Mercury Outboard Ignition Coil Testing 1967-1988 L3's, L4's, & L6's

Quick Video on the evolution of Merc Inline Ignition Coils (1967-1988) and how to perform a resistance test. 3 Different types discussed: 1967-1978, 1976-1978, and 1979-1988 (L3's, L4's, & L6's). Specs for the Primary Output for coils 1967-1978 and 1976-1978 are .1 - .2 (R x 1 = .01-.02). Secondary Output 5700-7300 (R x 100 = 57-73). Specs for the Primary Output for coils 1979-1988 (ADI Ignition) = .2 - .4 (R x 1 = .02 - .04) **Note: I have had success with coils reading .2 - 1K. Secondary Output = 800-1100 (R x 100 8-11). Always check for chips or cracks in your Ferrite under the rubber. This is can cause/lead to arcing. Hopefully this video helps with diagnosing your engine. Any questions or comments feel free to reach out anytime and as always, thanks for watching!!!

[@BornAgainBoating]

Man you are on point with the old Merc's! That's awesome keep up the great work! We just did a video this week repowering a 34 Venture with Mercury 300 Verados. It won't upload until later today, but we never see older outboards like this! You've got an cool thing going here!

[@robertpayton3795]

Glad to see you are again on the tutorials. As always the information is on point. Season is coming up soon.

[@colsmith7257]

Great work as usual, a tidy workshop speaks volumes.

[@mcleodhomeservices]

Great tips. Been looking for a YT expert on Merc’s. Think I’ve finally found him! 👍🏼

[@bouldernelsonbigfoot]

Can't hardly hear you. You have best ,easiest to follow and understand video's on KZbin . I have a hearing issue ,lmao. Thanks

[@MerCSonL6]

I'm poor lol. Sorry my production is horrible..... in this video I'm literally working out of my kitchen. Son

[@stephenvaldez328]

Important! Correction! OEM Mercury Coil Thunderbolt Ignition Models & Some Others (Coil Off Engine) Secondary Circut Test With Positive Lead To Coil Tower Is Correct, However; The Negative Test Lead Does NOT Go On The Negative Post, But On The Thin Braided Bare Negative Wire 'Pigtail' There Will Be No Reading (OL) Otherwise & You'll Assume Incorrectly They're Bad.. You Can Verify With SELOC Manual 1406 1965-1989 Page 5-52 IGNITION 1970 thru 1979

[@swblack1216]

I watch a lot of your videos one quick question,best way to screw in compression tester in bottom cylinder?is There trick?

[@jeffquaiff3627]

your video's are great , they have helped me a lot ! I got all new coils and put them in but one not right ,one new one reads 250 the other two older ones read 940 . is it a defect or wrong size

[@MerCSonL6]

Defect. Son

[@jonathansumerfield8899]

I have a 2003 25 hp ELH Merc. The top and bottome cylinder coils across the terminals both read 0.1, and the negative terminal to the plug wire - top 995, bottom 963. The top cylinder seems to run fine, but the bottom cylinder fouls the plug. I switched plugs and the same result top good bottom fouled. Both cylinders have good compression at 105 psi. I was told that it's a carburetor problem, but there is only one carburetor, so how could it work fine on one cylinder and not the other. Any suggestions would be greatly appreciated. Thanks, Jon

[@halspeed12]

If the stator is showing no ohms on the high side can that cause coils to go bad and motor run rough above about 1/2 throttle?

[@ksb552]

on the charging circuit red wire from wiring harness to rectifier then does a short red wire go to the live side of the starter solenoid need some guidance thanks by the way great tutorial

[@CrownVictoriaNightGhostVic]

Hi what do you think happens when putting in gear forward or backwards I hear grinding is it bad cables or something else thank you.

