My answer to Cruising (offshore sailing): Should I get an inboard or an outboard motor?
Answer by Desmond Last:
Unless you want to put out an SOS you will need an inboard. An outboard will spend most of its time in the air. Unless you have a Yacht such as the Top Hat 25′, which has a well in the cockpit into which the outboard will fit, then the outboard will have to be fitted to the stern of your yacht – the transom.
When there is a large swell and/or very bad weather the stern of your yacht will be traveling anything up to a third of its length above the water. With it will be your outboard with its engine over revving as the propellor spins in mid air. It will happen to an inboard as well but nowhere near as bad. It is very difficult to repair an outboard if it breaks down in a storm.
The inboard will also have a better charging system and the ability to run a compressor for your fridge system.
Maintenance For Inboard: You will need to maintain the stern gland. This is where the propeller shaft runs through the hull of your yacht to the propeller. Modern Yachts have self adjusting and self lubricating stern glands. Older yachts will have a stern gland that will need to be replaced at regular intervals and either greased or adjusted so a small amount of salt water lubricates the gland packing and the shaft.
If it has a leg check the water intakes, anodes and make sure the sealing bellows is not showing signs of hardening as it will split.
Tip: It is a good idea to check gearbox and engine alignment this stops excessive wear on the shaft bearing.
Fuel: Most Inboards are diesel. Drain the water from the fuel system at regular intervals.. Make sure your fuel filters have glass bowls with drain taps. Diesel will absorb water and allow an organic growth to block your system.
Xtra Life Saving Tip. If you are going to sea drain and clean out your fuel tank and replace your fuel filters.
Cooling System. I once spent an offshore voyage in the Engine room in a 30–40 knot gale. The Engine was overheating and I was the mechanic on board. It was not nice.If your engine is saltwater cooled replace the water pump impeller every 12 months. Check the exhaust manifold at the start of every season. Change the anodes every 12 months.
For fresh water cooled engines flush out the heat exchanger at least every 2 years. Change the anodes every 12 months.
Alternators on boat engines have a hard time. Make sure the fan belt is tight.
Life Saving Tip: Never use a car alternator on a boat engine. Use a marine alternator as they are spark suppressed.
Make sure your batteries have a solar panel or wind generator to keep them charged up. Ensure your house batteries and Engine batteries can be charged separately.Make sure they are secure.
Fix any oil leak immediately – it is a fire hazard.
I would recommend that you have the engine serviced every 12 months regardless of use.
An outboard is ideal as a backup but offshore an inboard is much safer and practical.
Tip of Tips. Never buy a boat without an out of water survey and engine inspection by a marine professional.