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1981 Mercury 90HP OB Spark Problems

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astroglass_81

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"Hello, I am new to this site

"Hello, I am new to this site and find information here very informative. I just aquired an 1981 Astroglass 15' 6" Fish & Ski, with a 1981 Mercury 90 HP Outboard. I really don't know anything about the history of this vessel, and have never heard motor run, but does not look too bad. With that said, Compression on 3 cyls is 135, 2 cyls 132, other cylinder 128. Drained grease out of foot (no water-yipee!), replaced water pump impeller and checked spark on all cylinders. All cyls were good at 1/4" gap except #5-dead. Swapped (+) coil wires between #5 & #6. #5 coil then fired, #6 didn't. Is the switchbox dead on that cyl only? and I also found ground screw connection loose for #5 coil. Would that have caused switchbox to fail on that cyl? I know very little about outboards, but have been an auto mechanic for years. I have never heard this motor run. Has been sitting atleast a couple years. Just removed gas tank, going to clean crud out of bottom and install a new sender. Then going through carbs, fuel lines, and maybe fuel pump, (gas very stale) Any help would be appreciated. Thanks"
 
Post your serial number I have

Post your serial number I have some books that can help but need to know the year of the engine. Also does it have a distributor or coil packs x6 ??
 
"Information From Mercury: 198

"Information From Mercury: 1980 Mercury 90 HP O/B
Model: 1090620 90ELPTO Made In Canada
Serial: 7179095 Date Of Purchase 09/18/1981

According to Seloc Manual, I think it has a CD Ignition System. (Coil per cyl w/ 2 switchboxes)

All cyls fire except #5. I noticed I also need to remove the stator and install new wires on it to the rectifier, insulation cracked off and wire decayed. But at that, I don't think that has anything to do with just 1 dead cyl fire. Also in need an opinion on the type of fuel sender that works best, arm or reed. My tank has no baffles and is maybe a 10 or 12 gal permanant mount plastic tank. Thanks for all the info."
 
"I forgot to ask about stator

"I forgot to ask about stator and trigger removal/reinstall. Is that a major task, and I'm assuming engine would have to be retimed? My thoughts are maybe removing the stator and installing new wires (soldering? or new harness if possible?) on stator to correct the decayed wire problem."
 
"No retiming the engine is nee

"No retiming the engine is needed, but the plastic timing pointer will need to be reset with the spark plug dial indicator.

The stator is well known for going bad, taking out the switch box with it. Don't worry about decaying stator wiring. That whole thing gets thrown away. That has nothing to do with the problem. The charge windings go bad. The tiny trigger wires breaking off can be fixed."
 
"Hey Bandit..Just 1 cyl (o

"Hey Bandit..Just 1 cyl (on top box which is for #5 cyl) is bad. I'm guessing that that 1 complete switchbox will have to be replaced to correct that problem. The frayed wire I was refering to I'm assuming is coming from the stator (wire hooks to rectifier). I don't know if the stator is charging or not, because I have not as of yet had the engine running. I thought rather than blowing the bucks on another stator, if I could put wires on this one (if this stator was good, just bad rectifier wires) then it would work. I was thinking that the reason the switchbox quit on that cyl, is the ground terminal was loose on #5 coil. What did you mean by spark plug dial indicator?"
 
"Ignore the yellow rectifer le

"Ignore the yellow rectifer leads for now. Don't do the sw.boxes yet. You need to get this thing running on 5 the way it is first. Check out the stator fully. If the engine will not run right over 2000RPM or starts dropping other cylinders that do the stator first. That is what causes the sw boxes to fail. A loose groung will do that as well. 90% of the time the stator spiking everthing is where the problem begins with these.
I do not recommend replacing on sw. box on any 6 cylinder. It will kill the other, than it self within 3 months."
 
"astro the switch box is proba

"astro the switch box is probably your problem. check the other switch box that is good with a ohm meter and be sure it is 10k to 13k ohms if so it is fine to replace one box. The terminal i am talking about is the bias circuit white with black stripe check that terminal to ground on the case.. I use liquid tape on some of the wires that are brittle and frayed, usually the wire itself is ok."
 
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