I'm assuming you meant to say how many? The majory of I O's (inboard/outboard) are all GM manufactured The main one's are MerCruiser, Volvo Penta, Marine Power and Pleasurecraft Marine( not all GM) A quote, The marine engine makers buy basic GM assemblies called long blocks, which contain the engine block, cylinder heads, crankshaft and pistons. Then they are fitted out with ignition-protected electrical components, as well as raw-water cooling and water-cooled and wetted exhaust systems. The blocks are also reinforced to better withstand the prolonged, heavy use common to marine engines. All the mercruisers, V 8's/V6's/inline 4's are GM which makes up a HUGE part of the marine industry.
As for reliability, it burns me say that these things are so d@mn reliable, if they were anymore I'd be jobless.You gotta give credit where creditis do.....(I guess). The big issues with boats returning for service usually have to do with water in the feul type of things.
Hope this answered your questions. Let me know if they didn't. I get confused easily.
