Logo
Get instant online access to repair manuals for your Mercury / Mariner outboard. Online Manuals
MercuryMariner
Order printed Mercury / Mariner service manuals — shipped to your door! Printed Manuals
MercuryMariner
Use engine diagrams to find & order parts for your Mercury / Mariner engine. Engine Diagrams
MercuryMariner
Find parts quickly with Mercury application guides. Quick Parts Guide
MercurySierraCDI
Results 1 to 26 of 26
  1. #1

    Default Mercury outboard.

    Hello all, I have been given an old Mercury outboard which I intend to use with my old rowing boat but I cannot get it to start. There is no spark, I have taken the flywheel off and there are magnets set into the flywheel and a coil. There are no contact points but there is an advance/retard lever. The coils check out ok. They have continuity. If I spin the flywheel what voltage should the magnet/coil generate as I am only getting millivolts. The magnets are not weak. It is a very old engine but not as old as myself as I stopped counting at 80 and at a guess I would say about 2 to 4 hp and is a two stroke. Thanking you all for your help in advance.

  2. #2
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    16,923

    Default Re: Mercury outboard.

    Need more info: how many cylinders, any model info on the cowling?

    It takes a DVA meter to accurate judge the system.

    Jeff

  3. #3
    Join Date
    May 2007
    Posts
    9,267

    Default Re: Mercury outboard.

    The ignition coil produces AC so as Jeff notes you need a (direct voltage adapter) to convert it to DC so it can be measured accurately.

    If it has good continuity (very low resistance) between the two leads then the windings are "probably" sound and the issue lies elsewhere.
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  4. #4
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    Sure there are no points hidden in there somewhere? Then it can't be TOO old. If it's black with white/silver highlight, then it's a 39 or 40.....single cylinder 4 hp. Lower unit may be shot. See what the oil in there looks like. I have 6 of them here....all needing lower units. Driveshafts rusted on these, then water gets in at seal just below the water pump. Serial # will begin with a 1 or a 2. In early 70's they went with red highlighting.
    Last edited by timguy; 08-08-2020 at 02:03 AM. Reason: Add info.

  5. #5

    Default Re: Mercury outboard.

    Quote Originally Posted by timguy View Post
    Sure there are no points hidden in there somewhere? Then it can't be TOO old. If it's black with white/silver highlight, then it's a 39 or 40.....single cylinder 4 hp. Lower unit may be shot. See what the oil in there looks like. I have 6 of them here....all needing lower units. Driveshafts rusted on these, then water gets in at seal just below the water pump. Serial # will begin with a 1 or a 2. In early 70's they went with red highlighting.
    Hello, Thank you for the reply. The cover is black with gold/yellow stripes and the number 6490442 is stamped on a plate. I think that it is a 3.5 as I can just about read the faded lettering. There are no points or capacitor. The coil under the flywheel for generating the voltage has two wires, one goes to the engine body and the other goes to the ignition coil. The other terminal on the ignition coil also goes to the engine body. This would have been the wire that I would have expected to go to a set of points and capacitor. I do understand how ignition systems work but as I am not up on boat engines I am surprised that there is no points. I have another scrap engine of the same model and it is wired the same. It has now become a challenge to get the engine running so I am most grateful for your thoughts. William.

  6. #6
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    Wow that is pretty new motor....late 80's. Different ball game. No points of course. Do you have a multimeter? Better yet can you borrow a DVA meter? Why? This would measure peak pulses as the coil under the flywheel produces AC current. That is collected in a capacitor discharge box (called a switch box for Mercury motors and a power pack for Evinrude and Johnson motors). This charge is then triggered at the precise time by a another pick up under the flywheel which is advanced timing when you want to go faster. Going back to the switch box it fires a lower voltage then into the final spark coil which amplifies the voltage to maybe 30,000 volts for your spark. Very simple......right? You have 4 components that can fail and 2 of them without any notice. Maybe you should sell those and work in something with points, condenser, and 1 coil......all turning on a simple stator plate that advances when you're ready to go faster. How about a 1972 Evinrude 6 horsepower? If you want to challenge your mind and open up the wallet, you can fix it. We will walk you through testing proceedures....they are fairly simple.
    Last edited by timguy; 08-08-2020 at 10:38 AM. Reason: Typo

  7. #7

    Default Re: Mercury outboard.

