Mercury 125 missing part throttle

[StevesLX]

So we just test drove a 99 pontoon boat with a Mercury 125 2 stroke outboard. It took a minute or 2 and a lot of cranking to get started. The guy had to squeeze the bulb about 10 times or more on 2 different occasions and then it started. A lot of blue smoke for a little bit and then it went away. The boat seemed to idle fine. We idle out of the no wake zone and off we went. I noticed he would gradually bump the speed and hold it there for a few and then do it again and hold it there and do it again and so on. The motor sounded good and seemed to run fine. We went about a mile down the lake total and then we slowed down and turned around. The guy never did go back up through the throttle then. He kept it part way and the motor would throttle up and then come back down all by itself and it would do this back and forth until he would move the throttle lever forward more. Then it would start doing it again. He then tried to just go straight forward with the throttle to WOT and it wouldn't throttle up. It acted as if it was going to stall if he didn't pull back on it. A few times it would sputter also. So before I go and drop $5000.00 on this thing I would like to know if I should run or is this a simple fuel issue or spark issue or what? Any help would be appreciated.

 

[Texasmark]

If the toon has been sitting in the water, I'd suggest that you have bad fuel, possibly water accumulation, and the carbs and complete fuel system needs to be flushed out. Then run something like Sea Foam gas additive to clean up carbon and what's left of any water or contaminants in the fuel. Other thing would be to change the oil in the lower unit. Get a Merc manual and see how. If the oil in the LU has water in it, it could mean problems, especially if it has been in there for awhile and the boat got seldom usage. It would be a pain to check the LU oil with the engine on the toon but worth it. Get a large flat blade screwdriver and tilt the engine all the way up. On the bottom of the lower unit is the skeg and above that is the lower unit gearbox bulge. On the bottom of that bulge is a SSteel slotted screw about the size of a dime coin. Remove it and catch a little of the oil and look at it. If any color but blue/black to black, or you see water droplets in it, then you have water and need to know if you have any damage. LU problems could be upwards to several k$ if you have any major problems.

If you go for another test drive, get some fresh fuel, if you are serious you could just buy a tank, fill it and take it with you. Run the engine long enough to get the fresh fuel in the engine and then see what throttle it will take. If it acts like it wants to hesitate, squeeze the primer bulb on the fuel line near the engine several times and see if the engine recovers. If so, doing what I said earlier should solve that problem. Basically that's a fine engine; I just retired from boating and sold my 90 hp triple, it's little brother.....a running dude I assure you.

Unless it's a piece of crap, $5k for that engine and a toon to go with it isn't a bad deal. You could get that for the engine, depending on condition.