Starting Mercury Outboard after 20+ years

[jam3s]

Hello

I have an old mercury 4hp 1977 GNAT outboard that has been sitting in our garage for 20+ years without any use. The outboard was drained of fuel when left and I have checked the plugs which appear to be in good condition.

I was planning to:
- add a couple of drops of TCW3 oil into each cylinder
- Change the gear oil
- replace the water impeller

Is there anything else I should do before starting the engine?

Also is all gear oil the same? (the manual quotes quicksilver 92-13783A24 which seems to be hard to find.)

Thanks for any help

[Locozodiac]

Is the carb immaculate clean inside ? let's hope you don't have a stuck piston already. If so will need to soak piston in W-40 or any other penetrating product for some time untill frees itself.

All gear oils are SAE multigrade 80/90 or 90 fixed grade ones. Can use any.

Happy Boating