All engines need cooling and most car engines have a water filled radiator. On a boat, that hot water can be used to heat domestic water in a storeage cylinder via an indirect coil, and when that reaches the required temperature, the excess will be cooled via a tank welded to the boat keel.
The beauty of keel cooled engines as opposed to a wet exhaust cooled system is its all self contained and no raw water comes aboard and no weed can get stuck in filters. Most important in a muddy, weedy river or canal. This is called engine marinising, - converting from car to marine use

The gearbox also needs cooling and is done in a similar way using a keel tank. The engine transmits power via the flywheel through a drive plate into the gearbox and then its speed is reduced by a 2;1 ratio before it turns the prop at the stern. This also means I can keep the engine revs lower to make less noise, use less fuel whilst maintaining the same speed.
Almost all marine engines are puropse made for boats so in order to replace the car gearbox and mount the new drive plate, a bell housing has to be installed. I initially bought a bell housing from Lancing Marine, but after a lot of hassle, delayed delievery and then the wrong parts were delivered, I got rather cross and decided to make my own.
If Lancing had sent the right one, it would have been hard enough to copy theirs and replicate but as it was completely the wrong size and a different shape to my engine block, I had to start from scratch with some stiff paper, and acurately make a pattern to work from.

This type of problem solving is what I enjoy and do best. I love the challenge and the feeling that I won. Money cant buy that feeling.

The engine also has to produce electricity to keep the house battery bank topped up. This will be 12v and will be provided by a second alternator, the first one will also help out when its done its job of charging the engine starter battery.
The house battery voltage will be changed from 12volts to 240volts via an invertor, and then supplied via normal domestic sockets after passing through a fusebox.
12 volts will also be used for low power items like lighting because thats the most efficient way of doing it.

Inverting 12 to 240 volts is also ineficient. Losses of conversion waste energy and running a large 3kw inverter is also wasteful, so I shall split the load into two ring mains, one for smaller all day type loads and another for larger items like the washing machine and microwave which arnt used all of the time.