Jon,
Yes, you can replace your shielded aviation plugs with automotive style, Autolite 386 is one option. It will probably cost you $200-$300 to make the switch. I have several posts/threads that cover various aspects but I think the following thread is for you. Make sure to use copper core plug wires, carbon core resistor wires are for modern electronic ignition systems that make much higher voltage.
https://southernairboat.com/phpBB3/viewtopic.php?f=47&t=71145&p=685650#p685650
Pro's and con's are as follows:
Shielded AV plugs:
Cost a lot more ($300 for 12 is cheap, look for outdated stock on ebay etc.)
Last a lot longer
Don't foul nearly as bad
Don't interfere with electronics
Automotive unshielded plugs:
Cheap
Change every 25-50 hours
Pick heat range vs. fouling and/or cylinder temps
Interfere with electronics
Once you get into the mags themselves, this is a rabbit hole to go down.
https://southernairboat.com/phpBB3/viewtopic.php?p=700199#p700199
You also have the option of switching to airboat electronic ignition systems (~$1,500 USD) that eliminate the bads and keep the goods.
You are unlikely to run into the issues I have with pushing these engines at high continuous power, but one last thread to keep you busy through another sunless winter :thumbleft:
https://southernairboat.com/phpBB3/viewtopic.php?p=692858#p692858
My recommendation in your case, clean your shielded plugs and get the motor/boat up and running. You may have mag issues etc. etc. left to solve. Cost to replace the entire mag system with electronic is similar to rebuild of your mag system. Unless you know your mags are golden, spend the minimum on the ignition system until you know about the rest of the power plant.