    Quote Originally Posted by timguy View Post
    Wow that is pretty new motor....late 80's. Different ball game. No points of course. Do you have a multimeter? Better yet can you borrow a DVA meter? Why? This would measure peak pulses as the coil under the flywheel produces AC current. That is collected in a capacitor discharge box (called a switch box for Mercury motors and a power pack for Evinrude and Johnson motors). This charge is then triggered at the precise time by a another pick up under the flywheel which is advanced timing when you want to go faster. Going back to the switch box it fires a lower voltage then into the final spark coil which amplifies the voltage to maybe 30,000 volts for your spark. Very simple......right? You have 4 components that can fail and 2 of them without any notice. Maybe you should sell those and work in something with points, condenser, and 1 coil......all turning on a simple stator plate that advances when you're ready to go faster. How about a 1972 Evinrude 6 horsepower? If you want to challenge your mind and open up the wallet, you can fix it. We will walk you through testing proceedures....they are fairly simple.
    Hello and thank you for your reply. There is no capacitor discharge box and there is nothing under the flywheel apart from one coil which the magnet skims past. I have another engine of the same model and it is exactly the same. William.

  8. #8
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    Does it look like this?Click image for larger version. 

Name:	Screenshot_20200808-151329.jpg 
Views:	11 
Size:	136.2 KB 
ID:	24497

  9. #9

    Default Re: Mercury outboard.

    Hello, Thank you for sticking with it, no it is not like the pic. There is a plate which moves from side to side and the coil is fixed to that. When the plate is moved it alters the position of the coil and also connect to the carburettor. I would say this is the throttle. Something like advance /retard. This is under the flywheel. There is nothing else. Is there any way to send you pictures if so keep it simple as I am not good with computers and thank you again. William.

  10. #10
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    Snap a picture and downsize to under 1000k. Then in your next post, hit go advanced. Then hit little paper clip up in icon line above your text. Follow prompts to add the photo. Then your downsized photo, which can be found in your photo folder or file, it will be available to click on. I use "lit photo".....works great.....download that app....I will send you a link.

  11. #11
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    Here, see if this is clickable, then you can download this app and fix photos to marineengine size. It will create its own folder for your modified pictures.....I love this app. litphoto.
    https://images.app.goo.gl/uHFviBdqruVYg97P6
    The number you have on the motor seems to come through properly as a 3.5 or 4 horse.
    Does this look like it?
    Don't think that coil/module is available new. Try Tim's Outboard in Hackensack MN 218 682 2331. Talk with Teresa, Mike, or Dan......might have to leave a message. Tell em Tim sent ya. Leave your serial number. Might consider a new impeller too.
    I'm working on a record perhaps.....I intend to keep repairing outboards until I'm 90 years old....now at 64, already got 55 years in, repaired a 10 horse Merc in 1966 and sold in the Duluth newspaper for $150. Big money for a 10 year old.....in 1966. My Dad was so frustrated with the motor after hauling it back from remote Ontario, cleaning fuel tank and carb.....then testing it on a little local lake near Hibbing MN. As it refused to start, his wrist watch broke off and flew into the root beer water. We were out in the middle of the lake, but rowing distance to the landing. He looked up at the landing, and down at the motor, then at the white skin on his arm where the watch used to be.......he started loosening the motor clamps...... tears welled up in my eyes.....I begged him to stop. He had the motor ready to drop when I cried out "Please Dad....don't do that please please". He looked down at me and smiled....."think you can fix it.....it's yours". My Dad was my hero......true story. Started fixing outboards and never looked back.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Screenshot_20200808-210732.jpg 
Views:	6 
Size:	149.3 KB 
ID:	24503  
    Last edited by timguy; 08-08-2020 at 10:35 PM. Reason: Add info./ Typo/add picture.

  12. #12

    Default Re: Mercury outboard.

    Hello, I have taken photos. went to advanced and then the paper clip but when i try to do anything the computer will not allow it and informs me the site is not safe, most annoying. I have only ever sent photos. to someones email address and have never had any problems doing that. Over the past years i have always spent Christmas in South Carolina as my partner lives there but this year due to the virus I will have to stay here as the USA will not let me in. My partner cannot get here either. She spends 6 months in the summer here. I send her photos. regularly and we also talk and see each other on skype. William.

  13. #13

    Default Re: Mercury outboard.

    Hello, On the cowling it says 3.5. It has one cylinder. The ignition system consists of a magnet set into the flywheel which spins past a coil which is mounted on a plate which moves when you move the lever. This is also connected to the carburettor. Throttle. This coil is connected to the ignition coil. There are NO contact breaker points and no capacitor. Is it relying on the pulse from the magnet/coil to generate a spark and if so how powerful have the magnets got to be. Do they lose it over the years.The ignition coil is ok as I can get a good spark the the plug if I use a battery. The coil under the flywheel is 216 ohms. which is what i would expect. I have another engine of the same model but a basket case and it is wired the same. I have not come across an engine like this as all the small engines that i have seen always have points and capacitor. I welcome your thoughts on this. William.

  14. #14
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    Does it look like my last attached image?

  15. #15

    Default Re: Mercury outboard.

    Hello / Yes I would say that is the one as I cannot see points or capacitor. Well done you really are the person to talk to. Do tell me how it works without the points/capacitor Now for the bad news. William

  16. #16
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    William, looks like that part not available. These will fail, I replace these self contained units on chain saws, little tillers and weedwhackers quite often. I will help you search for one if the unit from your parts motor is no good either. They are simple but fail in time.

