Aircraft and boats have a few things in common:
1. If the Donkey (engine ) stops chances are you will be in trouble.
2. There is no hard shoulder.
3. There will be no garage in walking distance to pick up fuel (or oil) if you run out, or a service engineer to call on.
Second hand engines? dont do it!
Buy new every time, only this way are you sure of how the engine has been treated.
You will be in control of your destiny to a much greater extent.
Remember: the sea takes no prisoners!