A brilliant motor, mine is a very late production one - 1986 - which at a guess has done over 10k hours.....The hourmeter stopped about 12 years ago at 5k...
It sounds as if you have a FW cooled one with the Volvo header tank at the back of the engine. Mine has a 3rd party one ( Bowman) on the bulkhead adjacent to the engine. This was fitted at birth so I don't know if there is shortcoming in the Volvo system or not but FW systems seem to have been an issue with a few Volvo designs over the years.
You probably have a Volvo FW circ pump on it ( see my photo
... the pump has a 'Yanmar Grey' pulley on it.)
They have a rubber/ceramic seal set up. Sooner or later the rubber seal will fail and that will lead to tears.
Let me tell you a little story... mine failed ( both seal and bearings) a long way from town when motoring in a glassy calm. New one aquired from the Volvo agent in Pto Montt... failed right out of the box.. replaced uner warranty.. next one gave a few hours and then failed... Volvo Chile
refused to replace as not fitted by their man.... taken by a friend to Finland
and changed under warranty... failed at under 50 hours.. new one posted from the UK... failed... 'nother one supplied by JJ Marinecraft in Melb ... failed within hours. My man at JJMarinecraft had the wit.. rather than sending it back to Brisbane
... to have it rebuilt by a local pump shop at no cost to me...
That was 8 years and many many hours ago...still OK but I do carry a spare one. I would suggest a bit of preventative maintenance
on your part.
Ditto the lift
pump... rubber diaphragm
failed on mine.
The starter motor? left handed... so not easy to find... buy a spare one...my spare one came off an MD17D that was being scrapped.
Depending on how long you are planning to keep the engine it may pay to buy a head gasket
kit and put it aside.
Thats about it really.... and if not done already I would suggest changing all the hoses... it was a hose failure issue ( hardening and leaking at a termination) on mine that lead to me needing the head gasket