Power Head Gaskets

[labrador-guy]

I noticed that the OMC 5 1/2 and the 7 1/2hp power head gaskets are slightly different. Anybody know why? Can they be used on either motor?

thanks dale

[frankr]

Should be the same, according to same year.

[fleetwin]

What powerhead gaskets are you referring to?

[1946zephyr]

Yes, the lower units and exhaust housings are the same, year for year. Everything above the powerhead base gasket will differ though.
The 7.5 was actually designed by Evinrude and the 5.5 was designed by Johnson. The two were not fully incorporated until 1956, when both nameplates went on ALL motors. Up untill 1956 the 3 and the big twin class were the only two motors shared through and through

[chris-p]

Here is the run down on Base Gaskets for the ’55 to ’58 5.5hp and 7.5hp OMCs. As you found, they can differ slightly. BE CAREFUL not to mix them up! Been there, done that.

EVINRUDE

MODEL YEAR HP PART #
5512/5513/ ’56/ 5.5/ 304314
5514/5515/ ’57/ 5.5/ 306205
5516/5517/ ’58/ 5.5/ 306205
5518/5519/ ’59/ 5.5/ 306205

7518/7519/ ’55/ 7.5/ 303467
7520/7521/ ’56/ 7.5/ 304314
7522/7523/ ’57/ 7.5/ 304314
7524/7525/ ’58/ 7.5/ 304314

[chris-p]

JOHNSON

MODEL YEAR HP PART #
CD12/ ’55/ 5.5/ 303467
CD13/ ’56/ 5.5/ 304314
CD14/ ’57/ 5.5/ 304314
CD15/ ’58/ 5.5/ 304314
CD16/ ’59/ 5.5/ 306205

AD10/ ’56/ 7.5/ 304314
AD11/ ’57/ 7.5/ 304314
AD12/ ’58/ 7.5/ 304314

[twostroke]

Thanks, Chris….I gotta’ CD-15 scattered and a buddy’s ’57 Evinrude 7.5 (that someone helpfully knocked the tag off…) and was wondering if I could mix/match some stuff outta’ my stash so he can go waterfowl hunting next weekend. This answers it…

Jim

I say "pardon me" a lot. I had a 20H, then raced open mod sleds.

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