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TOPIC: How do you handle corrosion in distributor cap contacts?

How do you handle corrosion in distributor cap contacts? 08 Jun 2017 23:22 #1

  • jmcajmca
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I find the contacts in my distributor cap getting corroded fairly rapidly. I warm up my engines every couple of weeks, and I find a layer of green corrosion on the contacts after a couple of months. I clean with contacts with a Dremel brush and the green corrosion comes right off. The engine starts and runs nicely with the distributor cap cleaned.

Have you faced the same problem and how do you solve it? Is it okay to coat the contact slightly with dielectric grease to prevent the corrosion?

Thanks,
Joe

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1986 2850 Commend Bridge
A260 and AQ280 with DP lower unit
San Francisco Bay Area
Purchase the boat in 2005

How do you handle corrosion in distributor cap contacts? 09 Jun 2017 02:54 #2

  • mister larry
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Before you start greasing the distributor contracts, try something else. Get a drop light and place it next to the distributor so you get a little heat on the unit.

Every once in a while we hear stories about folks that "warm the engine" up regularly, but really don't warm it up. When this happens water vapor and moisture in the crankcase (who knows where it comes from) rises up the distributor shaft. When the humid air reaches the distributor cap is collect there. When the cap cools down after the engine is shut off, the moisture condenses and reacts with the metal contacts.

Some external heat, like from a light bulb left on when ever the boat is in cool conditions, should prevent this condensation. I would guess you could turn the light off in a day or two after the moisture has found its way out of the distributor cap. Then, some day when you are working on the engine, pull the distributor and check/replace seals, bearings, bushings, etc.

FYI - the moisture in the crankcase completely evaporates when you have the boat out on the water and everything is really warmed up. Your problem usually appears only after short warm up cycles when things do not really get HOT for an extended period: enough time to totally dry out the crankcase.

Happy boating.

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How do you handle corrosion in distributor cap contacts? 09 Jun 2017 04:09 #3

  • builderdude
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Not sure I'd recommend leaving a lighted light bulb in the engine bay of a gasser, or any other boat for that matter. Sure it'll put off some heat but thats actually what may cause a bigger issue :whistle:

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How do you handle corrosion in distributor cap contacts? 09 Jun 2017 04:39 #4

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In general, either run your engine at speed for a half hour or more, or don't start it at all. Anything else simply invites condensation. See it all the time with customers cars. They start it and run it for 5-10 minutes to warmit up, every few weeks when not driving it, to "charge up" the battery / circulate the oil. All they really do is accelerate rust and corrosion.

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How do you handle corrosion in distributor cap contacts? 09 Jun 2017 06:21 #5

  • jmcajmca
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I have been running my engine on muff for about 15 minutes until it reaches operating temperature. Interesting that short runs will cause condensation. Instead of a light bulb in the engine room I can put a Golden Rod which some people use inside their gun vaults. In fact I have one inside the cabin running all the time.

Joe

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1986 2850 Commend Bridge
A260 and AQ280 with DP lower unit
San Francisco Bay Area
Purchase the boat in 2005

How do you handle corrosion in distributor cap contacts? 09 Jun 2017 18:03 #6

  • grey.wilfong
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A spritz of Water Displacement formula 40. it does exactly what it was designed to do. I spray a little in the cap and on the points, blast any excess off with air and its good to go.
Chevy 350's are notorious for not liking moisture, especially at the coil and distributor. The WD 40 helps keep the airborne moisture away.

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How do you handle corrosion in distributor cap contacts? 09 Jun 2017 20:44 #7

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grey.wilfong wrote: A spritz of Water Displacement formula 40. it does exactly what it was designed to do. I spray a little in the cap and on the points, blast any excess off with air and its good to go.
Chevy 350's are notorious for not liking moisture, especially at the coil and distributor. The WD 40 helps keep the airborne moisture away.


good quality caps and wires make a big difference in damp environments.... go with the best quality available (not always the most expensive) and it will minimize the problems..

and I agree that moisture can set down under the mounting plate and turn to vapor and condensate on inside the cap... remove the moisture and try to prevent moisture from getting in again..

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1989 Bayliner 2556, 5.7 OMC

How do you handle corrosion in distributor cap contacts? 11 Jun 2017 17:45 #8

  • mister larry
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Go ahead and try the Golden Rod. You are into the experiment NO $$ since you already own one.

