I have a new to me boat with twin 1983 Crusadar's 7.4L 350HP. I would like some advise on upgrading the Champion rv8c spark plugs. I don't want to change them again for a long, long time. Any suggestions? I will call Crusadar Monday for their advise, however I like starting here because no one is trying to sale me anything...lol
You don't say why you're changing the plugs or what you want to accomplish.
If the engines are in good condition, whatever is the stock plug is probably right. If the engines are oil burners, a hotter plug. Running a hot plug for no reason can cause piston & valve damage, and not very much extra power. If you are looking for economy, put in diesels.
I purchased the boat from a marina selling boats in default of storage fee's. I wanted to install new plugs so that I would have a date to write in the maintenance log; a new log since the boat did not come with one. When I pulled the plugs I noticed they are Champions. I thought Champion plugs were cheapest plugs out there.
Plugs are not that expensive and I really don't want to change them out again for sometime. That's why I wanted advise/info on a better plug.