Re: Starting a Mercury 115HP That Has Been Sitting
Don't use starter fluid, it has no lubrication in it and is bad for the motor's innards. You can pour some 50:1 pre-mix in a spray bottle, then carefully spray that in the carbs if it doesn't want to fire readily.
This motor does have an enrichening system, rather than choke shutters, so as long as you pump the primer bulb firmly, then crank over while pushing the key in (or pushing a choke button if you have that type of control box), it should spray fuel directly. Hopefully they drained the carbs when it was put away.
It certainly won't hurt to spray a bit of fuel in the carb throats to start out with.
Do you know if the impeller was replaced before the motor was layed-up? If so, the blades would be curled-up somewhat but there should be no fear of breakage.
Otherwise, and especially if you don't know the history of the pump, I'd go ahead and drop the lower unit and renew the impeller before you even try to start it for the first time. Definitely before you go out on the water.
Cheap insurance, and if an old impeller blade were to break and get pumped up into the system somewhere, you'll have a lot more work tearing things apart (including a possible powerhead & covers removal) to find the errant chunk o'rubber!
Unless the mechanic replaced the fuel pump diaphragm/gaskets when the carbs were rebuilt, there's a possibility they could be dried out and not function properly. You can give it a try for the initial startup, but I'd recommend installing a diaphragm kit before going out on the water. There are 2 different styles of pump, the older long-style with roundy-ends, and the newer square-style. Be sure of what style you have before ordering parts.
Also check fuel lines for deterioration, they're 26-years-old (doesn't time fly??)! They can look good on the outside and be bad on the inside, sending chunks of rubber to plug up the carbs.
Check all the large and small rubber lines, fuel or otherwise, for cracks, splits, etc. Many of the lines connect to the crankcase and if they leak, it'll suck air into the crankcase and lean out the mixture.
If the lines look like new and are nice and flexible, that's a good sign.
And yeah, if you can get non-ethanol fuel, by all means use it! Ethanol is Bad Stuff; it tears-up fuel system hoses & corrodes carbs. A real Boon for outboard mechanics but Bad News for the owners!
HTH & let us know how your Tower of Power runs.........ed