Its cold out and I saw a swap shop post for some 6ALs, got me thinking. Currently running MSD billet distributors with MSD Blaster Coils. Aside from getting a rev limiter, what other advantages would the swap give me? Could there be a performance gain? I have basically Merc HP500 clones. I feel like its likely more effort and cost than its worth. Carrying a spare coil around costs like $70 carrying around a spare 6AL is like $300.

Some may say otherwise but I think most would agree that they aren't worth the trouble especially with an NA setup.

MSD hasn't made a good unit in 20+ years. Not sure I'd even use one of their coils.

I've used MSD 6T's for years now. Hope I'm not jinxing myself but never had an issue with them. The "T's" are made for nascar or for off road and are epoxy filled so seawater/air and vibrations has no effect on them. Bought a couple off eBay over the years and found them dead. Shipped them off to MSD and they rebuild them for like $75. I figure being they are full of epoxy they just take the board out of your box and pop a new board and wires in and send it back after testing (they even send you the testing sheet).
Now I did this building from scratch and some pretty wound up motors. If you have a stock set up and it works there is not much gain from it.

I have MSD 6AL's, billet dist and blaster coils on both engs. In ~10 years, I've had one 6AL die. Sent it in for repair and it works fine again. I found another on Craigslist in another state. Guy shipped it to me. I sent it in to MSD for checkout and a new pig-tail. I forget what it cost but it was very reasonable..Now I have a refurbished spare that costs me abt $150 total.

From what I've gathered, the 6AL doesn't like being mounted to the eng. Too much heat/vibration?? Mine are mounted to the boat.

The MSD distributors have a very well earned reputation for rusting internally. When I opened mine (after running 2 seasons) found weights were rusted in the full adv position on one eng and almost there on the other eng.. One spring was gone and the other was barely hanging in there. Both cleaned-up well and new springs were added. Used some LPS rust inhibitor spray going back together. 8 years later, no more rust. Good idea to pop the cap off and look around once a year at least.

I like the idea of multi-spark but don't have any data to support performance gains.The MSD stuff was on the boat when I got it, so wouldn't know if there was any seat-of-the-pants difference or not switching from orig ign controller. The engs do start easily, hot or cold.

Ignition is a digital system: it's either working for that cycle or it isn't. Once the fire is lit, it's lit. No amount of extra sparks is going to help a fire that's already burning.

Problems arise when system energy is insufficient to light the charge. That can be from not enough insulation, cylinder pressure, fuel characteristics or fuel mixture. MSD systems help with the latter three, but are more taxing on the first.

Heres a interesting personal observation of mine on my dyno. I dyno ALOT of mpi stuff with the factory style distributor merc used, used various modules and various coils. When I use the msd adapter that lets you send the signal out to a 6 al box then back to the dual plug coil vs plugged in like normal,I have seen 3 to as much as 10/12 hp gain, talking low performance engines too only making 550/600/650 hp, nothing super exotic or with a bunch of compression. I have never tested a internal module msd 3 wire dist against a 2 wire or triggering a box with grey wire from the 3 wire in back to back test to see if theres any difference there on any low hp stuff.. I wouldnt run out and buy a msd box to add to a boat either unless on a modded mpi using the jumper harness where you can simply plug it back in stock when the box dies on the water. The blue marine msd boxes in my limited experience with them are the worst junk msd has made, I had 3 of them in a row with various defects and gave up on them.

It's been almost 20 years now that 155mm Artillery ammo has internal rocket guided GPS.

Shouldn't be too difficult to produce a good ignition box for marine.

MSD really failed here. That's ok, Daytona has picked up the slack.

Chineseium, im sure. Ive told the story of the 3 in a row bad MSD marine boxes several times on post on here but heres the condensed version:
My old MSD got bounced on concrete 6 feet falling off a ladder at another shop by one of there employees after dynoing and quit working
bought a MSD marine box, one would randomly cutout and cough in boat, not great for a blower engine, one of the replacements revved to a strange rpm and went on a rev limiter even with chip out, something like 3800 or so, 3rd box showed up DOA. At that point I bought a MSD tester, a very cheap, capable tool that is basically a signal generator and can be used to test virtually any box and even trigger some efi stuff without running a engine for diagnoses. So after rewiring all the stuff in boat and wasting all minds of time going to water to test and retest and NOT changing any of the issues, in 10 minutes I deemed each box clearly defective on bench. When tester was hooked to box that randomly coughed, i was dry firing it with tester and could tap on side of box w screw driver handle and make it do same thing on spark tester. Was NEVER wiring or install. Box 2 you cranked knob on tester, it hit 3800 or whatever , spark quit completely and that was that, no chip in it, all the tapping in world, whatever made no difference. Box 3 didnt spark at all, if you yanked or tugged hard on wiring going thru bulkhead, it would fire then quit. Called MSD with results, their tech line guy had NEVER heard of a MSD tester, started rambling about improper wiring, grounds, battery leads, buffering capacitors. Was hard to make him understand that I was BENCH testing it with their tool. Told him he might want the serial numbers off the boxes, he said those numbers meant nothing, calling tech lines is a waste of time. I really just wanted a a RMA to send them back.
Price of these has quadrupled since I bought mine: