EST Distributor

So here's a deep one...

When summarizing, I cleaned the rotor and cap on the distributor (2005, 5.7l Indmar). I noticed that the distributor shaft is pretty corroded where the rotor presses on to it. I mean...really corroded. So, I spend several hours Googling for replacement shafts. No luck.

So, next I start Googling for the whole distributor. That's where things got interesting. The marine EST distributor looks identical to the car "vortec" model. I absolutely can't tell the difference looking at the pics. The car distributor can be found for $69, while the marine is $300.

Anybody know what the difference is?? If there is some difference in the cap or such, can I swap the car shaft into the marine distributor?

What kind of corrosion are you talking about? Caked, rusted crap or a greenish or white powder on everything? Is this causing an issue with firing?

The shaft can be cleaned up pretty easily. Take a little carb cleaner or brakekleen on a toothbrush or something similar, remove the rotor and do a little bit of judicitious scrubbing. Take a shop rag and shield the backside of the distributor with your free hand to prevent crap from flying all over the engine. Then a few puffs with a little compressed air (again with the shop rag shielding the backside) to finish everything off. Repeat if necessary.

I have an MSD disttributor and about once a year I take the cap and rotor off and have to clean the inside of the distributor and the shaft all around the mag pickup. It gets a greenish powdery corrosion all over it like that.
Theory says the ionizing gases or ozone present in a distributor cap is highly corrosive and mated with the high speed spinning rotor, high voltage, resistance, capacitance, inductive reactance, electrolisys (and other high tech, electrical engineering specific terms) can be a perfect prescription for corrosion. Add in a damp atmoshere and/or vented corrosive gases from the engine oil sump (via the PCV or even the distributor shaft itself) and...well you know where this going.

Supposedly, venting the cap by drilling holes in it will prevent this but a marine distributor is vented and screened already to act as a flash arrestor. High performance auto buffs can drill holes in the cap without being screened but doing that in a marine environment can at some point in time bring new meaning to the term "big bang theory". I wouldn't recommend that.
The base of the distributor should have a screen or two in it that may have been corroded to the point it's plugged up and not venting as it should. If so, clean that out as I stated above. Maybe faulty or worn plug wires or spark plugs are causing excessive spark reactance in the cap magnifying the problem. Is the ignition module gap properly set from the pickups in the distributor shaft?

If it hasn't gotten to the point of causing misfires, clean it and makes sure the vent screen is clean and make sure the plugs and plug wires are all good. Verify the gap of the mag pickups from the module.

You should not have to be replacing the distributor because of this IMHO.