As for WD 40, I have been told to not use it on anything electrical. Spray silicone does not conduct electricity. Although you are talking about 20,000 plus volts through this circuit, there could be a time when you need all the oomph you can get. WD 40 could impede that process. In addition, if the Golden Rod works you don't need to pop the distributor cap whenever you bring the boat back home.
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How do you handle corrosion in distributor cap contacts? 12 Jun 2017 05:26 #9

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Thanks for your responses. I have another thought: what about enclosing or wrapping the distributor in a plastic bag and put some descicant inside to absorb the moisture? That is a cheap and easy thing to test out.

Joe

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1986 2850 Commend Bridge
A260 and AQ280 with DP lower unit
San Francisco Bay Area
Purchase the boat in 2005

How do you handle corrosion in distributor cap contacts? 12 Jun 2017 13:14 #10

  • driz
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I just pop my cap every year or so and hit the dremel with the dremel and 1" stainless wire wheel . Every 5 or more years I toss on a new nap and rotor. Never an issue really but it does get really furry on the contacts.
Those wire dremel wheels are the cats meow . I buy them by the bag of 20 for about a buck apiece when I run out. Fantastic for cleaning corroded terminals in all my vehicles.

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How do you handle corrosion in distributor cap contacts? 13 Jun 2017 13:58 #11

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Wrapping the distributor in a plastic bag (with desiccant in there too) might work. I might ask that if you follow up on this experiment you keep us posted.

We now have two suggestions as to the source of the moisture: under the mounting plate, or up the distributor shaft from the crankcase. Your plastic bag will fix one but not the other.

For your sake I hope you don't need the bag because that results in one more task you need to perform before you can fire up the boat: removing the thing.

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How do you handle corrosion in distributor cap contacts? 16 Jun 2017 17:51 #12

  • desuch
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Heat lamp on engine year around its really does stop all moisture

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located in ketchikan ak,name DOMINION
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How do you handle corrosion in distributor cap contacts? 18 Jun 2017 19:57 #13

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jmcajmca wrote: I find the contacts in my distributor cap getting corroded fairly rapidly. I warm up my engines every couple of weeks, and I find a layer of green corrosion on the contacts after a couple of months. I clean with contacts with a Dremel brush and the green corrosion comes right off. The engine starts and runs nicely with the distributor cap cleaned.

Have you faced the same problem and how do you solve it? Is it okay to coat the contact slightly with dielectric grease to prevent the corrosion?

Thanks,
Joe


I get that on my 2452 (5.7 V8) all the flaming time. It maybe takes 4 to 5 months for the spitting to start. I just keep two caps, one perfect and one in use. I just cycle them when I start to get a misfire. I spray the inside of the cap with WD40 which reduces the propensity to grow green lumps on the contacts. I have a tiny file that I use to clean the freshly removed cap and prepare it to be my hot replacement. I am pretty sure that the wd40 is helping.

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Terry (Retired Diving Instructor and Part Time IT Consultant)
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How do you handle corrosion in distributor cap contacts? 18 Jun 2017 20:26 #14

  • Cool Beans
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Never had the problem with any gas engine I've owned in a boat. At least with the engines I've run, the distributors were sealed (ignition protected) so no moisture would build up. Are you running automotive gear or marine?

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. . .It places the lotion in the Basket. . .and that basket happens to be in a 1987 Bayliner 3870 w/ Hino 175's

How do you handle corrosion in distributor cap contacts? 19 Jun 2017 06:49 #15

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All of my parts are from marine sources. I don't remember what brand is the distributor cap. The cap came with a gasket but it is a little bit flimsy. Do you think three are differences in materials between auto and marine caps? Or may be there are difference between different brands of marine caps?

Joe

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1986 2850 Commend Bridge
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Purchase the boat in 2005

How do you handle corrosion in distributor cap contacts? 19 Jun 2017 12:42 #16

  • Cool Beans
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Materials difference? I'm not sure...if I recall correctly, automotive caps have a vent to atmosphere and no gasket/seal at the base while the marine versions have a gasket and no venting.

Of course, my automive experience is mostly with old fords and the marine stuff was sierra brand parts and most recent my atomic 4.

