With the trend towards far greater fuel costs, I've become increasingly intrigued by the prospects of hybridity.
So I thought I'd attempt to open a debate to allow those with more engineering-based opinions to chip in.

I'm aware through other research, that a next generation 2 KW output electric engine is shortly to be available. It should cost about £1600, and may be fitted internally or externally. So potentially its a submersible. It should be about 30% more efficient than units presently on offer. Which means it should be able to emulate the thrust of a 15 hp outboard.
A likely battery bank would cost about the same again.

That in turn means that it should be able to drive a 30 foot displacement hull in smooth water conditions at 4-5 mph. Something like a Broom or Ocean 30 hull for example?

Most of us accept that diesel cruisers produce one thing in excess (apart from noise and fumes) and that's electricity; most of which goes to waste except on short trips.

But the rest of the problem of hybridity would lie in the configuration.

One obvious low-cost route might be to replace one engine in a twin configuration with an electric unit and battery bank. This would give diesel single engined running/charging, and the prospect of engaging the electric unit for better manouvering, or single engine electric running when charged.

A feathering prop would probably be needed on the diesel unit to reduce drag when running electric.

Another configuration would be to add a submersible electric unit as a 'bolt on', but again low drag (saildrive type) props would be needed on the diesel unit or units.

And, and of course, not finally, there is the more complex true hybrid, with diesel and electric engines sharing the same prop, and same shaft as each other; the electric unit doubling as an extra generator/charger, when being turned by the diesel; the diesel disengaging via clutch.

The latter could I suppose, also operate as a yacht auxiliary hybrid, although it would be costly in terms of engineering and fitting.

Thoughts, anyone?

Very quiet indeed.

TH, I think there is something wrong with your sums.

One horsepower is 746 watts, IIRC.

2KW is therefore a bit less than 3HP.

Leaves a bit to find from somewhere.

All electric o/b manufacturers say do not compare petrol/hp to electric/w. I've no idea why that is so but certainly Brian Ward told me that a comparison based on simple knowledge and arithmetic does not apply.

Sounds like you've proved it, TH!

The logic is with your argument, KH and I agree that it makes electrical & engineering sense but the proof of the pud is TH's experience: if he says it pulls like a 5hp how can we argue? The manufacturers say don't make comparisons. Perhaps it's all torque?

Here (hopefully) are images

The beauty of this installation (almost a non-installation actually), is that it can take place without cutting about and otherwise altering the original nature and structure of a historic yacht.
Everything (except the batteries) is external and no moving parts operate within the hull. The engine arrangement is pure bolt-on (4 screws), but it was necessary to drill a 35 mm hole through the hog to take the stainless steel tube which carries the HT cables and control wires. I suppose I could have done this myself, but I'm always nervous drilling into hogs, so got Steve E to do it.
The cast mast weight has been removed from the mast, and I shall follow Doctor Tom's example with Moonshadow, and have the batteries fitted in a cage as mast weights. There's a 24 volt charger mounted next to them in the forpeak.
The fixed prop as (shown) is shortly to be switched with a custom folding replacement.
The standard ones are all for diesels and don't have the correct size/pitch configuration. And as I'm learning - with electricity you never have power to spare, so efficiency must be a mantra.

This looks really great - nobody would ever know if you are sneaking up the bank or sneaking a little boost from your battery bank.

The electro-Privateer project crawls on, and not without pitfalls.
One of the main issues has been fabricating/adapting a suitable folding or feathering prop.

The problem is that there simply isn't a range of these designed to work with electric engines, which is why most electric engine units to date have had to suffer with fixed props.
In order to persuade my experts (Darglow Props in Dorset), to engineer me something that folds (for sailing) and grips properly for thrust, I've had to issue them a complete warranty disclaimer - both on the prop and on any adverse effects it may have on the engine.

So we're settling on an adapted 13 inch flexifold two blade, with (I think) 11 inch pitch. The result will be too heavy for my needs, because these props rely on weight and momentum/inertia to operate.

What's really needed is a superlightweight folder with an electromagnetic operated folding/unfolding mechanism. Any retired development engineers out there?
The Batteries (Lifeline AMG) have arrived from America. I can believe they were developed for tanks! Look awesome, and so they should for the cost (about a grand with the VAT).
Robin at Phoenix Fleet is readying the HT loom, and with all their experience in electric craft, at least he'll know what he's doing.
Nick (Starlight Lady) is fabricating the battery support load rack for attachment to the foot of the mast. The theopry is the AMG's will load in on their sides, one atop the other, and then cross connect for 24 volts. There's a spring-loaded HT cut-off in the forepeak, together with the 24 volt charger.