Most older F/W boats of that era came with OMC Cobra drives vs the Merc Alpha drives so double check that, they are similar in the fact that they use dog clutch shifting but everything else is different. The engines are basically the same except for the add ons. I would:
1) Change the motor oil and filter, unless you can tell it was just done
2) Change the water separating fuel filter dump the contents into a mason jar, let it sit, look for debris and water, you may need to clean out the gas tank esp if its the original tank. I have the same boat, have not had to do that to mine, yet.
3) R+R the outdrive, check the drive shaft bellows for water, make sure that the gimble bearing turns very smoothly, and the u-joints are not loose or tight, grease both. I do this at the end of each season, including a drive oil change, and look for water in the drive oil.
4) The other important maintenance item is the cooling system, this includes the raw water impeller (in the outdrive on both the Cobra drive and the Alpha drive, Cobra is much easier to replace), the thermostat, and the exhaust manifolds and exhaust elbows. The problems you can have is the rubber impellers wear, they should be replaced every 2-3 seasons, the thermostats can get corroded and stick and the cooling passages in the exhaust manifolds and elbows can get clogged from rust. In fresh water this issue is not nearly as significant as in salt water, here in salt water we usually replace the manifolds, elbows and thermostat housing every 5/7 years to avoid problems.
5) on a boat that old, make sure to carefully inspect all the fuel lines for cracks, and leaks. The F/W H-200 has a hatch over the fuel tank you can take up and inspect all the hoses and connections, also check the one at the fuel filter mount.
6) before launching run it on the water hose with a good set of ear muffs, check for:
proper running temp (160-175*F) oil pressure (cold idle about 40-50, hot slow idle approx. 20 psi) voltage (charging volts should be approx. 13.5-14.2, best if checked at the battery with a digital volt meter.
If it starts to overheat on the water muffs you got some work to do. Even if it does not, I'd put it in the water and before heading out, run it at the dock to make sure the engine doesn't overheat, on your first run, be aware of engine temp, oil pressure and voltage. Bring an IR Temp gun to check the temp of the exhaust system, at idle it should be between 80*--100* and after running on plane, about 125-135* or so, use the IR temp gun so you don't burn your hand if its hotter than it should be. Also check the bilge for water a few times on your first run. If there is no rain water you should NOT accumulate water in the bilge!
lastly safety, is paramount. You have an inboard gas engine, and you should be aware that fuel vapors can collect in the bilge and cause an explosion! So, every time you are going to start it:
Open engine hatch, sniff for vapors...if you smell gas DO NOT START IT! Find the source of the leak!
If you don't smell fumes, then run the blower for 4 min before starting with the hatch open.
When fueling at the gas dock, same thing. Turn all electrical off including the blower, on some boats it can pull in gas fumes from the dock. Close all hatches, then fuel the boat, make sure not to top off that can cause fuel to back out of the vent into the water. Next open the engine hatch and sniff, should NOT smell fuel. If ok, run blower for 4 min before starting. This is no joke, you MUST do this, I have seen ignorant people at the gas dock ignore this many times so far have not seen a boat blow up but it does happen.
Running a gas inboard....every year check all the fuel hoses....install a gas vapor detector...as a back up....but your nose...is actually more sensitive....
Hope I did not scare you off, but this is what I've learned over the years....
PS here's my '88 H-200...
