adding power to 86 ski nautique

The GT40 heads and the Edelbrock intake are good upgrades but I've been unable to find an HEI distributor that fits a 351W that is approved for marine use. I experimented with an automotive HEI on my 88 Ski Centurion w/Indmar 351W. Even after getting the advance curve right, the engine still backfired through the carb and just wouldn't run right. Part throttle and mid range power were good, but when I got down on it hard, after about a minute or so, it would lose power and snort and pop through the carb. If you can find a marine HEI for your application, I'd say try it, otherwise don't waist your money. I went back to my Prestolite distributor w/Pertronix solid state ignitor. If you want to beef up your ignition, I'd go with a marine MSD unit and Blaster 3 coil. This will do away with your ballast resistor and boost your primary coil voltage up to about 200 volts. You'll be able to increase your plug gap to the .050 - .060" range. If you're going to take this route though, I'd highly recommend going with a premium set of 8mm plug wires and get a wire separator kit to keep your plug wires separated.

I have not seen a MSD marine distributor for a 351W, only Mallory, are you sure about the MSD marine, I've seen 351 C not W.

If you're looking for a marine HEI distributor for a 351W check out:

http://www.performancedistributors.com

I've got one for my '79 SN 351W. It's a little spendy ($375 for the standard unit and $450 for RH rotation) but worth every penny in my opinion. I've used it for two season's and it's been great. They custom tune the advance curve to your engine specs.

As for intake manifolds be careful to watch your height. I have an Edelbrock Performer intake and I had to get a 1" shorter flame arrestor to get my motor cover to close completely. I know Edelbrock makes some other intakes that are quite a bit taller than the Performer