Just got a used 1981 Johnson 140. It was sitting in a garage for many years, so I had the usual problems with fuel pump and carbs full of rust, then the thermostat full of sand etc....Now it's acting strong out of the water, but in the water I get only 33 mph @ 4200 RPM, The boat is a 17 Mako, which used to run 56mph with the 140 looper, and 38 mph with the 110 crossflow. Right now it's just running very smooth, but very weak. Takes forever to plane, I have to play with the trim tabs to get on plane. Compressions are all 110-125. I have all new coils, plugs and wires, and set the floats when I took the carbs apart. For some reason I noticed (while checking for a bad coil) that when I unhook either of the two right spark plugs the engine drops a MAJOR amount of RPM. But with the left two, there;s a drop, but nothing really special. So I'm kind of focusing a little more in that direction of two weaker cylinders on port side, what could cause that? The two right plugs came out looking like almost bare metal, the left two had normal soot, barely any but noticeable. I'm running a 13.25/17 prop. Also have a 13/19 prop to try. The wierd thing to me is that the lower unit looks identical to the looper one I had on the last engine. The crossflow 110 lower unit was completely different.
Before I go changing props again, I want to figure out the ratio of the lower unit and get the right prop. I may even have to swap in the looper lower, the 110 was turning 5300 rpm with a 14.5x17 prop. (I had taken the Looper lower unit and put on the crossflow, then used that prop, the 110 lower unit broke). I know it could turn into Frankenmotor, but it's all fun to me, just takes me to the sandbar and we provide the entertainment.
I'm kind of wondering if my prop is ok, but there's a power problem? The extra clean plugs could be telling me I have a fuel ratio issue. It never acted like it was about to lean out ( been there before, know that feeling of dying off). Tomorrow I was planning of going through the timing, since whoever had it before had cranked the idle timing control all the way to the end of the set screw, and I just set it to the old factory paint marks on the threads. Maybe they screwed up the full timing as well.
I also have a set of 1977 140 carbs with the chokes, thinking of trying them. Also have the 77 high compression heads on standby. BTW I only run Avgas, which I get through my job, it's 100 Octane, leaded. After 10 years of it, never had any issues with the lead, and the 100 means basically 100% safe from knocking (for the most part). Avgas does not go bad like regular gas if it sits for a long time. I've ran airplanes that sat for 15 years after their owner died, and they run perfect, made full power.
So any recommendations on a prop for a 1981 140 on a 1974 17 ft Mako? This is the cross-flow motor, no hot rod. Wife likes it because it's quiet and doesn't shake the boat like the looper. I just want it to plane off like normal and hit at least 40 mph.......
Before I go changing props again, I want to figure out the ratio of the lower unit and get the right prop. I may even have to swap in the looper lower, the 110 was turning 5300 rpm with a 14.5x17 prop. (I had taken the Looper lower unit and put on the crossflow, then used that prop, the 110 lower unit broke). I know it could turn into Frankenmotor, but it's all fun to me, just takes me to the sandbar and we provide the entertainment.
I'm kind of wondering if my prop is ok, but there's a power problem? The extra clean plugs could be telling me I have a fuel ratio issue. It never acted like it was about to lean out ( been there before, know that feeling of dying off). Tomorrow I was planning of going through the timing, since whoever had it before had cranked the idle timing control all the way to the end of the set screw, and I just set it to the old factory paint marks on the threads. Maybe they screwed up the full timing as well.
I also have a set of 1977 140 carbs with the chokes, thinking of trying them. Also have the 77 high compression heads on standby. BTW I only run Avgas, which I get through my job, it's 100 Octane, leaded. After 10 years of it, never had any issues with the lead, and the 100 means basically 100% safe from knocking (for the most part). Avgas does not go bad like regular gas if it sits for a long time. I've ran airplanes that sat for 15 years after their owner died, and they run perfect, made full power.
So any recommendations on a prop for a 1981 140 on a 1974 17 ft Mako? This is the cross-flow motor, no hot rod. Wife likes it because it's quiet and doesn't shake the boat like the looper. I just want it to plane off like normal and hit at least 40 mph.......