[@MerCSonL6]

Sounds like a loose/bad cable. Just to be sure I would disconnect the shift cable at the engine and try to shift it manually. It should "pop" into forward and reverse because the shift cam is spring loaded. Hope this helps. Let me know. Son

[@billblevins3581]

Hey Son, I have a 1988 Merc L6 and the coils have little aluminum tabs connected to the negative posts on the coils. The other end of the tabs are tucked into a slot on the side of the coils. Does the change anything with test procedures in this video?

[@MerCSonL6]

It does not.

[@FAAN910]

Hey Son!!! Brand new to boat engines. Love your videos. I have an 85 Mercury 850. If a coil is bad, do I have to go with what the recommendations are, or can I just use anything within the hp range?

[@MerCSonL6]

Coils should measure 8k -11k ohms resistance from input to coild tower. Coils doesn't go bad too often but I have seen in happen. Son

[@FAAN910]

@@MerCSonL6 appreciate the reply.

[@caribbeanpwc3550]

thanks for the video, my 88 Merc 100hp would not go over 2800 rpm this weekend, then it opened up and worked great, then later on it did the same thing after shutting it down for a little while. Any ideas on where to start? (It kinda seems like the bottom 2 cylinder where not getting spark) have you experienced these symptoms?

[@MerCSonL6]

I would test the spark with a gap tester. Should be able to jump 5/16 of an inch if my memory serves me well...... which is rarely does lol. Fuel is also top of the food chain when it comes to ignition issues. Hopefully this helps. Son

[@caribbeanpwc3550]

@@MerCSonL6 thanks!!! will do.

[@mikelutrell2832]

Are you still available for questions? I have a 1989 Merc 100 HP that has 4 c0ils like the ones in your video. I cannot get the plug wires out of the coils like they are made into them. when I put a probe into the tower and to the primary wire, I get zero ohms. when I put test probe into coil and other lead at plug end I get 0.5, 1.5, 0.5, and 0.2 for lead ohms . THANK YOU FOR YOUR VIDEOS AND YOUR REPLY! Mike

[@MerCSonL6]

The coils are almost indestructible. Perhaps the issue is deeper. Son

[@mrcamaro615]

How can you tell what year you have I know mine is a 115hp l6 with ADI Ignition

[@Matt-kg6kn]

Hey man, you got a lot of knowledge on these old mercs! That’s awesome ! My dad has a 68 650 Thunderbolt I’m trying to restore. But I’m stumped on the ignition system that’s In it. I don’t see a rectifier or stator? Is there models that didn’t come with them? Thanks In advance . If questions aren’t allowed my apologies and pleas delete

[@MerCSonL6]

The stator is fitted directly under the flywheel and some of the rectifiers are mounted on the starboard side on the lower cowling next the internal wiring harness. 650 is one of my favorite engines. There's only a 2 cubic inch difference on the block vs the later 1973 850. Good luck my friend. Son

[@brodylinde8534]

Wondering if your still here I have a 650 l3 tested the coil and the post reads all 0.00 would it be bad since it’s not the .1 to .2? The other test was good at 665

[@andyoleary2230]

That's some great information thanks! I am wondering where would I go to buy a brand-new early 67 orange 332-2983 coil?

[@MerCSonL6]

Ebay or maxrules. Son

[@raymondchavez1530]

Hi Son. Having a hard time finding the orange coil that comes from with 67-74. Can I use the 75-77 coil and mount it in there with some modifications?

[@MerCSonL6]

I have orange coils for sale on ebay. MerCSonL6 is my username. Other coils will not work due to the differential with resistance. Son

[@ScotchStraight]

Where can i find the info for 85 90hp 6 cyl coils and wires?

[@locknload9143]

Thanks for the video. Do you have your meter on 2k ? Thanks

[@MerCSonL6]

I honestly do not Remember....sorry lol.

[@locknload9143]

@@MerCSonL6 ...Drugs are Baaad! Ok thanks.

