Re: Old Johnson 125hp advice
Oh my goodness, don't do it. 1972 was the last year for Hydro-Electric Shift so we know it is at least that old. OK, in all fairness, that motor was state of the art in 1972. But in 1972 the world was much different than just a few years later. That motor was designed to run on Premium Leaded gasoline, before unleaded, before the Arab Oil Embargo. The motors had to be detuned to run on unleaded gas or they would blow pistons. And TCW oil, much different than today's TCW-3. We sold tons of that TCW, but looking back it wasn't nearly as good as today's product. Carbon buildup was a big problem. Part of that was due to the leaded gas, part due to the old oil. The shift was different as you know. There was nothing wrong with Hydro-Electric, but that was back then. A huge difference was the ignition system. It used the old battery CD system with a distributor cap under the flywheel. State of the art in 1972, but replaced with a vastly different system which was worlds better. We had a lot of trouble with water pump impellers. Seems like I was rebuilding a burned-up powerhead almost all the time due to instantaneous pump failure.
If your heart is set on more horsepower, get a newer motor, not an older one.
For your specific questions, no the controls and electrical systems won't work. The crossflow design was similar to the newer ones, but not identical.
