Do not expect there to be a formal written 'service history' like you get with a car (often in a special booklet). Many boat owners are able to service engines themselves. In this case, at most there might be a handwritten note showing dates of service and perhaps receipts for filters, oil etc. If the servicing has been done by a third party there will hopefully be receipts or invoices available, but there might not. Have a good look in the engine bay - does it look clean and tidy? Does the engine itself look reasonably clean, as if it has been tended over the years? Also, it is not uncommon for the LED engine hour readouts to fail. Ours often only appeared after we had been running a while and the instrumentation had warmed up. The mechanical counter should still be working though and it isn't too tricky to replace the LED display (I understand). I think the state of the engine bay is a good reflection on the overall state of a boat. Very best of luck with your search and welcome to the forum. I well remember the nerves and excitement.