But even with my A4 sitting all winter in a sailboat engine box, it was only every couple years I'd hit the cap and rotor with emery cloth to knock off carbon...no green corrosion ever. My dads 5.7 never had any green corrosion either, and it spent years sitting....it still has a 7 year old set of cheap sierra cap and rotor on it.

Not sure if I missed it in a previous post, but you don't have water sitting in the bilge under the engine do you? Another common denominator mine and my dads boat had was they remained dry inside for the time they sat...

Just some suggestions. Good luck!
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. . .It places the lotion in the Basket. . .and that basket happens to be in a 1987 Bayliner 3870 w/ Hino 175's
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How do you handle corrosion in distributor cap contacts? 19 Jun 2017 21:53 #17

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My bilge is dry. I do have condensation on the top sides of my boat overnight due to the warm days and cold nights in my area. Now that I am in a covered berth, I hope things will get better. Depending on how fast is the corrosion in my new berth, I may still going to try a bag of desiccant. Thanks

Joe

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1986 2850 Commend Bridge
A260 and AQ280 with DP lower unit
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Purchase the boat in 2005

How do you handle corrosion in distributor cap contacts? 19 Jun 2017 23:04 #18

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You're welcome. I wish I had an answer for you. . .good luck and share what you find if you figure it out!

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. . .It places the lotion in the Basket. . .and that basket happens to be in a 1987 Bayliner 3870 w/ Hino 175's

How do you handle corrosion in distributor cap contacts? 19 Jun 2017 23:30 #19

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+1 on using only marine cap and rotor. The vent hole is for automotive engine application. Interestingly aircraft magneto caps are often gasketed and no vent. Some are actually pressurized to maintain air density at higher altitudes. Never had condensation problems with them. So probably best to use marine products as Cool Beans said.

Greg

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How do you handle corrosion in distributor cap contacts? 19 Jun 2017 23:47 #20

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I've been following this thread, looking to see if there is any new tricks for solving the corrosion issue. Recently i lost both engines on a trip with the family in some not very nice weather... I managed to get one engine started and limped to the anchorage, upon tearing things down looking for the problem I found alot of moisture in both distributor caps and badly corroded posts inside. I'm pretty sure my moisture issue was a result of me cleaning the engine room and not drying out things properly, If you havn't had any water in the bilge or havn't cleaned or hosed down anything recently I would bet your moisture is coming from inside the engine through the shaft. Some of that may be unavoidable but I would way rather put a magnetic oil pan heater on to keep things warm rather than starting the engine frequently. You will never get it warm enough to burn of the moisture accumulated during the short run. Maybe something like a fogging oil would give you some peace of mind when leaving the boat for longer periods ? I've been thinking of doing that myself .

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How do you handle corrosion in distributor cap contacts? 20 Jun 2017 00:05 #21

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Mercruiser distributor caps are vented, there is a 90 degree plastic elbow that threads into the lower side pointed strait down. Both my original and replacement caps have this.
Never seen a vented cap on any old school domestic automotive engines

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Dave
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How do you handle corrosion in distributor cap contacts? 20 Jun 2017 00:26 #22

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my 1987 F250 had the last year available of the carb'd version of the 460. it had a vent on the cap. I think my 68 mustang does as well (289). Though, it could be a manufacturers thing? For the Mercruiser cap and it's 90 degree vent, is there a vented system it should be hooked up too? open air venting to the engine compartment violates the ignition protection standard required by the coasties I think. . .

Ford 460 cap. the black bump is a vent:

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. . .It places the lotion in the Basket. . .and that basket happens to be in a 1987 Bayliner 3870 w/ Hino 175's

How do you handle corrosion in distributor cap contacts? 20 Jun 2017 01:59 #23

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Replacement cap from West marine. No venting system, not sure why, just know it is :whistle:

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Dave
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How do you handle corrosion in distributor cap contacts? 20 Jun 2017 16:01 #24

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Dave is correct.
Many older Mercruiser distributor caps are vented...that is a safety vent, ignition protected, but to allow ventilation.

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How do you handle corrosion in distributor cap contacts? 20 Jun 2017 16:14 #25

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Be sure to use a thin gasket between the cap and distributor cap, should be supplied with a marine cap.

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