Difference in OMC 70hp and 75hp heads

[BKS72]

I found a used head for my rebuild project, but it's from a 1983 70 horse. Part number for my 75 horse head is 0323682 and the part number for the 70 horse head is 0323681. Does anyone know the difference between the two and/or if I can use the 70 head on my 75 with no ill effects? Thanks!

Branden

 

[kynolan2183]

Re: Difference in OMC 70hp and 75hp heads

I would think you could use it. Study carfull for clearances and make sure thickness is the same or the head bolts might not have enough thread at the bottom (to thick) or the bolts may bottom out (to thin).
If the internal deisgn is different you mat lose 5 hp. That won't affect much.

Others may has a different opinion and more experience on the swap.

Make sure they look the same and have the same thickness and clearances.

Check careful before starting
Kyle

 

[BKS72]

Re: Difference in OMC 70hp and 75hp heads

Thanks man! That's kind of what I was thinking - the combustion chamber might be a bit smaller, but I don't know. The blocks are a different p/n as well, so it could be a different hole pattern or something. It's on Ebay and I spoke with the guy this morning, but it's kind of tough without being able to see them side by side. Almost everything else is exactly the same on the two motors. I've looked everywhere trying to find out the difference and I can't find anything.

 

[BKS72]

Re: Difference in OMC 70hp and 75hp heads

Bump.

 

[Dhadley]

Re: Difference in OMC 70hp and 75hp heads

As long as the replacement head is off of a 49 cid motor, it'll work fine. If it looks like yours (water jacket & t-stat covers with way too many bolts) it'll work.