The old school HEI's that came in millions of passenger cars and trucks from 75 to the early 80's. In the 80's they started to come with CCC computer control. However the units before that had a vacuum and mechanical advance. You can drop one of these right in no problem. Since the carb has no vacuum you can bypass the vacuum advance and since boats are mostly used at mid to wide open throttle the mechanical advance is all you need.
I just converted my TBI truck over to a carb and I removed the computer control distributor and installed a standard HEI with vacuum and mechanical advance.