Hi, Jeniffer,
I am new to this group, and am in similar position.
Sorry if this all rambles on a bit, but that's my style.
I believe that the best setup might be to have both internal combustion, and electric, as a complete package. My thinking appears to be the same as yours, thinking as an overall thing, propulsion, heating, electricity, rather than just propulsion.
I was thinking maybe have a small IC engine, then a clutch, then an electric motor, then another clutch, then the prop shaft.
This would allow the motor to rotate when the IC engine was running, and it could be either charging the batteries, or have power supplied to it for extra power to the prop. And the IC engine could be declutched from the electric for when it is used for heating, or maybe charging using IC engine alternator(s).
As a guide for heating, I had a car that was about 3 litres, and when the radiator broke, I ran it for 2 weeks without one, just with the heater full on, this was in -30 Celcius weather, and running on a highway at maybe 55 to 60mph max. Any faster, it overheated. And it was like an oven inside the car.
The prob might be finding a liquid cooled IC engine that is small enough. But you can always run a bigger one with less throttle. My own 26 foot US built boat has an old sidevalve (flathead) 'Atomic 4' engine, which is basically a farm tractor engine, and is rated around 30 HP.
I am going to look into using automotive air conditioning clutches.
Looking at generators, most are air cooled, and could not be boxed-in unless you have large airflow past the engine. This would prevent use of such an engine for cabin heat, I think. But you might be able to put a heat exchanger on the exhaust pipe to heat water. Or coil the exhaust up, and have a fan behind it for cabin heat.
I would stay well clear of any fuel gases that are heavier than air. The petrol/gasoline engine is bad enough, and will need a fan system to purge the bilges of heavy vapours for about 5 minutes each time before starting the engine. If the fan is set up to suck from the bilges, it should be a marine grade sealed unit so no electric sparks ignite the inflammable gases. The other way is for a fan to blow in, and have the engine boxed in so that a pipe can be led from low down, and the vapours will get out that way as the box gets positive pressure.
Another consideration is the 240v mains appliances that you intend to use. If they are just small, then you might want to look at inverters, they are getting cheaper and cheaper, but I am in Canada, where the mains is 110v., so 240v ones might be more expensive.
If like me, setup cost is a big factor, you might look at a setup where used car alternators are driven by a lawnmower engine, aircooled, that you can mount outside the cabin, maybe. Then if you have an electric drive, with big batteries, you only run the engine when longer range is required, or for recharging.
The fact remains, I think, that the way to get relatively cheap power in amounts that give good safety margins, is to have a petrol or diesel engine somewhere in the mix.
A further option would be backup units. One suggestion I had given to me was a petrol powered 20 or 30cc 'weedwhacker' unit with a 'Minnkota' electric trolling motor prop fitted to it. This has been proven, apparently.
Speaking of which, I hope to soon be testing the capability of a Minnkota type trolling outboard - they are rated in pounds of thrust, the smallest giving I think about 30 lb.
The answer for me will be a mixture of methods.
I will be interested to see any other responses to your thread, I need similar help too, but not urgently, that's for sure.
One big question that no-one seems to ever answer is, can I just slap the power to a DC motor, without using a 'controller' (my understanding is that they are there to allow slow running) but just some form of heavy duty switch, such as a car starter solenoid?
I hope that this all adds info, rather than confusing things.
John
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