Will a 66 20hp Evinrude powerhead work on a 70 18hp Evinrude?

[ggrace boater]

I have a 70 18hp Evinrude and I'm wanting to know if a 66 Evinrude 20hp Powerhead will fit on it. Does anybody know if it will work? Thanks

 

[emckelvy]

Re: Will a 66 20hp Evinrude powerhead work on a 70 18hp Evinrude?

The same # base gasket (314421) is used on both the '70 18HP and the '66 20HP. Here's the parts diagrams so you can verify it yourself:

Evinrude Lower Unit Group Parts for 1970 18hp 18002C Outboard Motor

Johnson Lower Unit Group Parts for 1966 20hp FD-20 Outboard Motor

So, they should interchange.

Note that the newer 18hp has a recoil starter interlock assy that you can't transfer over to the 20hp block since the older block doesn't have the casting for the interlock fastening bolt. But you can probably do without that feature, up to you.

The only other issue I could think of would be a difference in crankshaft/driveshaft splines (i.e. fine vs. coarse splines), but the part #'s for both years' crankshafts are the same.

HTH...........ed

 

[Chinewalker]

Re: Will a 66 20hp Evinrude powerhead work on a 70 18hp Evinrude?

Splines are same. Might be some small variation in carb knob locations as 66 had small carb, 70 had large body carb. Should be able to swap carbs by swapping intake manifolds, if it's an issue.

 

[ggrace boater]

Re: Will a 66 20hp Evinrude powerhead work on a 70 18hp Evinrude?

Thanks, I am going to have the 18hp carb and intake on it. I wonder if it will be a 20 or an 18. I'm going to leave the 20hp reed plates if I can. The 20hp powerhead I bought is bare so I am planning to put everything from the 18hp on it.

 

[kfa4303]

Re: Will a 66 20hp Evinrude powerhead work on a 70 18hp Evinrude?

Here's a handy link.

Maintaining Johnson E & FD Serie