Can any one tell me if a 1990 50hp lower unit will fit on a 1984 70hp? Also I checked the compression and the they read 125 122 105. What do you guys think of those numbers? The 105 has me concerned.
What is the type of your 50 hp. Is it the "normal" 50 (698 cm¤)or is it the 50 (849 cm¤)?? If it's the bigger one, then the lower unit will fit the 70hp engine.There is a smaller prop axle in the 50 (849 cm¤) than on the 70hp. The type is G-axle on the normal 50 and the "Big 50", and the 70's axle is K-type. The "Big 50" is called Pro50 or 50G here in Finland.
Yamaha 70 lower unit and compression
There is a smaller prop axle in the 50 (849 cm¤) than on the 70hp. The type is G-axle on the normal 50 and the "Big 50", and the 70's axle is K-type. 
Linear Mode
