No question is dumb . . . except maybe "Where does the drain plug go?"
Ilmor and Indmar are companies that marinize engines for the boating industry. (It's amazing how many times "Indmar" is misspelled in boat ads -- Indamar, Inmar, Inmer, Indemar!" I think it originally stood for Industrial Marine.
For umpteen years MasterCraft used Indmar engines. They switched to Ilmor in 2011. Do a search here on TT and you'll find lots of discussion about it.
In times past, MC also used PCM (Pleasure Craft Marine) engines -- up until about 1987 or thereabouts.
Other boat manufacturers have used the same engines, but sometimes with different trade names, ex. Indmar Monsoon in the Malibu.
The engines have been/are your typical Detroit workhorses -- the Ford 302, the Ford 351W, the occasional (and seemingly rare) Chrysler, Chevy 350 (5.7l), Chevy 454, and now the newer Chev/Cadillac/GM hitech engines.