for the first few seconds is usual as it takes a moment to get the oil pressure up. If the engine heats up at higher RPM's running in neutral, ask for a look at the maintenance log to see when the impellor was last changed. That's frequently a source of problems and a thrown vane can get itself into the water-lines and restrict the flow to the heat exchanger
. (A pain in the neck but not a difficult fix.)
If the engine heats up in gear, find out if the running gear is clean. If not, that's commonly a source of overheating
as the engine is straining to maintain it's RPM's.
leak can be more of a problem. Firstly, check the point at which the line from the expansion tank connects to the throat of the coolant filler, under the cap. If the paint
on the top of the heat exchanger
in the vacinity of the cap is missing, either the cap or the hose connection are suspect. (I had that problem on our engine and learned that because the former owner had used a replacement filler cap from an auto-parts store, rather than a proper Perkins cap, the top of the filler throat was bent enough to allow seepage.) If that's not the source, next check the area around the temperature sensor, next to the thermostat housing--where leakage can occur around threads, the base of the thermostat housing itself for leakage around the gasket
; and, the fresh-water coolant pump and hoses, especially if the hoses run to a hot water
heater that uses engine coolant to heat a domestic hot water
supply. A leak in any of those or their connections could be the source of the coolant under the engine.
In conclusion, if the engine starts easily and runs smoothly, at $1,200 is probably a deal. A rebuild--i.e. rings, bearings, valve-job et al once it's out of the boat--would not be very costly, nor would cleaning
out the heat exchanger and replacing all of the gaskets, hoses and seals
. With that you'd have a very good deal--probably under $4,000 for a really good engine that--properly cared for, could easily last another 10,000 hours.