  17. #17

    Default Re: Mercury outboard.

    Quote Originally Posted by timguy View Post
    William, looks like that part not available. These will fail, I replace these self contained units on chain saws, little tillers and weedwhackers quite often. I will help you search for one if the unit from your parts motor is no good either. They are simple but fail in time.
    Hello again. I think that we are going to put the unit aside and see if we can obtain another better on. As this is an island full of boating people we should be able to get an engine / I would be most grateful if you could explain to me how these engines work to generate a spark as they have no points to interrupt the supply. William.

  18. #18
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    When the magnet goes by the spark module/coil, it produces enough voltage for a decent arc in AC.....that is directed, in some cases, to a final amplifying coil. The main coil itself moves when you turn throttle, advancing and regarding spark as needed. No moving parts like points are needed. Just one unit is used like in this chain saw. In a chain saw there is no timing change....it's fixed timing.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	IMG_20200809_193513649_compress34.jpg 
Views:	4 
Size:	313.0 KB 
ID:	24509  
    Last edited by timguy; 08-09-2020 at 08:37 PM. Reason: Add photo

  19. #19

    Default Re: Mercury outboard.

    Hello, Thank you for the info. it is more than I have got from anybody here, they all have boats but no idea how they work. What you describe is what I have, a coil activated by a magnet and a second coil connected to the plug. As most ignition systems that I have seen have an interrupter such as a set of points or an electronic system and that this one seems to have none my question is this, is the magnet activated coil just a coil or is there something inside which senses voltage and acts as an interrupter. This for me is a learning curve. William.

  20. #20
    Join Date
    May 2020
    Location
    Stokesdale NC
    Posts
    314

    Default Re: Mercury outboard.

    A set of breaker points are just a timing device. The magnet at the flywheel produces a voltage in the coil which is timed by it's fixed position in relation to the crankshaft and therefore to the piston. The coil attached to the spark plug takes that voltage pulse and boosts it up to a voltage high enough to fire the plug.

  21. #21
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    Right. Now if you have no spark in your motor, William, You need to check compression first to see if it's worth spending money on coil/coils. Also check gearcase to see how grease looks first.....are you working on a saltwater motor? Just did this little Yamaha from Miami and had to change out the motor block. Why? It was completely eaten up inside by saltwater residue.....and kept trying to overheat. I took off the water jacket cover over the head and started to cry. The previous owner said he rinsed it out after every trip religiously. Wouldn't trust that guy as far as I could throw him.......all 300 pounds!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	13425_compress73.jpg 
Views:	3 
Size:	166.5 KB 
ID:	24520  
    Last edited by timguy; 08-10-2020 at 01:37 PM. Reason: Add photo

  22. #22

    Default Re: Mercury outboard.

    Hello, Thank you for the info. I am certainly learning and that is no bad thing. William.

  23. #23

    Default Re: Mercury outboard.

    Hello, Yes it is saltwater, We are only a few miles from the sea in any direction / We have no rivers. I took the cylinder head off the basket case engine and the water jack is packed solid with salt. The same goes for the bottom part of the outboard the other engine is much better. We have put feelers out to try for another engine. There must be many about on the island in sheds etc. William

  24. #24
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    William, what size and brand you want? I'll send you one. Got everything from a 1.75 Gamefisher (Force), to a 150 Black Max. All 4 sale. What are you looking for, a project motor?

  25. #25

    Default Re: Mercury outboard.

    [QUOTE=timguy;693222]William, what size and brand you want? I'll send you one. Got everything from a 1.75 Gamefisher (Force), to a 150 Black Max. All 4 sale. What are you looking for, a project mot Hello again, Thank you for all the info. as i have learned so much. We have now sourced another engine, Good health and happiness to you and yours, William.

  26. #26
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    3,186

    Default Re: Mercury outboard.

    What did you find? Need any advice or help, don't forget us, eh? Won't let us go to our camps in Ontario, so I'm spending more time on the forum.
    Last edited by timguy; 08-17-2020 at 03:08 PM. Reason: Typo

Similar Threads

  1. Replies: 2
    Last Post: 08-31-2015, 01:33 PM
  2. Mercury Outboard
    By Wild Card in forum Identifying Model / Year / Horsepower
    Replies: 2
    Last Post: 11-30-2011, 05:59 AM
  3. Replies: 7
    Last Post: 08-15-2011, 03:48 PM
  4. trouble starting 1971 mercury outboard mercury 650
    By noahsark in forum Mercury Mariner Outboard Forum
    Replies: 11
    Last Post: 09-24-2010, 10:07 AM
  5. 1975 85hp mercury mercury outboard
    By keithy6 in forum Mercury Mariner Outboard Archive
    Replies: 2
    Last Post: 07-25-2008, 09:09 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •