Evinrude Compression

" What sould good compression

" What sould good compression on a 1974, ER,3cyl, 70hp
be ? "

They should be even( most

They should be even( most important ) those 3 cylinder motors were high on compression (160 psi observed on a 68 triple ) If you get numbers around 140 you will be OK. Keep in mind that engines with " pressure back " rings with high hours are subject to ring failure. The reason is that a standard ring when it wears does not increase side clearance.The pressure back ring (top only) has a high taper and therefor when it wears the side clearance increases to the point that the ring is "lOOSE " in the groove and at high rpm gets knocked around (rattles in the groove) and eventually fails.

" Sparky, It is better to chec

" Sparky, It is better to check the compression hot or cold ??? "

" Makes no difference,throttle

" Makes no difference,throttle setting makes no difference.You are looking to compare cylinders, after all you have 3 seperate engines with a common block and crankshaft. "

I totally agree with sparky.

I totally agree with sparky. as long as you are in the 135-160 range you should be okay. all three cyl. should be relatively close