Many of those engines were installed in a lazarette. Dont know if the spelling is correct on that one. Anyway a lazarette is basically an engine bay. No transom mount. As such, the exhaust fumes from the engine were "less than desirable" from the sailing crowd so a plug was installed forcing the exhaust to exit down and away from the enclosed area the engine ran it. When unplugged the exhaust was up in the cocpit of the sailboat. That wreaked absolute havoc with the typical sailboater who hated outboards with a passion anyway.
Back then OMC even made what was called a Sail Drive. A 35hp powerhead with basically no midsection. They were installed in sailboats as a main power unit. They were installed on a mount system that basically looked like a huge donut. Vibration free.