Re: buying a 1993 115 mercury what to look for???
i'm not sure what the compression should be on that motor, but the rule of thumb for any engine is 10%. meaning your lowest reading should be no more than 10% less than your highest reading. general appearance is a major factor in how well something has been cared for, check the skeg for chips, bends. with the motor off and in neutral, give the prop a couple of spins with your hand while watching the center of the prop shaft for any wobble from a bent shaft. this next one is very important!!! check the oil in the lower unit. you are looking for water in the oil. any sign of water here then "buyer beware". unless you are handy and have the special tools required to rebuild the lower unit, this will be expensive. carburetors are another neglected part of an outboard. carbs must be drained or the fuel line disconnected and the engine ran dry. the first choice is better. now just because this motor will start and run fine on a garden hose in the drive way may not mean it will perform on the water. take it to the lake before you buy it and run it. check your tattle tale. shift the gears and be sure everything seems good. make sure it starts easily once warmed up and as you throttle up it needs to be smooth. no stumbles, stalls or boggs. anything wrong here will more than likely be carb related and should not be driven any more since it will probably mean a lean condition which will cause expensive engine damage. check the charging system, put a volt meter on the battery with the engine off and check the reading. start the motor and idle it up a bit and make sure the voltage rises to say 13.5 to 14 volts. check the oil in the lower unit once again after you pull it out of the water. just a bit of water in the oil will turn it into a white foamy mess. if you decide to buy it, replace the impeller for piece of mind. hope this was helpful to you
