Engine size is what will determine whether engine driven compressor is mounted to engine or boats structure. Compressor weight and dynamic torque loads when compressor clutch is engaged can damage undersized hardware fasteners on newer light weight engines like the 3 and 4 cyl Yanmar diesels. Eight years ago I was commissioned to assist mechanics for three bare boat charter companies to test and repair refrigeration on over 30 boats. All but maybe two I believe of these boats had engine driven holding plate refrigeration systems with compressors mounted to boat structure and not attached to engine. My own 32 Watkins with engine driven refrigeration system operated 28 years before I sold boat with compressor mounted to boat structure. For the first 6.5 years engine driven refrigeration was run every day for 26 weeks a year. The SD508 Compressor I installed in my boat was removed from a 1978 automobile and was still operating when I sold boat two years ago. At final survey the original cutlass bearing was still in good shape.

Mutable piston compressors like I sold and the newer Seafrost compressors when used in auto AC systems at greater than one ton do require tight belt tensioning that would misalign cutlass shaft bearings on boats with soft engine mounting. When this same compressor is used at low temperatures to freeze holdover plates of 10 gallons or less compressor load is normally ¼ to ½ horse power. The key to remote mounting refrigeration compressors is belt tension should not be tight enough to misalign crankshaft belt drive pulley. The key to 28 years of service on a single compressor is compressor drive pulley should be sized to keep compressor speed between 1200rpm and less than 1600 rpm, My Yanmar compressor drive pulleys were 4 inches in diameter when I was in this business.