Weird Merc 2cyl 20HP blue band *thing*

[Mr-d]

Okay, i think the gremlins got our outboard.<br /><br />It all started out of the blue (yes, it's a blue stripe)After a nice evening out cruising my brother parked the boat, in full working order.<br />The next day, it refused to start, and occasionally backfired. So, we took the carb to bits, cleaned it (it was leaking fuel) and it was full of icky icky stuff, put the thing back together (it had not been used for a while) and still nothing, swapped the spark plugs, and Wow, it ran!!! but it now runs at about 15 knots max, whereas it did about 20 before (Lame spark plugs, lawnmower type.)<br />SO, after using it for a week now, i decided to try the old sparkplugs again and it fired up fine... however it is only running on 1 cylinder (we measured the spark plugs, perma gap thing and appeared fine)as soon as you open the throttle fully (WOT) it makes a weird jumpy sound/feeling and the 2nd cylinder engages and then stops, so we started messing with the fuel adjustment (it's 1.5 turns open now)<br />and i can now get it to run on 2 cylinders at WOT, but not at lower throttle. <br /><br />Sometimes, the 2nd cylinder makes a run for it and scares me, making the boat jump forwards sooo much faster than normal, it is dangerous.<br /><br />So, after a lecture of my dad (and a few backfires) i stuck the lawnmower plugs back in, and its running on 2 cylinders *Normally* again, but far far less power than the perma gap things.<br /><br />My question, WTH causes this, why does it backfire and why does it only run on 1.2 cylinders most of the time (with the original plugs) and 2 cylinders with the lawnmower plugs?<br /><br />Also, to add to this frenzy, "what year is my engine from?" <br />S/N 9205082<br /><br />Thank you

 

[emckelvy]

Re: Weird Merc 2cyl 20HP blue band *thing*

DO NOT run it anymore with lawnmower plugs!!!! You have no idea of what the heat range of those plugs is, and you may burn up your motor by doing so.<br /><br />Most likely reason it'll run on standard-gap plugs and not on surface gap plugs is that it requires more energy to spark a surface gap plug. <br /><br />I had a problem similar to that on a motor I worked on, and it turned out to have a bad (cracked) coil. The crack was such that, when developing a full voltage charge in order to fire the surface gap plug, the spark would be lost thru the crack, to ground.<br /><br />Now, with a standard plug, it didn't take as much voltage to fire the plug, and the spark jumped the gap of the plug much easier than it was able to jump the crack in the coil.<br /><br />One thing you could do would be to swap coils and see if the problem follows to the other cylinder.<br /><br />While the coils are out, inspect them all over for cracks and arc marks. It'll be pretty obvious if one is bad.<br /><br />One of your surface gap plugs might be bad, too, it'd serve you well to replace both of them. Maybe when the motor's running fast it makes enough power to spark the plugs, who knows. <br /><br />You may need to check/clean/regap the points under the flywheel, 1973 models (which is what you motor would seem to be) may or may not have points ign (according to my book they don't, but just in case.......).<br /><br />If you have a 'black box' mounted somewhere on the side of the motor, you won't have points but will have a trigger assy and a charge coil under the flywheel. These items can be resistance-checked to make sure they're OK. Unfortunately it's quite hard to properly test the CDI unit (black box) without special equipment.<br /><br />If you have a externally-mounted black box, it could be going bad; it's not uncommon to see them cause intermittent problems like you're experiencing.<br /><br />Be sure to check all wiring connections for tightness, internal breaks, and corrosion.<br /><br />Here's a good link to wiring diagrams and other good info for your motor:<br /><br /> http://www.maxrules.com/wireindex.html <br /><br />HTH and G'luck.

 

[Mr-d]

Re: Weird Merc 2cyl 20HP blue band *thing*

We checked the coils, they appear fine.<br /><br />It does have a black box thing on the side so it cant be the points? <br /><br />when we swap the coils over the problem remains, swap the sparkplugs the problem remains.<br /><br />The lawnmower plugs appear to be running it fine, the cooling water is nice and cool, and the plugs are just as cold to touch as the perma gap things after running.<br /><br />The wiring appears to be excellent all round.<br /><br />Now that you mention it, one of the coils does produce a weaker spark..<br /><br />What does a pair of new coils cost, and where can i order them? (Im in the UK)<br /><br />If i try to look at mercury's part express, i cant find ANYTHING on my outboard, it's like it does not exist.<br /><br />Thanks you so much

 

[JFNStuart]

Re: Weird Merc 2cyl 20HP blue band *thing*

Mr-D<br /><br />I too have a 20HP Merc from 1980/1<br /><br />You will not be able to find anything on Mercury parts Express, probably because the engine is too old but if you need to find part numbers I would use :<br /><br /> HTTP://WWW.MERCRUISERPARTS.COM <br />This site will let you search for parts with pictures once you have chosen your make/model/year etc from the serial number. <br /><br />I think that your engine is a 1978 model but I could be wrong!<br /><br />To get hold of parts you could try:<br /><br />www.keypart.com<br /><br />I would phone them rather than use the email system as they don't seem to reply by that. <br /><br />they are based down south in the UK and seem to have a good stock of parts. I would think that a new set of coils would be too expensive, so you may be better off looking for something second hand. <br /><br />Do you have the Seloc manual for the engine? This is reasonable for fault diagnosis. <br /><br /><br />Cheers<br /><br /><br />Stuart

 

[Mr-d]

Re: Weird Merc 2cyl 20HP blue band *thing*

Hi Stuart, thanks for your reply.<br /><br />Im off to take part with a Regatta/funday tomorrow, taking the boat along so i hope all goes well, or we will have a Mercury Anchor <br /><br />It seems to be starting to run on the 2nd cilinder earlier and earlier, perhaps all it needs is a good clean to brake up the carbon, we used Duckhams 2 stroke oil, and not the Quicksilver stuff, as we ran out, the duckhams seems to be lagging it a tiny bit, and under load small amounts of blueish smoke come out, so i guess its the oil getting burnt.<br /><br />I will look into getting that manual (if i can find it.)<br /><br />Do you have a remote set up on yours? If so, what type?<br /><br />Thanks,<br />Daniel.

 

[Merc805]

Re: Weird Merc 2cyl 20HP blue band *thing*

Your motor is a 1978 year. (Not that old) It should be a coilpack motor (No distributor).<br />200 (20,0) 9171006 - 1978 2 cyl <br /> http://www.myfishingpictures.com/watermark.php?file=527/141379merc.jpg <br /><br /> http://www.marinshopen.se <br /><br />You can check here for parts.. They are all still available.<br /> http://www.dougrussell.com/partscat...m?fuseaction=serials&colid=01&coldesc=200, 20