[@MerCSonL6]

@@locknload9143 lol, I made the video 3 years ago. I apologize my memory is as sustainable as it used to be. I'm not on drugs my friend. Just getting old. Son

[@locknload9143]

@@MerCSonL6 ...Lol yeah I hear yea brother.

[@garyjohnson4462]

I love your video's, but I don't know what setting on the omhs meter to put it on to check the coil. Thanks, We really appreciate your videos

[@MerCSonL6]

The "horseshoe"

[@adrianomedeiros3963]

I have a question. Well, a story and then a question... I bought a friend's 1987 Mariner 150HP to put on my boat. I fished with him in his boat using that engine til a year ago. We stop fishing and he didn't start the engine for about 6 months. Then, about 6 months ago he tried to start the engine but he inverted the battery cables. Never started the engine again. I bought it and was able to find a blown fuse and some disconnect wires and now I'm able to turn the engine from the ignition switch. I sprayed fresh gasoline with 2 stroke oil in the carburetors (and a little engine start on my second attempt) with no success. Battery was fully charged and the engine turned fast, but didn't start. I checked the 6 spark plugs for spark and I could see spark in all of them. What should I check next? Thanks!

[@MerCSonL6]

Compression. Engine only needs 3 things to run: compression, fuel, & spark. Let me know. Son

[@lyleschaubel2474]

I have a 1967 950ss and the coil is testing bad but i can't find one anywhere. Do you know of anywhere to get one or if i can upgrade it?

[@MerCSonL6]

That's a tough one to find. I'm not sure if a large orange one would work to swap out. They came out after the one you have. I have some if want to try. Lmk

[@jamesmercer7124]

IV got a1980 70hp triple. And I'm having problems with starting. Compression is good and carbs are clean. I'm getting spark but I dont feel its hot enough, it blue spark but very fine and thin almost hard to see. Do you have any suggestions. Thanks for the time and helpful videos.

[@MerCSonL6]

Could be a faulty switch box, trigger, or stator. I would start with the switch. It's the cheapest. Coils seldom go bad. You may need a DVA to fully test everything if you prefer to go that route. Let me know. Son.

[@rdeanlive]

Hello the 1976 to 1978 looks like the one off of my 402. I need two coils and would like to ask you, would Sierra 18-5186 would be a match for these coils. Any info would be appreciated thank you.

[@MerCSonL6]

I don't know part numbers unfortunately. Too many to remember. The coil you have listed should work. The range on it 6-225hp. Hope this helps. Son

[@chachi5975]

@@MerCSonL6 I just ordered new 18-5186 and they measured to be 440 ohms. All 6 are consistent so I doubt a defect, what would you recommend?

[@johnjaromack9530]

Greetings Son, and your videos have really been saving my bacon. Thanks for doing what you do, sir. Can you tell me what you see when you look inside the earliest (332-2983) coil? Someone gave me a boat with a Mercury 850 (SN: 3740147), and the coil, when I look inside of it, is literally empty. I expected to see a screw terminal like the ones in the distributor cap, but all I’ve got is a hole that’s about 1-13/16” deep. Thanks sir, and keep up the great work. John

[@MerCSonL6]

Please rephrase the question. I'm not 100% sure what you are referring to. Thanks. Son

[@rdeanlive]

Hello would you have a stop switch for a 1973- 1977 mercury 402 elect. Stop switch part # 84-63086A2 as the one that was in there had orange wire to switch box.Any info would be appreciated thank you so much.

[@MerCSonL6]

Unfortunately I do not. Check marineengine.com

[@williammenta6875]

Will CDI coil work for replacement on 1976 115 hp model 1150?

[@MerCSonL6]

What type of cdi?

[@danielochoa9454]

Can I use the second style coil and “upgrade” my older style coil? I currently have the first original design

[@MerCSonL6]

The resistance is different. It will not work unfortunately. Son

[@pedelpopper]

hey im testing a 1971 coil and i cant seem to get a reading from the negative wen testing the secondary. but if put my negative lead from my volt meter on the small ground wire coming out of the coil i can get a reading. does this mean my coil is bad? sorry very new to this

[@MerCSonL6]

Yes. Son

[@pedelpopper]

Thank you for fast reply! Wish u all thr best

[@justindavis376]

Where can I find one or these older coils. Or can a modern one be retrofit

[@MerCSonL6]

What coil are you looking for? They all have different resistance readings.

[@paulkolenbrander6201]

I have a 1965 L6 tiger dual points. Can you help me with any tuneup information?

[@MerCSonL6]

The points need to be properly gapped and cleaned. I have several tigers I'm neglecting atm. Son

[@tompaa8212]

Hi son my magnets is cracked in my coils are the worthless? 1984 90hp cant´t see primary ign timing only full 21 degrees BTDC don´t know what primary should be? Tower of Power ohm reading on all six around 950ohm/0.2 and spark on all six but have a issue where it stops when put in gear sounds like a funny car, found a leak between fuel pump and block still whaiting for new gaskets hope this is the problem?

[@MerCSonL6]

Replace the coil. Son

[@mikehughes9884]

I have a 90hp mariner and have lost spark on the middle cylinder do you think the coil is to blame ? The engine still starts but only firing on top and bottom cylinder

[@MerCSonL6]

3 cylinder engine? Or 6?

[@terrywilson1813]

I have a mercury 90 2 stroke I use for fishing and it runs fine at first but after starting up and running 3 or 4 times for only a few minutes at a time it gets to where it doesn't want to start and when it finally does it stalls when I put it into gear....over and over again. Again it runs fine when I first get on the water just not after the engine is good and warm. It's usually a pain to get started too so is this a bad ignition coil? I'd greatly appreciate any input or advice

[@tylercarroll6949]

I’m having the same problem with my 90hp 2 stroke mercury what year is yours ?

[@terrywilson1813]

@@tylercarroll6949 mines an 83 but I figured out the problem was flooding. I cleaned the carbs and now use a different method to get it cold started it doesn't have any problems running now

[@mayolormairez2527]

Can I switch this coil out for an msd coil?

[@RABERTRON]

That test seems ok for my 79 70HP . How do I test the SPARK?

[@MerCSonL6]

Gap tester. Should be bright blue and easily jump 5/16th of an inch. Yellow or red sparks indicates a weak ignition system. Son

[@o4rudeboy]

do you work on forces? i have an 85 85hp i need help with

[@MerCSonL6]

Sure don't. However, they are similar to Mercury's. What's your issue?

[@JamesMcClure-dr9xx]

I have a 1982 mercury 115...wont plane out....checked timing, spark, ohms on stator within range....rebuilt fuel pump and carbs, checking coils now....thinking reeds or trigger at this point if coils check out?

[@JamesMcClure-dr9xx]

Coils, timing check out. Runs great bench testing with muffs. Losing all power under load. Nothing has changed lower unit wise since problem began. Can't get over 4000 rpm and takes about 5 minutes to plain out. Everything ignition side is within spec. Any help at all would be amazing. Thank you

[@MerCSonL6]

Check your fuel from the tank pickup all the way into the carbs.

[@JamesMcClure-dr9xx]

@MerCSonL6 i appreciate the help....well after breaking it down to crankshaft to inspect reeds...found a break in the wire coming of stator terminal running to idle stabilizer unit. Would have never found it without taking the control plate off though to get to intake bolts. Keep in mind if stator and fuel check out

[@southernsouperman]

What if the primary drops all the way to 0.00?

[@gilfredooquendo9969]

On what number should you set the multi meter

[@MerCSonL6]

My meter does not have numbers. It has am ohms setting. Saves time. Son

[@johannemasson1]

Can you rebuild the firs coil that you tested

[@MerCSonL6]

Negative.

[@timcrowe5706]

Question - any chance you know where I can source a replacement coil for a 69 Thunderbolt 500 50hp? Serial #332-2983. I’m finding the internet is being less helpful than usual… Appreciated.

