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Here’s some notes I had on file from members………
Re: Johnson a-45
Postby Tom Manley » Fri Aug 26, 2016 10:30 am
I don’t have a manual or diagram, but I do have plenty of opinions…
With the exception of the compression release system, these are identical to the A-35 motors. And the powerhead is pretty close to the earlier Johnson twins. There is no water pump, as typically seen. This motor uses propeller thrust to force water up to the powerhead, and vacuum at the water exit in front of the propeller to draw water down from the powerhead. Here my considerations regarding restoring and running an A-45.
There may be backfire prevention deflectors, or whatever they are called, in the intake ports of the cylinders. You should consider removing these unless they are in excellent shape. When worn, they can migrate into the cylinders with very nasty results.
When reassembling the crankcase, crank, and rods, be sure the keyway is pointing to the arrow on top of the crankcase with the pistons extended to top dead center. It’s possible to assemble this powerhead backwards, and the spark will occur 180 degrees off.
The water passages and lines need to be air tight, or nearly so. This means that the compression fittings and supply / return lines need to be in good shape. Once the powerhead and leg are reassembled, and with the foot removed, blow low pressure air into the supply hole at the bottom of the leg, and plug up the return hole. Check for leaks. If you need to replace the water lines, aluminum tubing can be obtained from McMaster-Carr. It’s a lot easier to bend than copper tubing, and it’s the right tubing to use. Buy the roll, and swap pieces to people that need it, or ask to see if someone in the Club has some leftover from a project of their own.
Be sure the compression release is working properly. With the lever in the start position, the decompression valve should be open and the rotating valve should close off the intake port between the cylinder and the crankcase. In the run position, the decomp valve is closed and the rotating valve provides a smooth passage from the crankcase to the combustion chamber.
Likely you’ll need to adjust the gear lash in the foot, since experience has shown most of these to be out of adjustment. Disassemble the lower unit, taking care not to drag any burrs on the shafts through the bearings. Clean out the lower unit of all old hardened grease, and put a film of oil on the shafts. Reassemble the lower unit using the gaskets that will be in place when restoration is complete. Loosen the locking nut at the front of the foot, and back off the adjusting screw until there is some backlash between the pinion gear and the drive gear. Then slowly screw in the adjusting screw at the front of the foot. Stop when there is no backlash, then back the screw off a bit. Make sure the propeller shaft is pushed forward during this adjustment. Tighten the lock nut. Fill with the appropriate grease, not hypoid oil. Lots of people use Lubriplate 105, others use something a bit thicker.
When you run the motor, it may not pump water if run in a barrel. You need the forward motion of the motor on a boat, and likely you will need to get the boat moving a bit to get water circulating properly. The problem with these motors is that they run so well, and idle so well, that they can be started and idled right away, and the water may not get moving. Check cylinders often when running, to make sure they are not overheating. Don’t run the motor through weeds.
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Re: Johnson a-45
Postby George Emmanuel » Sun Aug 28, 2016 2:53 pm
Tom gave some really good comments about the A-45. One thing I was going to toss into the discussion is there were 2 variations on that motor and there was an article in the Outboarder some time ago about it. There were 2 different flywheels used for some reason. One is like the one on the A-35, the other, and this is what I have on my motor, is a much taller flywheel. Why the difference//I don’t know except the bigger flywheel obviously idles slower.
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Re: Johnson a-45
Postby Tom Manley » Mon Aug 29, 2016 6:09 am
Plug wires are 9 mm cloth covered copper core. Check Brillman on line. There are several suppliers, Brillman has been good for me. I can’t remember whether the A-45 has the bakelite retaining nuts on the plug wires. If so, they are pretty fragile. Use care when removing them. Get back to us if you need to remove them for replacement, or if the coil tests bad. (They simply jam the wire in place up against the coil contacts.) Do not assume the coil is bad if there is no continuity across the secondary leads. These coils are usually good. If you are roping the motor over to check for spark, be sure to ground one wire, or make sure both are connected to grounded spark plugs.Prepare to be boarded!
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