distributor cap problem

tavacska

Petty Officer 1st Class
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Jan 21, 2017
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244
Finally I get to know it is the problem of distributor cap. It is a 1977 Mercury 1150 L6 with distributor.

For the problem that happened two months ago, I have changed the switch, trigger, coil and the starter. And I also cleaned the carburetor again which I did 4 months ago.
But it still can not be started.

I checked the spark, all of them, it sparks now and then, not consistent at all. Then I connected the high-tension line, which comes out from the coil, directly to the in-line spark tester. It sparks strong and continuously. As a conclusion, the problem comes from distributor cap. And I don't know how to solve it.

1. the spring carbon piece was changed 6 months ago new
2. The trigger was changed, but the rod is the same, and no obvious damages. And the trigger plate was installed exactly as instructed. I bought the CDI-trigger.
3. The distributor cap is never cleaned, do I have to clean the tips inside it?

Any suggestions are appreciated, thanks.
 

tommarvin

Ensign
Joined
Nov 22, 2015
Messages
999
Yes the contacts have to be clean on the distributor,you have changer so may expensive parts already I would get a new cap rotor condenser and everything else I cant think of.
The spark needs to spark consistently, clean the sparkplug electrodes with a tooth brush and cleaner,regap.
There's so many posts about dirty carb problems, that I would remove the carb take it to the bench and take it completely apart, and clean everything,if there's a welch plug remove it, there's small holes in there, get a rebuild kit with new gasket if think you need it.,
 

GA_Boater

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May 24, 2011
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49,038
You don't see a problem?
brush.PNG

The rotor is busted, too.

rotor.PNG
 

tavacska

Petty Officer 1st Class
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Jan 21, 2017
Messages
244
You don't see a problem?


The rotor is busted, too.

I pulled the carbon rod out to show it is intact.

That part of rotor was damaged when I tried to remove it from the trigger. But only that part was damaged long time ago and everything works good after that for a while.

Thanks.
 

tavacska

Petty Officer 1st Class
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Jan 21, 2017
Messages
244
Yes the contacts have to be clean on the distributor,you have changer so may expensive parts already I would get a new cap rotor condenser and everything else I cant think of.
The spark needs to spark consistently, clean the sparkplug electrodes with a tooth brush and cleaner,regap.
There's so many posts about dirty carb problems, that I would remove the carb take it to the bench and take it completely apart, and clean everything,if there's a welch plug remove it, there's small holes in there, get a rebuild kit with new gasket if think you need it.,


I read from a technician before, that the spark line boot won't have a problem if the contact is not that tight because of the high voltage or something. So I thought it would be the same for the distributor. I will work on the distributor first, clean, sanding, especially the rotor-carbon contact point, to see if it helps.

Thanks. BTW, the carb I think was cleaned very well. I did it the least 3 times thoroughly within this year.
 

GA_Boater

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That part of rotor was damaged when I tried to remove it from the trigger. But only that part was damaged long time ago and everything works good after that for a while.

The rotor and shaft are one piece and can't be separated. New goes for $350 (OEM) and $211 (CDI)

The distributor cap goes for $123.

Be careful with them.
 

isaacs

Petty Officer 2nd Class
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Oct 15, 2013
Messages
153
You need a new cap and rotor--don't waste your time trying to clean the old broken stuff; boats are known for eating up their own distributor caps. It looks like you broke the rotor by trying to pry it off of the metal plate; I suspect the plate and rotor are all one piece and should be pulled off together. The first time I did mine I had to pull REALLY hard, even though the engine was only a few years old--there was some rust on top of the distributor shaft sticking it to the plastic rotor. You may have to saw or break the plastic rotor in order to get it off--don't damage the shaft. A bit of grease on the shaft will prevent problems in the future.

If it turns out that your carburetor is giving you trouble despite having been cleaned it's probably been a victim of ethanol fuel and needs replacement. Stay away from ethanol--corn is good for eating and making booze, not for your engine!
 

isaacs

Petty Officer 2nd Class
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Oct 15, 2013
Messages
153
You need a new cap and rotor--don't waste your time trying to clean the old broken stuff; boats are known for eating up their own distributor caps. It looks like you broke the rotor by trying to pry it off of the metal plate; I suspect the plate and rotor are all one piece and should be pulled off together. The first time I did mine I had to pull REALLY hard, even though the engine was only a few years old--there was some rust on top of the distributor shaft sticking it to the plastic rotor. You may have to saw or break the plastic rotor in order to get it off--don't damage the shaft. A bit of grease on the shaft will prevent problems in the future.

If it turns out that your carburetor is giving you trouble despite having been cleaned it's probably been a victim of ethanol fuel and needs replacement. Stay away from ethanol--corn is good for eating and making booze, not for your engine!

Oops...sorry...just realized yours was an outboard. Probably a lot different from mine!
 

Chris1956

Supreme Mariner
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Mar 25, 2004
Messages
27,036
The dist cap and rotor are a bit corroded, however, I would clean them lightly with a fine sandpaper. Better to have them dirty, than broken, or worn away. Since you installed, or at least reinstalled a timing disk, maybe you put it in wrong, causing the timing to be off. The OEM timing disks used to have a stamped "up" on them to tell you which way they go in. Not sure what CDI has. My manual is long gone on that motor, so I cannot provide any further info on that.

The dist. cap also has a notch that fits on the trigger, if memory serves. There was some play in the fit. Have you checked the timing with a timing light (after setting the timing pointer)?

