Thanks Myles and James.
James has actually given me all I need, at least for now. Most of what I write below is just for background thinking and musing, rather than for generating responses!
My thinking on electric is a little bit different than the main posts on the group, which seem to be from people who are doing it, rather than, like me, thinking of doing it, or just thinking!
I believe that electric will develop naturally once people are comfortable with it, and can get it as a used and therefore cheap item. As someone pointed out when I first joined this group, and I now agree, it is probably not for saving money, but for other reasons that most people go electric. I also have the opinion that there seems to be a tendency to arrange something that compares to ICE, but in reality, the average ICE is way overpowered for the boat size/hull speed, at least in sailboat applications.
I have the two automotive 'generators' (with brushes, not alternators) already, and all I am interested in doing right now is having a motor or two that is DC, can run (performance not important - that comes later!) on 12 volts, and will not end up overheating at a rate so fast that destruction occurs before I can unhook it.
There are some information sources online regarding the use of automotive (or marine!) starter motors, and I have asked about this also here, but the information I get is probably unknown, or rather not common knowledge, as if others have not done it, then obviously no-one will know it. There is some mention online regarding use in robotics, but no information on continuous duty. There are also drive train issues for starter motors. A simple pulley on a generator is a far better beginning point.
So, by using a generator, I can fiddle, and any work and money spent will have a possibility of getting used on the final setup.
For a marine environment I see the weak point as being the controller. I would like to experiment on ways around this, mainly for cost reasons also, but also I have a suspicion that the use of controllers is a result of basing boat systems upon vehicle systems, where there is no natural slippage. This would also be driven by the manufacturers and sales sources for the controllers.
I can remember years ago in a machine shop seeing an electric motor that required a lever to be slowly moved up a series of contacts, arranged in an arc, as the motor speed increased. Presumably each contact had a heavy-duty resistor in the circuit. Simple and safe, no electronics to burn out just when needed.
Another idea I wish to fiddle with/look into is electric clutches from automotive air-conditioning compressors, and/or chainsaw style centrifugal clutches. I have the idea that maybe if combined with a flywheel, or maybe not, this might be another way to get things turning with less shock loads than a simple blade switch gives. I know that there will be an increase in power loss that cannot really be afforded, but feel that this is an initial capital cost tradeoff.
Then there are batteries. I once visited a house that was off-grid, and the guy had made his own batteries, using old ceramic kitchen sinks as the cases. An advantage here is that each case (if made of some plastic material) could be shaped to fit the boat as a first requirement. There is lots of space on boats that might be unusable for other things, but could be used for batteries if the battery sizes and shapes were a variable.
Anyway, just a bit bit of different thinking, that's all.
John
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