A Sprintmag is fairly comparable to a Vertex magneto except that it makes a little more current and voltage at the plug due to the external coil. You might notice a little power gain from recharging if the mag is way down on output. I'd be most concerned with reliability if you've not had anything done to it in that many years. Since mags generate ozone inside the cap, things can rust up pretty quickly depending on what climate you're in. Having it serviced every other year means it'll run its best and have plenty of poop. Your Sprintmag can be upgraded to a Sprintmag+ which makes about 3 amps (7 amps measured like a Pro-Mag) and that would have a rare earth magnet in it.
The best thing about the Sprintmag is that it's a "constant duty" mag. You can run it all day and it won't get too hot and hurt itself.
A Super-Mag IV would work great but they're bigger in diameter. Not sure if space is an issue. The power to drive them isn't going to be noticeably more than the Sprintmags. You probably wouldn't see a gain in HP for your application. A little nitro or a supercharger and you would. If you're drag racing, then a Super-Mag would be great for you. Anything bigger than a Super-Mag III gets too hot to run for a long time. Lake boats, hot rods or circle track guys need to stick with a Sprintmag or a Super-Mag II. A III will be ok if it's out in the breeze.
The good news is the lower drive for your Sprintmag will also work on any Super-Mag if you decided to go that route. The coil would work too. You'd just need the generator and be up and running.
For your application, I'd say the best mag is one that's "paid for"
If you plan improvements in the future that would require more mag, upgrading to a Super-Mag at some point would be a good plan. Until then, your Sprintmag oughta work great with a little love.
Spud
