Why not take your piston to a motor-cycle shop and/or an engineering shop that does rebores and ask them if they can source a piston-ring (or two) which would fit? Even one that is a bit too large diameter-wise, but ok for fitting in the groove could be ground down to fit.
You are right. With the bottom end of the mast weighted with whatever kind of ballast is convenient, the lifting point can be just a little above the ballast. It could be sandbags, chain, or whatever.
It's probably not relevant to your problem, but I've had two TP 10's. Both died of getting a little wet. I mean exposed to a bit of rain. What possible use are they on a boat?
Surely it is impossible for the oil pressure to remain high after the engine has stopped? The oil pump will not be running, and oil within the engine will be leaking out of the bearings quickly.
This points to a faulty gauge.
"If this lot would confine themselves to biting the insulation off live 240V cables we might let evolution take its course... "
Ha Ha. Darwin awards for rodents.
I recently bought one of these from ebay for approx £15 inc. postage for diesel transfer. Self-priming. 12v DC. Only used it a couple of times, but works a treat.
12V Car Transfer Self-priming Pump Extractor Engine Oil Tank Hose Remove Siphon 738603084140 | eBay
Admittedly a few years ago, but I used to get my boat craned out annually at Emsworth Marina for a week or so while I antifouled and did other jobs. I often stayed overnight as I live about 50 miles away, and had no problems.
I'm guessing from the spelling that "ferreteria" literally means "ironmongers". But the first thing that jumped into my mind was a shop full of ferrets :ROFLMAO:
I have an exhaust temperature alarm I installed over 10 years ago. Trouble is it simply sets off an alarm. There is no visual display, so it's impossible to know if it is working. I have just ordered one of the siliconmarine ones.