Re: Question on 18 HP cylinder heads

[johnyrude200]

Like others have said, 18/20’s are the same until the dreaded low tension magneto. Depending on the production run in ‘73, it could have either head and either the older or new style magneto coil placement.

You can put an old style head onto one of these powerheads right up to ‘76 if you switch back to the universal magneto which, IMHO, is better and easier to deal with anyway. May not throw as much voltage but SO much less hassle dealing with in terms of repairs.

Heck you can put a ‘76 head on a ‘59 just leave the coils off and go with the universal magneto so long as its a thermostat controlled model to begin with.

Check out these pics:

http://runneroutboards.com/motor101/powerhead/powerhead.html#18-20_Differences

You can see independant of the external mount coil bosses, these heads are the same other than the cupping for higher compression numbers used on the 25hp models. The late ‘73 production model 18/20’s with the bosses are the same as pre low tension magneto models in terms of cylinder cups.