Tiny engines

Will you ever learn the difference between watts and watt-hours? Nope. Yet you're convinced you're qualified to give advice!

I haven't found anything less than a foot long. Perhaps you could belt a car alternator to something like these:
-jsw

Something like this, perhaps???

Absolutely.
Hardly. If we were underway, the iron genny would be charging both sets of batteries. But when you show up at the mooring and the bilge pump has run the house battery string down, and the Volvo would not crank fast enough to start..... then what?
And anything onboard not lashed down/stowed is soon in midair...
(It's a Alberg37, displacing 16,800+ lbs, with a 3 cyl. Volvo. And no oars included....)

I know a number of people, myself included, that kept a small gen set in a locker for just that sort of thing. In my case the stern locker was vented overboard so I kept the cooking gas and the gen set in the stern locker and just moved the gen set on the aft deck when I wanted to use it.
It was an AC generator which can be quite useful of you have any electrical tools or kitchen gadgets and a small battery charger served to keep the batteries up to snuff.

Yep, but we won't carry gasoline, which makes it harder.
Can I assume you're a sloop?

Yes 40 ft. actually registered LOD was 39-7/10 Ft. GW 16 tons We lived aboard for about 10 years and sailed mainly in S.E. Asia.
As for gasoline aboard, I carried about 5 gallons in a bright red jerry can on the side deck, forward. And was careful about filling outboards and gen sets :-)

Nice job! I have a slightly newer Briggs & Stratton model 6BS, on a Hahn Eclipse Rocket reel mower.
I try to suggest currently available products as old stuff like most of my machinery is hard to find and may have antique value:
Any similarity of this place to a museum.is purely coincidental. -jsw

Bring a freshly charged lightweight Lithium jump starter pack?
Lithiums are expensive for their Amp-hour capacity but they are small, light and well packaged to bounce around in a vehicle. The power terminals on my Whistler Mighty are recessed behind a snap-shut rubber flap. It comes with a rugged zippered nylon case to protect the battery, cables and chargers.
Better rated:
Perhaps you should look into why the solar panels didn't charge the starting battery.
Older batteries may require higher charging voltage. My testing indicates that they come back to normal if topped up periodically, like monthly, though some of mine have degraded in two weeks and needed 15V or more to restore them, which the usual charger won't provide. That's why I built my own metered adjustable grid / solar charging controllers and prefer batteries with caps to check and top up the electrolyte.
I don't (yet) have a good plan to obtain long life from unattended outdoor batteries. I have to set the charger voltage and current to match their condition. My industrial experience was all with systems the users maintain, like telephone exchanges, portable medical devices and the Segway.
Recently two of my 12V 7A-h AGMs failed with a bad cell. The only symptom while charging is the current doesn't decrease below 1% of the A-h capacity in a few hours, otherwise the charging voltage appears normal, but they drop below 11V when briefly loaded.
There are computerized chargers that test battery condition although I think I can do more with lab test equipment including a carbon pile load tester. An automatic charger that included one would be dangerous if it malfunctioned. -jsw

Put a "motor snorkel" conversion on and run Propane.

I never have that problem. I keep my daily driver on a trailer which is never more than extension cord length from my house. I leave out the drain plug in case it rains. Works for me so long as the old lady pays the Pacific Gas and Extorsion bill. VBG
Yeah, earthquakes, BTDT. Supplied food and power to my entire neighborhood several times.
I'd like to have that. I usually get my boats for free but Id be willing to pay a few bucks for yours. Cash is a little tight but I could make $10 a month payments now that the Trump economy is gaining traction! Six months OK? Let me know.

Why don't you fuck him up instead of writing impotent nonsense? What was the point of all the tough guy talk if all you're ever going to do is yap?
When will that generate enough cash to pay your current taxes,

Beautiful! At about four years old, I remember discussions about how to hook up an exhaust pipe to the one on my aunt's washing machine. The discussion degraded to how the exhaust system could be applied to my Grandmother. I wish I still had some of the motors I collected over the years then donated to numerous nephews as power sources for go-karts - small B&S with both vertical and horizontal spark plugs, Iron horse like yours, Muncey outboards, Evinrude four cylinder 5HP (cylinders fired in pair) outboard that I bought for five bucks in two cardboard boxes, a couple of English "Suffolk Supreme"engines from reel mowers. Ido have the 3HP Johnson that Dad and I bought new for $150.00 in 1954, must get it out of the shed and get it running, It only has around 200 hous on it and hasn't been run since 1981.

I guess I wooshed you on that reference....

Not sure what brand of trailer winches up an Alberg37; and mast clearance and power wires, overpasses etc. while towing it home just *might* be an issue...
As for free, I'm not the owner, just a deckhand. But he must have been wearing a mask, as he stole it at what he paid for it.

(smile ) But I came on the sloop "Kestel II".