[@MerCSonL6]

Is it a distributor ignition or energizer?

[@MerCSonL6]

I may be getting my ignition systems mixed. They used different types during 69 depending on the hp. I believe I have a 69 50 in my inventory. Pretty sure it's distributor with the big orange coil.

[@timcrowe5706]

That’s the one I’m looking for - exactly like the one you tested in this video.

[@jcoish30]

The coil 1967 - 1970 orange coil should be getting .2omes for the first test and 3 - 3.6 omes x100 for the second test.

[@danielochoa9454]

I tested my secondary output it’s reading 330 ohms does that mean it’s bad? I have the first style coil. The big one! And could I just install a different style one like the second one toy tested?

[@MerCSonL6]

I believe it's bad. And the other coils have different resistances. Not sure they would work for your application. I do have several of the large coils if you need. Lmk.

[@danielochoa9454]

@@MerCSonL6 hi thanks I do need another coil how much for one of yours?

[@MerCSonL6]

@@danielochoa9454 $30 plus Ship. Lmk. Son

[@danielochoa9454]

@@MerCSonL6 I want it you got PayPal?

[@danielochoa9454]

How can I get ahold of you? What’s your number

[@williammenta6875]

Can I test a switch box on a 76-77 115 hp mercury, will crank, no spark

[@MerCSonL6]

kzbin.info/www/bejne/kH_LoGuCls93erc

[@kylewoodward7078]

I have I believe a 89 45hp classic 50 mercury. You would basically do the test the same way? I been having a miss at full throttle. Changed plugs and did seafoam treatment..no better.. ran it yesterday, full tank of gas, switched to a different tank, when I did that motor started right up but now it won't accelerate no faster than idle speed, in reverse or foward, like the motor won't rev up. I'm thinking stator, because it starts and idles GREAT. Any advice appreciated man..thanks

[@MerCSonL6]

The test will work for your Coils. However, I would test your switchbox output to the coils with a dva peak meter. The switch needs to produce at least 150 volts to fire a coil. On average I've seen around 200v. This will at least tell you if the switch and stator are doing their job. If all tests pass then your issue is fuel delivery related (carbs/fuelpump/fuellines). Hope this helps. Let me know. Son

[@kylewoodward7078]

@@MerCSonL6 thanks for the reply. I found a broken throttle plate. I also did a ohm reading on the stator. The book says r x 1000 or 5.7 to 8.0 scale reading. ( kind of confusing) but I got 2.23 ohms resistance. I have read it should be around 5700 to 8000 ohm. So I guess the 2.23 would be x 1000 which would not be between 5700 to 8000. I think my high side of the stator is bad. Does that sound right to you?? Thanks for any advice!

[@MerCSonL6]

@@kylewoodward7078 resistance should be 5.7-8.0 between the blue and blue/white stator leads. 2.23 is low. I will tell you from personal experience that I've had stators fail resistance test and run perfectly fine. I would certainly check the voltage going from the switch to the Coils. Again, should be around 150v to 250v. That will rule out the more expensive electrical components. Let me know. Son

[@kylewoodward7078]

@@MerCSonL6 well I got the motor running, back to where it had the miss at full throttle, ordered a dva adapter should be here Friday. As far as the ohm test for the coils, should I take the coil packs off or is it ok to do it on the motor.? My motor is the 45hp classic 50 88 I believe, is that the last year they made the 45hp classic 50??

[@MerCSonL6]

@@kylewoodward7078 I believe 89 was the last year of the classic 50. I would remove the coils for the test. The positive n negative terminals have to be disconnected for the test. Dva will tell you at minimal if your stator and switch are doing their job. Let me know. Son

[@chrisambrose8838]

What would make my ‘78 1150 cut off and on while taking off under a load?.

[@MerCSonL6]

There's a 100 things that could cause this issue. Does it idle fine?

