Mercruiser stops running

S

ScubaAl

Member
Joined
Jul 31, 2001
RO Number
5559
Messages
48
Well I'm sure this is along shot but I have nothing to loose.
1978 Cruisers Villa Vee with twin mercruiser 228's and BW velvet drives.
The last 2 times I've taken the boat out the starboard motor has quit. This is after running at around 2000rpm's for just over 1/2 hour. Will not restart.
First time back at the dock we do trouble shooting. Using a timing light looks like no spark. Switch coil, replace rotor and cap. Still nothing, then notice a wire on the + side of the coil is frayed. Repair this and the boat started right up. Problem solve, or was it?
Yesterday at about the exact same time frame the starboard motor once again stops running. Again back to the dock. Pull the fuel water separator and a little water but not much (both motors run off the same tank) we replace F/W filter, carb filter and inline filter.
Motor starts up and we let it run. After 35min or so quits again, is something getting hot?
I converted both motors to electronic ignition years back. So switch the electronic pickup from one motor to the other.
Start both motors and run at 2000rpms for 60min no problem. Shut down and decide to take the boat out to be sure. Run the boat up on plane for around 20min or so (3300rpms) and back to the dock, not problems.
Today figure I'll run it again to see what might happen, runs fine for another 60min and I shut the motors down. Decide to restart just to be sure. Starboard would not fire, turned over but no fire. Wait about 10min and now it fires up and runs.
Temp gauges on both motors shows around 140 but could something else be getting hot and causing the problem, electrical or fuel?
Sorry this is so long

Thanks, Al
 
Obviously something is cooling down during your troubleshooting time period. I would think coil, ignition pickup. What about vapor lock for the carb?
 
Do yourself a favor. Carry a spray can of "starting fluid". When your engine does not fire, try some starting fluid...if it fires, you know the issue is most likely fuel. If not, it is most likely ignition.

The third ingredient (fuel, spark, compression) can be verified with a compression test.

It sounds like you're doing all the right things especially using timing light to check for spark. From there, you swapped cap, rotor, coil, checked coil connections. One other suggestion - Also check the ground connection to the engine and battery. Make sure it isn't loose or dirty.
 
Thanks for the replies. Carrying the starter fluid is a good idea. Would go along way to isolate the problem. Coil,cap,rotor along with electronic ignition conversion have all been swapped out and if fact put on the port motor and ran fine.
Saturday after running at the dock for an hour at 2000prms and then going our for a short test cruise I thought things might be fine. Of course not knowing what the problem was is a concern.
But then Sunday I had other plans, but figured I better test out the motors again. So ran both again for an hour before shutting down. Thinking the gremlins had left I was looking up. But before heading for home thought I'd fire up the starboard again just to be sure. Cranked and cranked and would not fire not a pop. Pulled the flame arrestor and moving linkage was getting fuel. Back down in the dumps, after 10 min or so tried again a sure enough it fired up. This carburetor was rebuilt last summer.

Al
 
It definitely sounds like a spark issue, especially if you saw fuel going into the cylinders.
I like the idea of using timing light to verify there is a spark when it won't fire.

Have you changed the plugs and wires? Or at a minimum make sure the wires are clean and seated solid (especially the primary wire from coil to cap)?
 
Plugs are new, installed last fall before haulout also had the carb rebuilt last summer.
Asked the marine to look into it. But no hopeful. Haven't had that good of luck with them. But hoping with all theirs of experience maybe they have come across something like this in the past.
Thanks for the reply, Al

quote:
Originally posted by WALSHIE

It definitely sounds like a spark issue, especially if you saw fuel going into the cylinders.
I like the idea of using timing light to verify there is a spark when it won't fire.

Have you changed the plugs and wires? Or at a minimum make sure the wires are clean and seated solid (especially the primary wire from coil to cap)?

Click to expand...
 
next time it stops check for voltage at the battery side of the coil.

Electronic ign?
 
I installed electronic conversions in both dist. several years back. Have never missed a beat. Also switch the conversions between dist. to eliminate that as the problem.

Al

quote:
Originally posted by pdecat

next time it stops check for voltage at the battery side of the coil.

Electronic ign?

Click to expand...
 
Might as well rule out flooding-condition by trying to start with no pumping and WOT throttle position to get enough air in to reach a combustible ratio. Just be ready to reduce to idle immediately if it fires.

