"Oil temp of 90 C is low, and
"Oil temp of 90 C is low, and not high. It should go to 110-130C.
What might be interesting is the indicated change of both pressure and temp.
Anyway if Your heat exchangers have never been cleaned and the boat has been used in salt water I would start by giving them an 'acid treatment'. There are two exchangers, the first one is for engine cooling water, the second is the oil cooler. Another problem might be the raw water supply and/or discharge. Worn impeller/pump or partly clogged exhaust riser. I do not know if You still have the original BMW exhaust riser, or the later VM cast iron riser."