johnson/evinrude V4 60HP CYL HEAD DIFFERENCES

[turtledoctor]

Maybe someone knows why mother OMC changed head part numbers on their V4 60/65 HP motors.
Cyl head part numbers 313756 and 313757 for the 65HP OMC look ABSOLUTELY IDENTICAL to heads 553758 and 553759 used one year earlier

both sets take the same head gasket and same cover gasket.

In checking the p/ns OMC does NOT list one set as superceeding the other.

Does any one know,,,,,seems strange that the later motor uses LOWER part numbers than the earlier motor

thanks to all
ED

[frankr]

Betcha the 60hp is lower compression motor than the 65hp. Betcha if you check real closely you will find the combustion chamber is deeper in the 553xxx than the other. The 60hp motor was a resurrection of the 60hp Gale motor. They just modified it a bit to make an extra 5 ponies. 553xxx are typical Gale numbers.

[fleetwin]

I’m thinking Frank is correct. The pistons are the same part numbers, as are the head gaskets. The hp went up to 65 in 1968 when the part numbers changed. It appears as though the carbs are the same, even though I could not find part numbers for the complete assemblies. High speed jets, carb body, and nozzles are the same part numbers. So, I’m thinking that using the 65hp heads on the 60hp engines would be OK, provided you replaced both heads so the compression is even on both banks….
Let’s see what Frank thinks about it….

[frankr]

Sure, as long as everything fits.

[turtledoctor]

FYI-I did check the head volume on both heads–the 1968 65HP one and the 1964-1967 60HP ones

NO DOUBT ABOUT IT–The 65HP head (pn 313756 and 57) have a much more SHALLOW combustion chamber,,,by about .125

It is NOT a milled version of the 553758 head as both heads have the same overall height

It is a different casting for sure,,,,all other dimensions appear the same

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