You mentioned you "repaired" the coil supply wire. Was that just taped or exposed section cut out or the wire replaced? As already suggested you should check voltage to the coil+.

Have you used the inductive timing light on the plug leads again when it will not start to check for spark pulse?

If you do use starting fluid (or WD-40), I suggest you try not do that more than once as a quick test to see if you can attain combustion. They remove or thin oil from the rings and cyl walls, especially the ether.
 
If you don't find any other obvious cause, it can't hurt to have someone crank for no more than 10 seconds without a good starter cooldown rest, while you do the sometimes extremely helpful Wiggle Test of all ignition and harness wires to see if it completes a circuit or removes a short & fires up.
 
What ign conversion did you use?

Sounds like coil getting too hot. May be a bad contact that increases resistance that creates more heat.

Does the coil have internal resistor or external resistor? TB ignition doesn't have any resistor and uses specific coil.
 
After the starboard motor quit the first time we changed out the cap and rotor. Also switch the coil from port to starboard. The coil has worked fine on the port motor.
The conversion was Pertronix if I recall, been many years.
This does not have Thunderbolt.
Switched the conversions between motors the one from the starboard side is working fine on the port motor.

Thanks, Al

quote:
Originally posted by jtybt15

What ign conversion did you use?

Sounds like coil getting too hot. May be a bad contact that increases resistance that creates more heat.

Does the coil have internal resistor or external resistor? TB ignition doesn't have any resistor and uses specific coil.

Click to expand...
 
Run the boat again to see if you get a shut down and what motor.Some electrical components are susceptible to heat related failures. The coil is one of them. Often it takes a while for the coil to heat up before it shuts down. Run it til it fails and see how hot the coils get.
 
quote:
Originally posted by jtybt15

What ign conversion did you use?

Sounds like coil getting too hot. May be a bad contact that increases resistance that creates more heat.

Does the coil have internal resistor or external resistor? TB ignition doesn't have any resistor and uses specific coil.

Click to expand...


Maybe the ballast resistor is it. Both sides need it and only one side has it. No matter which coil you swap in there (side with no ballast resistor) it will get too hot and quit.
 
After the first time the engine quit and I was switching out parts the coil was hot to the touch. While switch it out I had to us a rag. Didn't check the second time.
So where is the ballast resistor located?

Thanks, Al

quote:
Originally posted by ddurand

quote:
Originally posted by jtybt15

What ign conversion did you use?

Sounds like coil getting too hot. May be a bad contact that increases resistance that creates more heat.

Does the coil have internal resistor or external resistor? TB ignition doesn't have any resistor and uses specific coil.

Click to expand...


Maybe the ballast resistor is it. Both sides need it and only one side has it. No matter which coil you swap in there (side with no ballast resistor) it will get too hot and quit.

Click to expand...
 
If you have a ballast resistor it would be connected to the coil + in the On/Run circuit and bypassed in the Start circuit to re-gain the full 12+VDC.

If you have the original Pertronix Ignitor ("I") and had a ballast resistor with an original points and condenser system you must retain the ballast resister in the system.

If , on the other hand you have installed the Ignitor II, which is much more robust( doesn't burn out if you leave the engine Off/ignition On to work on the circuits like the Ignitor I), then any original ballast resistor should be removed.

Testing ign. coils:

http://www.boatered.com/forum/topic.asp?TOPIC_ID=51465
 
On points type ign system, the ballast resistor reduced the juice going to the points so they wouldn't melt, literally. Don't know the petronix system so can't comment.

One thing you have to check, is there an external ballast resistor, which is 3" long ceramic block (or resistance wire)with a groove and a coil of resistance wire in the groove. Does the coil also have an internal resistor. It'll say on the can. You don't want BOTH external and internal resistors.
 
if the coil on the failing side was much hotter than the other that is suspicious
 
It was hot, but I did switch the coils between motors. The starboard failed again with the coil from the port motor.
There is no ceramic ballast, but from my research seems it has a resistor wire.
Al

quote:
Originally posted by pdecat

if the coil on the failing side was much hotter than the other that is suspicious

Click to expand...
 
As previously suggested; check the plus side of the coil to ground when in the failing state, with the ignition in the run position. Should be about 9 volts with a resistance ignition. If nothing is there, back up to the ignition switch. Could be a bad connector pin. Any crimp connectors look for black corrosion where the wire joins the crimp.

Ken
 
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