Suggestions for a 1978 TOP 900 coil

[Rstacy]

I have a 1978 TOP 900 serial #4848720.
I have owned it for about two years. Top end power is very good. The carbs were cleaned before I got it.
The idle has always been rough and has been steadily getting worse. Last night it actually bogged during acceleration. It only did it once but ran strong after that..except for the idle.
When I got home I did a compression test. All 6 cylinders are at 125 pounds give or take a pound. When I removed the spark plugs I noticed that all of the plugs were wet with oil.
Fuel filter in the pump is clean. Squeezing the fuel bulb while running has no impact.
Searching has suggested the coil as being weak. There are many options for coils. Ranging from $25.00 to $180.00.
Is there a favorite coil manufacturer that is built strong to last long?

 

[jimmbo]

Can the spark jump a 7/16" gap? On every plug wire? Are the carbs dribbling gas out of the vents when running? Are they all fully closed when at idle? Are the mixture screws all set for best idle. "Carbs cleaned before I got it" could mean last week or 5 yrs ago. I know what I call 'cleaning a carb' and it is not spraying SeaFoam into the throat. What ratio are you mixing the oil? The Spec is TCW-3 @ 50:1
Mercury still sell coils. The Mercury coils are well made, the current one might be over 40 yrs old, and there are lots that are older. I would be leery of the Cheaper ones. Mercury did select a less than great product when it came to most of the wire used on those engines. The Insulation has not aged well in most cases

My first Merc was a 78 900

 

[Faztbullet]

That is a battery CD ignition so coil output increases as battery voltage rises from charging system. It sounds like wet fouling from possible bleed restrictors missing. When missing the fuel puddles in transfer port and when you "hammer down" the puddle is drawn into cylinder, then the raw fuel fouls the plug for a millisecond or so causing bog till its burnt off.

 

[Rstacy]

So kind of strange but here it is.
I bought an aftermarket coil and it would barely run. I installed the old coil and it started right up.
The plugs that were in the engine were two seasons old. I cant tell you how many hours but our seasons are pretty short here. For lack of something better to do with my $20 I went ahead and replaced the plugs.
It was night and day on the water. Just like that the problem was solved. It ran all day. We will see what the next trip out brings.