Mercruiser 3.7 points continue to fail

[br223899]

Hey guys. These forums have help me multiple times, however this is my first post. I have a 1988 Mercruiser 3.7 with an issue with the points. I've had terrible luck with these. One day I decided to change the points / condenser / cap / rotor for preventative maintenance using a kit from west marine. A set of automotive points, etc were previously installed from the original owner. I couldn't get the engine to run afterwards, so I reinstalled all the old points, etc, again. Everything ran fine afterwards.

I figured I got a bad set or something, so I bought another set from another marine store. This time the engine ran fine. However, after a few operating hours, the engine quit on the lake. I finally determine there wasn't any spark, and traced it to the points. I tested by rotating the engine to open the points. Then I used a screw driver to short the contacts on the points to simulate the points opening and closing. The coil had great spark. Then I rotated the engine to close the contacts, and used a set of pliers to physically open and close the points. This time, there was a very poor spark.

Off to West Marine to buy another set of points. No cap / rotor etc this time, but I bought a new coil. Afterwards, I had great spark shorting the points with the screw driver, and physically opening with a pair of pliers. It ran fine again. However, after a few hours, guess what. I was left on the lake again. Same issue after I tested everything.

This time I decided to buy a set of automotive points / cap / rotor / condenser, etc just like the original owner had. Same part numbers and everything from Autozone. It started and ran great for the remaining of the season last year. Today I tried to start it after being in storage. It ran fine for about 5 min, then stopped. Same issue. Tested the points, and they're junk again.

Everytime I change these, the dwell and ignition timing is set perfectly. I never leave the ignition key on while the engine is not running. Something seems to continually ruin the contacts on these points. I pay fairly close attention to the voltmeter on the instrument cluster, because I know of the voltage regulator issue on this motor. I've never seen it above 14 volts. I also thought about the purple resistance wire having something to do with it, but looks alright visually. I've thought about, and am very willing to install a pertronix electronic ignition conversion kit. However, I don't understand the root cause of the issue, and I'm afraid I'll burn up the pertronix unit. Any ideas?

 

[Bt Doctur]

Re: Mercruiser 3.7 points continue to fail

sounds like a bad condenser and you don't mention changing it. Also check the voltage at the + side of the coil with the engine running

 

[thumpar]

Re: Mercruiser 3.7 points continue to fail

What is the voltage at the coil? It should be 7-9 volts. If it wasn't running through a resistor wire or resistor it could cause the problem.

 

[stonyloam]

Re: Mercruiser 3.7 points continue to fail

Your points probably glazed over during the winter, ( happened to me) a new set of points should do it. If the points look burned then the condenser could be the problem. You could pick up a points file and freshen up the points surface (sandpaper can leave grit on the points and cause problems). I switched to a Petronix Ignitor II, 91146A and Flamethhrower II, 45011 (oil) 45111 (epoxy). Just replace the purple resistance wire with a stranded 12ga stranded copper wire spliced to the purple wire going to the choke. Good luck.

 

[br223899]

Re: Mercruiser 3.7 points continue to fail

Thanks guys. I'll check the voltage after work today.

The condenser has been changed several times. Every time I bought a kit, I've changed it.

Concerning the Petronix Ignitor II unit, you mentioned 2 part numbers for the coil, one being oil filled, the other epoxy. Is one better or worse for a boat application? I remember reading the difference between the two, however I can't remember.

I understand bypassing the purple resistance wire for the Petronix unit. However, it looks like another wire is connected to the + side of the coil, which goes to the starter. I'm not sure what it's for, but it essentially gets power from the same purple resistor wire, and should be 7-9 volts. Should I leave this connected to the purple wire (so the starter sees 7-9 volts in this particular area), then run a separate wire for the coil (so it sees full 12 volts)? Or should I just install the new purple bypass wire, and allow a full 12 volts to both the coil, and the other wire going to the starter? Does it even matter?

 

[gm280]

Re: Mercruiser 3.7 points continue to fail

Thanks guys. I'll check the voltage after work today.

The condenser has been changed several times. Every time I bought a kit, I've changed it.

