Johnson 20 vs. 15

[thatone123]

I have run the OMC 15 for a long time and they are great. Been playing with the Johnson 22 cid circa 1967 lately. These are bulletproof but suck twice the gas of the 15. The 20 really has a lot of torque and it is quite a bit lower rpm than the 15 and sound completely different. The 15 screams with high rpm which I am used to. My question is how do they get the higher rpm with the 15. IS it mostly carb? or what else do they do? The 15 made its start in the market in 74 and is a more modern motor I believe.

 

[Chinewalker]

The 20 might be referred to as a long stroke, lower RPM motor. It gets its power via cubic inches. The 15 is a shorter stroke, higher revving motor, getting its power by way of RPM. The 15 also has an exhaust tuner in the leg which helps squeeze more revs out of it. As you noted, the 15's lineage dates back to 1974. The 20 dates back to 1953 as the first split crankcase Evinrude Fastwin. 20 years difference in the core design makes a difference.

 

[thatone123]

Ok, thanks. that makes sense just like the short stroke Chevy 350 that came out in the 50's . The 20 is a great reliable motor that starts first pull with the old magneto points and condensers, but just sucks too much gas. It can haul a much higher load than the 15 with a lot less stress on the motor, but with rising fuel prices the 15 wins out.