[@chrisambrose8838]

MerCSon L6 yes it idles fine... if you accelerate slowly it’s ok... if you jab the throttle, just it comes up on step, it cuts in and out?... thank you for the reply!

[@MerCSonL6]

@@chrisambrose8838 no worries my friend. Try turning all 3 carb idle screws out (ccw) 1/4 turn. If it falls flat again, then do another 1/4 turn ccw. Son

[@MerCSonL6]

Engines not getting enough fuel through the idle circuit. That's what it sounds like to me.... i have been wrong many times b4 tho. 😇

[@chrisambrose8838]

MerCSon L6 thank you ! I will try that and let you know !

[@drieslaas8664]

Son, I desperately need advice on a perplexing issue I am having, with 1995 Merc 30hp strokes. Is there a way I can contact you in private please?

[@MerCSonL6]

What's your issue? Can you summarize it? Let me know. Son

[@drieslaas8664]

@@MerCSonL6 Cool thanks for getting back to me. I solved part of the issue, and have one motor starting easily, running sweetly and, under no load at least, not showing any sign of bad behaviour. The other motor is progressing backwards. I rebuilt the carb, and I am sure it is completely clean. I cleaned filters, replaced fuel lines from the tank, washed the tanks properly and ensured that the fuel is fresh and clean. The motor ran for a few seconds, then stoppped running, and then started making some dreadful grinding noises. I am sure it is metal on metal contact, and I am thinking I will need to pull off the powerhead and dig deeper to find the issue. Would you mind if I asked for advice from time to time, I am not a great mechanic and will have to rely on all the help I can get. My position in Zululand, South Africa makes it a little more complex when it comes to phoning a friend....

[@MerCSonL6]

@@drieslaas8664 Sure. For what's it worth I'll help you in anyway I can. Son

[@drieslaas8664]

@@MerCSonL6 I found that the flywheel is loose on the crankshaft. I have not been able to get the nut off yet, but it seems that the key sheared off. Spinning the crank with a spanner (with plug out to remove compression,) the motor seems to turn freely, so I do not understand why the flywheel would shear off in the first place. Anyway, I have to find a way to get the upper nut off. I was thinking of just taking an impact wrench to it and knocking against the inertia of the drivetrain. Otherwise I will probably need to drop the lower unit and hold onto the propshaft somewhere lower. Can you think of a reason the flywheel would shear off, even if the engine seems to turn freely?

[@MerCSonL6]

@@drieslaas8664 the flywheel nut wasn't properly installed or the flywheel wasn't lined up when torqued down.

[@josewales892]

Are you still available for questions?

[@MerCSonL6]

Sure. What's up?

[@josewales892]

@@MerCSonL6 thanks for the reply but I found the issue to be in the switchbox rather than the coil. Thank you anyway! ✌

[@rdeanlive]

Hello I have a 1977 402 mercury that has no spark. Installed a open coil CDI stator as the old one burnt out, changed the fly wheel; trigger oms seemed o.k. still no spark. Went and picked up another old used control box and still no spark, now getting mad as hell by now.Went on the computer and watched your video and thought to myself ah ha I bet it could be the coils. I changed all the old wiring that all frayed in this motor too.The coil readings on the secondary were very low a lot of cracks and ferrite under the rubbers they both need to be replaced.Well this is what I wanted to ask you. I could go to the marine store and maybe pickup to very used coils.Started to search and they don't show any after market that would fit this model.They are same as you had on your bench.Any info would be helpful sorry for rambling on so long. wife won't listen, thank you for your time. Ray

[@MerCSonL6]

You can find your coils on Ebay or marineengine.com for around $15 bucks if my memory serves me well. Wives never listen. You are not alone my friend. Son

[@jamesmercer7124]

Sorry forgot to add when it does decide to start there is no rhyme or reason why. It might start, then I shut it off then it wont start until IT wants too