Big twin engine swap

[denislajoie]

ok sorry for the long post in advance but i ll try to explain the best i can. I have a older johnson 40 hp, older than 1967, its white, has a glass bulb on the fuel pump, and has 2 copper tubes for the water (apparently this help indetify it) its a manual shift it has no number plate or any munbers on the head or block, i also have a 1967 40 hp RK 29E i believe, electric shift, the first engine runs badly, only on one cylinder (top plug is cold after an hour on the lake) the 1967 runs excellent but the lower unit is screwed as all electric shifts are, can i swap the engine from the 67 onto the older body direct bolt on or will it not work cause of the shift linkage differences, or can i quickly or cheaply repair my older one, remember my time is worth nothing dollar wise and i have everything i need if they can bolt on so the cheapest solution possible, i dont mind spending money but only if i have to. thanks

 

[AlanR]

Re: Big twin engine swap

i cant really think of reason why not? See if the bolt holes line up on the lower unit

 

[itstippy]

Re: Big twin engine swap

I would first spend a couple hours troubleshooting the older powerhead. They're tough hombres and it's probably something simple gone bad due to age, like a bad coil or spark plug wire. Those Big Twins share a common carburater; since the bottom cylinder's running fine you can rule out fuel & carb issues. Do a compression test and a spark test on both cylinders. See what you've got. If the top cylinder's just lost spark and the bottom cylinder's been dragging it along "for the ride", you haven't hurt the top cylinder any. It's been merrily sucking in the fuel mix with the vital lubricating oil and spitting it out unburnt. Lazy thing, but no harm done. Do the comp & spark test. The powerheads will probably swap easily enough if necessary, but keep that ace up your sleeve until you need it.

 

[Paul Moir]

Re: Big twin engine swap

Glass bulb indicates '60-'63. Otherwise I'm in total and complete agreement with itstippy.

For swapping powerheads on BTs, the most important thing is the tubes. 2 tube powerheads swap, and 1 tube powerheads swap, but 2 tube powerheads do not swap with 1 tube powerheads. The base of the engines are shaped differently.

 

[denislajoie]

Re: Big twin engine swap

ok, the next time im down there i ll try to give it a good look over, i already changed the spark plug caps cause i thought that was the problem, it ran when i touched the bare wire to the top of the plug but itys hard to trouble shoot one cylinder not firing properly in a barrel of water cause you get all wet and the engine rattles so its hard to hoild the wire