Tracy D'arth

You will have your work cut out Frank there seems to be many problems that you are aware of to keep you busy. Welcome to the forum. The water ways should not be blocked unless it has been running in salt water. Expect corrosion though long term, the BMC engines being vehicle derived were never intended for fresh water cooling directly, they were OK with a heat exchanger.

Perhaps this uncontrolled trickle charging is what the battery makers are warning of. Does anyone have an uncontrolled charger these days apart from PV cells? I have just fitted a Durite 20A charger to an old bank of batteries, it seems to be restoring some life to them, switching from main charge to float at regular intervals with the cooling fan cycling too. Impressed for the price so far.

A small solar panel will top up batteries but they must be fully charged regularly. So if you have anything using the batteries whilst you are not on the boat eventually, quite quickly, they will sulphate and die. Many modern batteries come with a warning not to trickle charge them which is what a tiny PV panel will do.

How about some photos? Its difficult without?

Its very dark In January so you will get next to nothing on the solar most days. Your batteries are toast. Not on the way out but dead. Your charging regime is not sufficient to keep lead acid batteries in good order, you need to charge to an end current of a few amps, 20 to 30 minutes is simply not the way to do it. All the battery nerds will turn up soon.............................................

I was saving that bare wire for later, didn't want to frighten the OP off too soon.

The Middlewich branch is going down fast, there is no water going over the weirs.

Pull it out and see what bolt will screw in. Though most likely metric, Japan uses some odd pitches.

It does look like raw water cooling. I would agree that it is a home marinization as the spill rail is plastic pipe, did not comply with regs for inland waterways but things change,

Its an upright can though.

I see what you mean. Try this Vertical foam gun technique Amazon sell these https://www.amazon.co.uk/Foambeak-Vertical-Expanding-Insulation-Inches/dp/B01EAZJWG8/ref=asc_df_B01EAZJWG8/?tag=googshopuk-21&linkCode=df0&hvadid=427881625368&hvpos=&hvnetw=g&hvrand=2904057704448331712&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006912&hvtargid=pla-570711349423&psc=1&tag=&ref=&adgrpid=99265833763&hvpone=&hvptwo=&hvadid=427881625368&hvpos=&hvnetw=g&hvran

https://www.screwfix.com/p/no-nonsense-foam-applicator-gun/28483

Yep, BMC 1.5D. Made by BMC or later Leyland or even an Indian late production, marinized by Lancing Marine. A very common and popular boat engine.] The gearbox could be anything, need more photos to give you an answer.

Screwfix also extra stick grade. You need solvent too to clean the gun. https://www.screwfix.com/c/sealants-adhesives/expanding-foams/cat850108?brand=no_nonsense&foamtype=gun_grade&volume=750_ml&cm_sp=managedredirect-_-sealantsadhesives-_-nnfoamgungrade750ml