bought a 91 75HP Mercury that's been sitting. What should I do before I use it?

[udoittwo]

Hello again,
I have been trying to rebuild my 1986 75 HP and running out of time. Yesterday, I bought a 1991 75HP. It fired right up with the nasty smelling gas the seller used to show me. It came with a new or at least rarely used gas can, working titl/trim, complete trottle controls, nice stainless prop and nice original. The steering is frozen and he cut it off, but it looks the same as the one on my1986 75 and that is new so I hope I can switch it over. My guess is its been setting for several years. Compression is 107, 110, 109. I'm not sure what the compression should be and I don't know if it would improve with a warm motor or just using it a little but they are all similar, so I felt the motor is worth a try. I guess it was used in salt water as the powerhead mounting nuts are all rusty[don't they use stainless?], the anti-corrosion metal epices are in bad shape. It was not attached to a boat and could not be test driven. The guy was moving and he had 2 boats and lots of boating stuff to get rid of. Also bought a real nice plastic heavy live well with working pump for $50.
3 ?s.
1. I paid $750 for everything. I HOPE I made a decent deal but I have no real idea. Does that sound like a reasonable price?
2. It laid on its side for a while, is that bad for it and what should I change before I attempt to run it or prep it to fire after setting for a while? The oil injection take is full. Does oil hold up for a few years?
3. What can I do with that nasty old gas? I asked my neighbor the fire chief and he just told me to leave it evaporate. It would take years in that can and that can not be the correct way. We are no allow open fires in my township.
Thanks again for your help,
Karl.

 

[Texasmark]

Usually clean up/replace/kits anything that has touched fuel, replace the impeller in the water pump and drain and refill the lower unit hoping that the oil there is not yellowish or milky colored indicating a leak and potential problems due to corrosion there. I'd go a step farther and replace the thermostat and at least check the popoff valve.....both these are on the rear of the engine block, upper left side, under a cover with bulges on either end, held on with 2 screws.

Then fresh fuel in the tank and adding Sea Foam per instructions on the can can't hurt and I use always.

The compression is ok and the Sea Foam over time probably will make it improve by loosening any stuck ring problems you may have. With these loopers they use two wedge shaped rings, not 3 conventional shaped, and to work right the ring has to be able to move freely to seal up on the compression stroke.

Mark