The M3-20B is the engine that should drop in.
here's the specs The Universal M3-20B, 20 hp, 3 cylinder engine with the standard reduction gear of 2.05:1 costs $5873.00 - good thru March of 2003 View the M3-20B specifications at http://www.marinedieseldirect.com/unispecsheets/m320b.pdf (requires Adobe Acrobat Reader) -Standard engine features include- Self-Bleeding Fuel System Adjustable Failsafe Flexible Mounts Fresh Water Cooling w/ Heat Exchanger Coolant Recovery Tank 12 Volt Electric Fuel Transfer Pump Electric System 12 Volt Electric System, Negative Ground Glowplug Cold Starting Aid Control Brackets - Throttle/Stop and Shift Low Oil Pressure Alarm High Water Temperature Alarm Pre-Wired Engine Lube Oil Drain Hose Air Intake Silencer Owner's Manual and Parts List The "Admiral" panel, with tachometer, hour meter, oil pressure gauge, water temp gauge, engine pre-heat and key switch is $387.00
here's the specs The Universal M3-20B, 20 hp, 3 cylinder engine with the standard reduction gear of 2.05:1 costs $5873.00 - good thru March of 2003 View the M3-20B specifications at http://www.marinedieseldirect.com/unispecsheets/m320b.pdf (requires Adobe Acrobat Reader) -Standard engine features include- Self-Bleeding Fuel System Adjustable Failsafe Flexible Mounts Fresh Water Cooling w/ Heat Exchanger Coolant Recovery Tank 12 Volt Electric Fuel Transfer Pump Electric System 12 Volt Electric System, Negative Ground Glowplug Cold Starting Aid Control Brackets - Throttle/Stop and Shift Low Oil Pressure Alarm High Water Temperature Alarm Pre-Wired Engine Lube Oil Drain Hose Air Intake Silencer Owner's Manual and Parts List The "Admiral" panel, with tachometer, hour meter, oil pressure gauge, water temp gauge, engine pre-heat and key switch is $387.00