What exactly are the differences? Is it just a waterproof issue, or a spark issue like in starters and alt.? If just a waterproof issue, then I take it this will not be a conscern with Mr. Coast Gaurd?
(MSD & Crane systems)
Also

What is the deciding factor of going to the 8.5mm plug wires over 8.0mm?

Thanks
Jerry

With the ignition module it is waterprofing but with the distributer it is an ignition ( spark ) issue.
The bigger plug wires offer more insulation but with the water jacketed headers you don't really need the bigger wires just good ones.

Thanks Buddy!

Going to use my Merc distrib either way, just didn't know about the boxes. So the wire sizing has more to do with heat insulation. 8.0mm it is then.
Jerry

US1.........MSD has the Heli-Core for about $50, #3123 in blue with a 90degree boot that are excellent. (In fact I am gonna put 2sets on mine next weekend). The also include a good cutting block/crimper for almost goof-proof cut-to-length. These are 8mm.

A Pt #.......cool, thanks. I've looked at them thru Summit and there must be a 100 different chioces. gives me a headache. I only want 2 choices......red or blue.

PS
My motor is only a V-8, so I think I'll just order 1 set.

I like the TAYLOR spiral core wires -have used them for years and had no problems.

You said that you were going to use the merc dist. either way. Are you using it in place of your merc. ignition box or wired in after the merc box? The stock merc ignition curve is built into the box not the dist.like on the older cars. If you dont plan on using an ignition box with the curve inside than you have to use the aftermarket box between the stock box and the coil. There should be instructions hopw to do this or ask the manufacturer.

Going to keep my stock Merc distrib. vs buying an MSD distrib.

Yes, I'm aware that the aftermarket igniton boxes will replace my stock ignition module.

NO NO NO the aftermarket box WILL NOT replace your stock ignition module unless you buy one that has an ignition curve built in. If it doesn't you have to install it downstream of the stock module. The stock merc. distributor doesn't have any spark advance built into it. The advance is built into the module.

The Crane marine unit does have a built in adjustable curve advance, in addition to a built in rev limit.

So if I go with MSD, I still need my module for the curve? Did not realize that.

Sounds like Crane is the way to go.
Thanks

US1Fountain. FYI.......The reason I picked the 3123's (and you have to tell them you want the blue ones...for example), is that you cut these to length. My guess is if you were to order the ones for a BBC they would be too short because of the header systems on the marine applications. (and it does come with both types of dist caps, regular and hei).

Bob