Finally, check the spark plug wires. Their resistance should be zero. The conductor should be stranded stainless wire. They can arc to ground, if the insulation is bad. Sometimes the spark plug end of them gets corroded. New boots and springs are cheap, and the wires can be cut down an inch or so, and still fit. New wires are avail on the web. Prices vary a lot.
 

racerone

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Dec 28, 2013
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I do not believe the rotor can be replaced.----It is all one part ?
 

CVX20SPRINT

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Sep 9, 2009
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213
A dirty dist cap was the biggest issue with my 73 1500 TOP when I brought it home.I picked it up at an OMC/BRP dealer where they had been trying to get it running right for a customer.They had been through the carbs,fuel pumps and fuel lines.New plugs also.When I got there they had pretty much given up on it.They told the cust and myself that they thought the reeds were shot.I did a complete lync and sync on it before I took it to the lake.It ran but not great.Back to the dock and pulled the cap.Cleaned the crap out of the cap and a way it went.Just had to adjust the carbs after that.Been good since 09.Pushed my 20 ft Carlson to just under 50 mph with an alum prop and no set-up at all.
 

GA_Boater

Honorary Moderator Emeritus
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49,038
I do not believe the rotor can be replaced.----It is all one part ?

One part as said earlier. Someone damaged the rotor thinking it is like 99.9% of rotors - Removable and it isn't.

rotorshaft.PNG
 

tavacska

Petty Officer 1st Class
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Jan 21, 2017
Messages
244
Thanks all for the good advices.

1. There is a touch point somewhere between the disk and the sensor, I can hear it when I install it. I guess it is the CDI product problem, because the gap is so so thin and there is always a touch point no matter what I do. But now I think there is still an option to fix that. I will find two thin washers to add to the two machine screws and enlarge the gap.
2. I installed and reinstalled the new trigger twice. The first one is from ebay that never used but dated to 1976. I always have doubts on that trigger because of the on and off of the sparks. But finally it's not it's fault, and fortunately I still keep it. The rotor flange was damaged at the first time but it still works like a charm for 4 months. So I guess the rotor is good still.
3. The disk was installed as CDI instruction. The rotor pointer should be aligned with right hand of the window. The spark timing is good. 5 degree for first pick up and 21 degree for max. 2 degree at idle position as before. But I do have to adjust the first pick up and max spark position. I guess it is because I changed the trigger, and it is changed more or less based on the new trigger.
4. I think the timing should be right. Because when I manually test the spark, I can always hear the spark happening at the specific degree. However, some times it happens at the spark tester, sometimes it happens inside the cap or the switch. Now I figure out that there must be some broke in the middle of the spark that makes it spark inside the cap.
5. Last night, I cleaned the cap, sanded the copper, and the rotor-carbon contact area. I am going to fix the disk-senor touch problem and then give it a try.

Fatwing Chris, thanks for your story, that's what I did in the last two months, spent quite some dollars to change innocent items. Hope it can run another 20 years.
 

Faztbullet

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Mar 2, 2008
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15,589
If you used the CDI trigger you must use their disk not your old one.
 

tavacska

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Jan 21, 2017
Messages
244
Hey, guys,

I have to update this problem.

It turns out to be the switch box problem. It can only spark for 1/8 inch. This is a new CDI electronic switch box. Who can imagine that it could be wrong?

Well, the thing is, my original switch box is defective, which can not spark at all. The new switch box can spark only 1/8. Is there something wrong that cause it to happen? Both switch box was taken on bench to have a serious test.

BTW, the new CDI switch's surface is bumping a lot, which I thought is common. And it turns out to be not.( you can see the bump in one of the pictures)


So I bought another new OEM switch box and a new auto coil, waiting for the delivery. And I also tried to return the defective switch box.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
I don't know if the auto coil is compatible with the Merc CDI ignition. A new aftermarket (Sierra) coil should be compatible and pretty cheap.
 

tavacska

Petty Officer 1st Class
Joined
Jan 21, 2017
Messages
244
I don't know if the auto coil is compatible with the Merc CDI ignition. A new aftermarket (Sierra) coil should be compatible and pretty cheap.
Seems a lot guy use auto coil and claims it has stronger sparks. I don't know. But I got mine in Auto Oreilly and the clerk says go ahead with your motor. I will works fine. Price doesn't differs a lot but I just choose the auto ones, who knows why I stick with it.

But anyway, now already changing a new OEM switch and a new auto coil, with the old distributor cap, the motor starts. But, it idles tough, and also uneven at >3000 rpm.


I say it tough and uneven, means the rpm jumps up and down in tachometer, 1200 - 1400 rpm idle in water tank. If I lower it to 900-1000 rpm, it will shut down when I gear it to forward. So right now, 1200 rpm for not engaged, 1000 rpm engage to forward. This is all the best I can get. But even like this, when I leave it running idle, it stops after 20 mins. The rpm keeps ranging from 1200-1400, sometimes maybe too low to have itself stopped. It does not sounds smooth. poo poo poo ... poo too too too poo poo....

I also tested the Hz between the two lines from the stator, it's a 12 pole. The number reads from 350 - 410 Hz. Jumping a lot.


At range to 3000 rpm with no engage, it still sounds a little bit uneven, but not that obvious though.


There are possible reasons for this.

1. Gas is about two month old. No water in it checked by naked eyes. But still may be the reasons of the uneven running.
2. Bad ignition. Maybe not. All of them 3/4 gap before put fuel gas in, very beautiful sparks. However, there still could be misfires.
3. Distributor Cap problem, probably. When manually rotate the wheel, there are sometimes misfires. Or it is just because it's not fast. Secondly, when I check the spark of #1, there is also lights for in-line spark tester of other spark plug.

So I think maybe it's the cap's fault again, but i don't how to diagnose it.
 
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