if the strobe had very good connections.
 
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