1987 Mercruiser No spark after warmup

[Kyle8973]

Hello,

I have a 1987 Wellcraft 190 Classic with a 1987 Mercruiser 165hp MCM sterndrive. I have provided a pic of my serial number below. All summer I have been dealing with the same issue. I have a brand new pertronix ingnition, flamethrower coil with 3ohm resistance, I ran 12volts straight from the choke and cut out the resistance wire.

When the engine is cold it fires right up and runs with no issues for about 20 minutes or so then starts to miss cylinders and finally dies. I then am unable to get consistent spark. I plug a timing light up to the wires to check for spark and when cranking I only get spark ever couple seconds as opposed to a consistant flashing light.

The Pretronix a d flamethrower coil were installed in attmept to remedy this situation but it just continues. I have check ground wires but at this point I am out of ideas.

And assistance, ideas, or thoughts would be greatly appreciated.

Thanks

 

[alldodge]

The Petronix is one of the worst ignition systems out there. I would suggest going with Delco EST

Otherwise, get another Pet pickup and try again

 

[Kyle8973]

Thank you for your response. I went ahead and pulled the electronic ignition and switched it back to brand new points and condenser to see if this would fix my problem. It did not.

I gapped the points at .022 as the motor specs state to use .018 - .025.

I was able to run one again for 20 minutes or so. I then lost power. At 3/4 throttle I was barely at 1500rpm. It would fluctuate like this randomly giving me little boosts in power until it just completely died. It also sounded like I had some backfiring (3 or 4 times) in the carb when it was sputtering out.

Before I took it out this time I started out at the dock and allowed it to idle at about 1500 rpm for 10-15 minutes. It did fine. It wasn't until I was up to 3000-3500 rpm for ba while while driving around that it crapped out on me.

Could It be out of time? Would that cause this type of issue? How do I Set the timing?

I am at a loss.

 

[Scott Danforth]

part of servicing points is filing them, gaping them, verifying the dwell, and setting the timing. as adjusting the gap changes the dwell, and changing the dwell changes the timing.

you use a timing light to set and verify timing

 

[alldodge]

Just dawned on me this is a 3.7, the 165 had me thinking of a in line 6, you did list the SN but I still went right past it

To set timing, connect to cylinder #1 and adjust distributor to 4* BTDC

Think there is a problem with voltage level from the alternator. Jumping from the choke to the coil will not by pass the issue if there is a problem. Put a meter on the coil positive and watch if it starts changing. My guess is the alternator is heating up and causing the issues.

 

[Kyle8973]

I have not had an opportunity to work on my boat yet since it is getting close to Winter, I will most likely be Winterizing the boat soon. However, I have spoken to a couple other mechanics about this issue and was given the following information that I was hoping you all would be able to verify for me.

1. This particular boat motor may not be chain driven but gear driven. Someone I spoke to thought that this particular motor may be gear driven, therefore, the timing would not be set by the turning of the distributor and that the only thing that would really affect the timing is the gap of the points, which I may not have done correctly. Can this be verified using my serial number I previously provided?

2. This motor may have a resistor wire that connects the alternator to the coil. As I previously mentioned, I removed the resistor wire that goes from the choke to the coil, could there be another one somewhere? The person I spoke to said that it went from the Alternator to the coil and it was not the same as the one from the choke. He said that some of these older boats were designed to run on 6 volts as opposed to 12 volts and that resistor wire breaks down over time and stops allowing the proper voltage to the coil when warm. As I mentioned, I already bypassed the resistor wire from the Choke, as the new coil I have has an internal resistance of 3ohms. Can the presence of this additional resistance wire be verified by the serial number? Could this be the issue? How can I test this theory, or the alternator itself without bring it to a Autozone, or similar?

Thanks in advance!

 

[Bt Doctur]

The 470 is chain driven. If you reverted to points/condenser you need a resistor in the circuit.The points and condenser will burn up.
If you have a internally resisted coil you can run a jumper from the + battery to the + coil to see if the motor cuts out. Either the coil is breaking down internally or you have a fuel issue or a bad condenser issue
If you have the alt conversion put a meter on it. If you still have the original stator system put a meter on the battery

 

[nola mike]

I have not had an opportunity to work on my boat yet since it is getting close to Winter, I will most likely be Winterizing the boat soon. However, I have spoken to a couple other mechanics about this issue and was given the following information that I was hoping you all would be able to verify for me.

