Spark plugs should be CHampion QL77JC4 plugs gaped at either .040 or .030 (original and revised recommended gap). One gap or the other may provide improved performance at full throttle or idle... it varies from engine to engine.
Pertaining to the spark jumping a 7/16" gap, I assume that you are saying that with the spark plugs removed, the spark jumps that 7/16" gap on "all" cylinders with a strong blue lightning like flame... a real SNAP? If so, that's fine. If anything else, let us know exactly what you mean.
Compression on that 1989 200hp model will generally run 95 psi on the starboard bank and 90 psi on the port bank... you're right in that ball park.
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Your engine is equipped with a 35 ampere stator, having a series of exposed coils to provide AC voltage to a water cooled voltage regulator/rectifier to provide charging power to the battery. There are also two large black coils at the rear portion of the stator that provides approximately 300 AC volts to the powerpack capacitor.
That 35 ampere stator runs extremely hot and those two large black coils will in time melt down, dripping a sticky looking substance down on the timer base and the powerpead area. This results in a voltage drop to the powerpack whihc in turn results in weak, erratic, and eventually no ignition/spark. Was this the condition your original stator was in when you inspected it?
The flywheel on that 35 ampere charging system has a series of magnets attached to the flywheel with epoxy. Those magnets are spaced evenly, approximately 3/8" apart. If any of the magnets have come loose and are touching each other, that will need to be corrected. Are "all" of the magnets secured properly?
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In cleaning the carburetors... did you make sure that the brass high speed jets that are located horizontally in the bottom center portion of the float chambers are absolutely clean and free of any debris that might be floating around?
The throttle butterflies (all) should just start to open when the scribe mark on the cam is aligned dead center with the throttle butterfly cam roller... not before or after.
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Replacing the timer base for the reason stated is understandable whether it was faulty or not.
I have no idea why the engine would be affected by the weather temperature other than a remote possible condensation problem which could cause a shorting problem in any exposed circuit... check the following.
(Electrical Pins/Sockets - Poor Connection)
(J. Reeves)
The electrical rubber connectors that house a series of Pins and Sockets within them have a flaw which can easily be overlooked. The the pin or socket (or both) has been known to be pushed back slightly when pulling them apart and pushing them back together when replacing a component or doing test work.
Also, the wire that is attached to these pins and sockets has been known to break away from the pins/sockets which results in either a very poor or no connection at all. I've found many instances where the wire is held tight in the rubber connector by pure friction but in reality is not making any connection.
Be sure to check all of those rubber plugs for the proper pin/socket position and wiring attachments.
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Let us know what you find.