Concerning the Petronix Ignitor II unit, you mentioned 2 part numbers for the coil, one being oil filled, the other epoxy. Is one better or worse for a boat application? I remember reading the difference between the two, however I can't remember.

I understand bypassing the purple resistance wire for the Petronix unit. However, it looks like another wire is connected to the + side of the coil, which goes to the starter. I'm not sure what it's for, but it essentially gets power from the same purple resistor wire, and should be 7-9 volts. Should I leave this connected to the purple wire (so the starter sees 7-9 volts in this particular area), then run a separate wire for the coil (so it sees full 12 volts)? Or should I just install the new purple bypass wire, and allow a full 12 volts to both the coil, and the other wire going to the starter? Does it even matter?

I read the comments thus far and wonder what is wrong with the points every time you check them? Are they burnt, closed, bent, or what? Reason I ask is it sounds like you don't have an oiling pad to lube the cam and keep from wearing the point's rubbing block down causing the engine to stop. Are the bad points rubbing block worn? Maybe you need to either apply a very small amount of some grease on the cam lube... Take some pictures and post them so we can see what you can see...

 

[stonyloam]

Re: Mercruiser 3.7 points continue to fail

Concerning the Petronix Ignitor II unit, you mentioned 2 part numbers for the coil, one being oil filled, the other epoxy. Is one better or worse for a boat application? I remember reading the difference between the two, however I can't remember.

I understand bypassing the purple resistance wire for the Petronix unit. However, it looks like another wire is connected to the + side of the coil, which goes to the starter. I'm not sure what it's for, but it essentially gets power from the same purple resistor wire, and should be 7-9 volts. Should I leave this connected to the purple wire (so the starter sees 7-9 volts in this particular area), then run a separate wire for the coil (so it sees full 12 volts)? Or should I just install the new purple bypass wire, and allow a full 12 volts to both the coil, and the other wire going to the starter? Does it even matter?

The epoxy coil is supposed to be more rugged, but I don't think it makes much difference. That other wire should come from the slave solenoid and bypasses the resistance wire during starting which provides battery voltage directly to the coil. It must be connected. Just remove the purple resistance wire, and run the new wire to the coil. Everything else stays the same.

 

[JerryIrons]

Re: Mercruiser 3.7 points continue to fail

Any ideas?

If you are going to stay with points and a condenser, try using the mercury brand and see what happens. What are your values for dwell anyway that you are using?

I need to replace my voltage regulator, it runs on the high voltage side, but if I run some accessories, that keeps the voltage down lower. The point I am making is that even with a wacky voltage regulator, I don't have point trouble like you are having.

Clean off some grounds and contacts. New spark plug wires? Only other thing to try is a different coil, but that's just something to try as a guess.

Post some pics, we like pictures here!

 

[MikDee]

Re: Mercruiser 3.7 points continue to fail

Thanks guys. I'll check the voltage after work today.

The condenser has been changed several times. Every time I bought a kit, I've changed it.

Concerning the Petronix Ignitor II unit, you mentioned 2 part numbers for the coil, one being oil filled, the other epoxy. Is one better or worse for a boat application? I remember reading the difference between the two, however I can't remember.

I understand bypassing the purple resistance wire for the Petronix unit. However, it looks like another wire is connected to the + side of the coil, which goes to the starter. I'm not sure what it's for, but it essentially gets power from the same purple resistor wire, and should be 7-9 volts. Should I leave this connected to the purple wire (so the starter sees 7-9 volts in this particular area), then run a separate wire for the coil (so it sees full 12 volts)? Or should I just install the new purple bypass wire, and allow a full 12 volts to both the coil, and the other wire going to the starter? Does it even matter?

Wait! The Other wire on the coil + side is the 12V. Start/Crank wire from the key switch, to help when starting. It is not powered (dead) on Run. That's when your Resistor wire takes over. You must run a separate 12V. Ignition powered wire for the Pertronics, usually from the electric choke.

 

[br223899]

Re: Mercruiser 3.7 points continue to fail

Well, I tried to get a voltage reading on + side of the coil today; however, the engine wouldn't start. I bought another set of points, installed, and the engine started right up. For reference, the dwell reading on the old points was slightly over 30 deg. So, they were adjusted correctly.