1. This particular boat motor may not be chain driven but gear driven. Someone I spoke to thought that this particular motor may be gear driven, therefore, the timing would not be set by the turning of the distributor and that the only thing that would really affect the timing is the gap of the points, which I may not have done correctly. Can this be verified using my serial number I previously provided?

Incorrect. Timing is set by the distributor.

2. This motor may have a resistor wire that connects the alternator to the coil. As I previously mentioned, I removed the resistor wire that goes from the choke to the coil, could there be another one somewhere? The person I spoke to said that it went from the Alternator to the coil and it was not the same as the one from the choke. He said that some of these older boats were designed to run on 6 volts as opposed to 12 volts and that resistor wire breaks down over time and stops allowing the proper voltage to the coil when warm. As I mentioned, I already bypassed the resistor wire from the Choke, as the new coil I have has an internal resistance of 3ohms. Can the presence of this additional resistance wire be verified by the serial number? Could this be the issue? How can I test this theory, or the alternator itself without bring it to a Autozone, or similar?

Thanks in advance!

Incorrect again on several counts. Standard 12v system, though they originally were charged via a stator like an outboard rather than an alternator. An alternator conversion is common if the voltage regulator burns out. The only resistor wire is from the choke to the coil. If this is happening with 2 coils, points/electronic, only common cause would be voltage to the coil. Have you checked for 12v at the coil when this is occurring? And actually, that still wouldn't do it if you have the original wiring. The slave solenoid will supply the coil with a full 12v while cranking, so if you're not getting spark both during cranking and running, that doesn't make sense.

To confirm:
1. Problem only occurs when hot
2. Verified that you're losing spark while underway and running, as well as during cranking
3. Same problem occurs when using original coil/resistance wire/points as well as new coil/pertronix?

 

[Kyle8973]

I took a friend of mine with me to winterize the boat this weekend as he is a mechanic and has a good amount of experience with older motors with points/condenser etc.

Nola Mike -
1. Correct, the issue only occurs when hot. I can start the boat on the first turn of the key cold every time.
2. I have verified that I am losing spark when the engine quits by connecting a timing light to the wires when attempting to restart the engine once it dies, and no spark is being sensed by the light.
3. The same issue occurred under the following scenarios in this order this season.

1. Resistor wire in place, OME Points, Condenser, and Coil - However, this was before I replaced the points and condenser, so it may have been due to bad points and condenser. At the beginning of the season, I went straight to the electronic ignition this spring, under the assumption that it would resolve all my issues.

2. Pertronix Electronic Ignition, Bypassed Resistor Wire, Flamethrower Coil with 3ohm built in resistance. (I did run this setup without the bypassed resistor wire first, do you think I burned up the electronic ignition, so that by the time I did finally bypass the resistor wire the electronic ignition was crapping out?)

3.Resistor wire bypassed, OME Points, Condenser and Flamethrower Coil with 3ohms built in resistance. (based on Bt Doctur's comments I probably should not be doing this to prevent burning up the condenser) This is my current setup, with the points and condenser I replaced this year.

With my friend there, he was able to help me with the timing, hopefully, correctly. We set my Light to a 8 degree advance, and ran the engine at idle (~700RPM) then made sure that it lined up with the middle mark on engine. (I am not really sure if this correct or not, but the label on the head said that the timing should be at 8 degrees advance.

Is the engine timing supposed to remain in time as you rev up the motor? Mine seemed to move to the left quite a bit. In fact it did not line up with any of the three marks on the engine.

My friend was able to deduce that I have a misfire and said that it seems to be in cylinder 3, which he was able to determine by watching the light patterns.

He also noticed that when I put the distributor cap on the distributor after replacing the points and condenser that the condenser wire was smashed from being caught under the cap when I put it back on. He also noticed, that inside the cap, there seemed to be some burn marks on the contact points in the cap, and around it a bit.

I am thinking of starting from scratch next season with the following setup.

New tune up kit, Points, Condenser, Rotor, Cap, and Spark Plugs. Then redo the timing and possibly the dwell.

Should I replace the coil with a stock coil, and rewire the resistor wire?
Did I screw up the resistor wire by cutting it out?
Can I buy a new resistor wire somewhere?
How do I tell if my coil is bad? Maybe between me switching everything around with the electronic ignition, and the resistor wire I screwed it up?

Also, will a dwell meter help me? Does anyone have a recommended meter that they have purchased off Amazon that isn't too expensive. They all look like Multimeters to me, but the reviews seem to lean towards them not working well.