Well being that that's what I would call a well care for motor, you have two choices. Test the motor and possibly leave some major components alone or just replace everything maintenance wise so that you have a starting point for the rest of this boat's life.
So if we pretend like you have no records and have no idea if the former owner did anything at all this is what I do.
Starting from the bottom take off the prop, whenever I work on a boat I usually leave the prop off so I don't ding it. Inspect all the prop but mainly you want to grease the prop shaft so it comes out in the future. Then we move to the gear case, remove the two screws that hold the gear case oil carefully watching for any water that might come out. If there's any water at all need to find out the source of the leaks and fix them. That will save you a lot of dough.
I would go ahead and invest in the small cheap plastic pump that goes on the Marine gear case bottle so that it's easy to do. Lots online how to do this.
I would do that every year regardless. Knowing what's in there is more important than having new gear oil.
Water pump. Everyone on here says about 5 years on the water pump and I believe that's more of an average so I do it more as to whether I think it needs to be done. Pull off the gear case inspect the kit and see if you just need an impeller or a whole kit. Oftentimes I just change the impeller. By an IR gun and shoot the motor all over the place and make sure that it's not overheating. Just because the pump is pumping water does not mean that the rest of the engine is getting the cooling.
Learn how to grease the drive shaft properly before sticking the gear case back up into the rest of the motor.
Obviously grease all zerk fittings.
Check, clean or replace all spark plugs.
Each season test the overheat sending unit (simple switch) and the vro warning horn. Those motors all kind of vary from year to year but I believe you should have an intermittent beep for low or no oil and a solid tone for the overheat. Overheat is simple, find the tan wire on the back of the head and there should be a rubber cover over The wire. In that wire you can stick some type of metal poker and ground it to any bolt. All that sensor does is ground. Your key must be on an order for the horn to go off. If the horn doesn't go off you'll have to open up the box and test the horn and make sure it works. Replace what's ever broken. I'll let you go online to figure out the vro but I have a feeling you somewhat no motors and probably figured out yourself.
After that it's just about whether it's running correctly and I would need to know individual issues in order to offer suggestions. Always run with good fuel, always top off your tanks in the winter, and try not to ever buy ethanol diluted fuel. There's a website you can go to that shows you all the stations across America with ethanol free gas.
I do all my servicing before I put the boat away for the winter so that I know what shape it's in and so it's ready for the following year. After washing and scrubbing mine, I usually douse it in a half a can of WD-40.
After that, I tell her that she's been a good girl and I can't wait for spring!
Ps, did I talk about fuel filters?
