New to me boat

I would verify it has oil first. Install a new Raw Water Pump Impeller, Charge the battery or you might just put in a new one, 3 years is a long time, for$100 you will know you are good for the next 3 years.   Maybe pull all 8 spark plugs then with them out spin the engine over till it has oil pressure showing on your gauge. If your plugs look good reinstall them and get ready to fire it up.
If you have never pulled all 8 plugs at once you should mark all 8 wires so you can put them back in the right spot our your boat will not start.
Install a Timmy T ( see advice on this forum ) for $10 more dollars hook up a garden hose and start it up. Watch oil pressure, Temp and your Voltage meter. The temp should not exceed 160.
Maybe everything is perfect. Welcome aboard!
Note: a very few of these boats use a closed cooling system, more like an automotive system. If yours does have a closed system with a radiator you will need more advice and can ignore replacing the raw water pump impeller.
If you have one of these boats it is a reasonable duty to install a new raw water pump impeller every 2 years and ALWAYS have a spare on your boat. When they go out you are stranded.