Okay so I went and spent a good 2hrs going over this old 100HP Merc. motor on the Carlson boat I want to buy. The motor is about a 1965. I pulled the cowling off and everything looked pretty clean (for 35+ years old). The owner takes really good care of the motor and has several receipts - one even totals $675 (from 1996) for replacing lower unit seals, impeller, propeller, etc... THE ONLY WEIRD THING I FOUND OUT HE DIDN'T DO, WAS NOT CHANGE THE GAS... He says he leaves the old gas in there all winter and it still fires right up? Okay so aside from having gummy gas in the fuel system (which may or may not get burned out over a tank or two) here is how the motor performed. <br /><br />I pulled all the spark plugs and checked the compression and it was as follows:<br /><br />CYL 1: 100 psi<br />CYL 2: 110 psi<br />CYL 3: 105 psi<br />CYL 4: 80 psi<br />CYL 5: 90 psi<br />CYL 6: 95 psi<br /><br /><br />I thought it was weird that the top 3 pistons had about 105 psi average and the bottom 3 pistons had about 90 psi average? <br /><br />I then proceeded to hook everything back up and check spark. IT HAS GOOD SPARK. <br /><br />Then I hooked up the gas and gave it about 4 or 5 pumps. I looked at the carbs and they were dripping fuel - I thought that was weird but the owner said it is just because I "over pumped" the primer (the pump). It made sense because everytime after that I pumped it - gas dripped out. <br /><br />Okay so after I cleaned up the loose gas, I fired up the key and the motor fired right up after about 15-20secs of turning over. Mind you this was the first time it had been started in 7 months! <br /><br />It was a little crackly and spurratic at first but after about 1 min, the "tell tale" was trickling, but not a steady stream, and the motor seemed to have warmed up a bit and was idling smooth. <br /><br />After about 3-5mins of idle, I suggest we turn the hose up a little bit. After we turned up the hose, the "tell tale" was trickling a solid stream, still wasn't streaming - but the motor wasn't the slightest bit hot. The owner said it never really squirts at idle, only squirts a solid steady stream at a little higher RPM. After about <br /><br />After a good 5 mins of idling the motor sounded fine - an occasional stutter or increase in RPM, but NO LOPY IDLE AT ALL. <br /><br />I asked if we could rev it up and he said okay but only let me push the "fast idle" lever fully forward, we didn't put it in gear because we were running it off the hose. At fast idle it sounded good. The "tell tale" pissed a little more water confirming the owners claim. I put a motor stethescope on each cylinder 1 at the time and they all sounded even. <br /><br />We turned the motor off, waited 30 secs and then turned the ignition and it fired RIGHT UP.<br /><br />I have a "in the water test ride" scheduled for this Sunday. Does this sound like something I should pursue? The boat hull is in REALLY GOOD SHAPE.