With the new points, it was running a little rough. However, I was running out of daylight and just wanted to get a voltage reading. The dwell was high, 36 deg, and who knows where the timing is. I'll dial it in tomorrow. But, my voltage reading from the + side of the coil to a ground was 12.8 volts. Not 7-9 volts. Seems high. It was not running very long, but the temperature gage started to raise a little.

You guys said the purple/yellow wire off the starter slave solenoid supplies 12 volts to the coil only while the key is in the "crank" position. When the key is in the "on" position, this wire isn't supposed to supply any voltage. Correct? I guess my next step is to remove the purple/yellow wire from the slave solenoid, and check to see if any voltage is coming from that particular post when the key is "on." If I have voltage, that's bad because it's always sending full 12 volts to the coil.

I also have some pictures of the points I just removed. They are virtually brand new, and look it too I installed these last Sept, and have a few hours on them. The part that rides on the cam is fine. The contacts do have a mark on them. I tried to get a picture. I'll post the pictures once I figure out how to do it. There was also a question about the condenser. I've replaced the condenser several times too with no luck.

Even though the engine started on the new points, I don't expect it to last. I've been fooled too many times.

 

[br223899]

Re: Mercruiser 3.7 points continue to fail

Try this.

Boat Points Slideshow by br223899 | Photobucket

 

[Bt Doctur]

Re: Mercruiser 3.7 points continue to fail

considering the higher voltage at the points could the PO have installed regular wire to the coil and not resistor wire?
You could install a Chrysler ballast resistor in series with the coil + side to lower the voltage.

 

[MikDee]

Re: Mercruiser 3.7 points continue to fail

Yes, take the yellow/purple wire off, then put the Red probe on the wire, & the Black to ground, check with ignition key in Start/Crank mode for 12volts.

Then next, keep it all hooked up, & check for Voltage with ignition key on RUN.

Let us know what you find?

Then take off the other wire to the coil, & test it the same way.

See what that reads?

 

[br223899]

Re: Mercruiser 3.7 points continue to fail

I checked voltage at the starter solenoid.

Key on - Purple/yellow post (wire not attached) 0 volts.
Crank - Purple/yellow post (wire not attached) 12.8 volts. Appears to be working correctly.

Key on - Purple/yellow wire (not attached to solenoid) 11.8 volts. Engine not running.
Crank - Purple/yellow wire (not attached to solenoid) 11.8 volts. Engine not running. Appears to be working correctly.

 

[br223899]

Re: Mercruiser 3.7 points continue to fail

However, there is something else I discovered. Check out this video I made. There's a little bit of play on the distributor shaft. What do you think?

http://youtu.be/m5C7n1QX5-0

 

[thumpar]

Re: Mercruiser 3.7 points continue to fail

You need to measure voltage at the coil. It should be 7-9 volts on the run position.

 

[Fishermark]

Re: Mercruiser 3.7 points continue to fail

I watched your video - your bushings are shot in the distributor. Time for a new one.

 

[stonyloam]

Re: Mercruiser 3.7 points continue to fail

+1, I found a shop to rebuild mine. New bushings and checked the advance curve.

 

[MikDee]

Re: Mercruiser 3.7 points continue to fail

You need a new Distributor. I had that happen to me many years ago, I replaced it. Now, I check every vehicle I get for that issue.

 

[br223899]

Re: Mercruiser 3.7 points continue to fail

Yeah, I thought the lateral movement in the distributor shaft was a little excessive. I see where it could effect the timing. It barely starts right now. Once I get this fixed, I'll revisit the voltage issue.

I've seen in the past, especially with carburetors, rebuild companies mail you a rebuilt carburetor, and your original is mailed back in. I tried searching for something like this for distributors, but haven't found anything yet. Do you guys happen to know of any place like this? I buy a new rebuilt distributor, and I in turn mail my original to be rebuilt for the next guy.

I'm just looking for options. I plan to visit a few local places tomorrow to see if they rebuild this in a reasonable amount of time.