"Can you elaborate more on what happens with the oil pressure senders?
Are these just alarms or to oil pressure gauge?"
These are just senders: I think, just a baffled set of contacts that open as the oil pressure increases. Sadly, I changed two things at once: I cleaned the engine
with the solvent (50/50 in the oil), AND purchased the new sender directly from Yanmar
, rather than off a shelf in a chandlery
. I have had no more sender problems. I replaced the sender for a few hours with a contraption with a proper pressure guage, and the oil pressure, at all engine speeds and loadings, remained within reasonable parameters, albeit at a slightly high end of the range.