Mercury 2.5 C2 heads on a 225 promax with C3 heads.

Hello,
I'm finally building up my '97 225 promax with a brand shiny new block from Mother Mercury and a WSM piston kit after its been sitting and collecting dust for the past 2 years.
When it went down it mangled one of the heads. My brother has a mint 2.5 200 head for me (part # 18468-C2).

Question: If I get this head cut to the same 35cc as my cut promax head will it perform the same or do i need to source an identical C3 promax head?

Thank you in advance for the info.

I have a set of 2.5 200 heads that are cut to 34cc on one of my promax's seems identical to my other set of factory heads that are cut to 34cc other than one set is black and I had to drill and tap for a water temp fitting where in the other set a plug was in it there.

Other than that I can tell no difference.

NO!!! The squish band on the 18787 C3 heads are different than the 18468 C2. The 18787 C3 is the head you want to use or have matched with your existing C3 head..

Quote:

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Originally Posted by Fullthrottleguy

Hello,
I'm finally building up my '97 225 promax with a brand shiny new block from Mother Mercury and a WSM piston kit after its been sitting and collecting dust for the past 2 years.
When it went down it mangled one of the heads. My brother has a mint 2.5 200 head for me (part # 18468-C2).

Question: If I get this head cut to the same 35cc as my cut promax head will it perform the same or do i need to source an identical C3 promax head?

Thank you in advance for the info.

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What's the difference in the squish band? Are they a different angle or is it the size? I'm curious because I'm playing with squish band designs. Thanks for the info.

The width of the band is different and the bowl configuration.

Quote:

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Originally Posted by FORBESAUTO

What's the difference in the squish band? Are they a different angle or is it the size? I'm curious because I'm playing with squish band designs. Thanks for the info.

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Ok - thank you for the info.

Do you know if all else was the same (cc/cranking compression) would the different squish band effect engine performance on the promax if i put two 200hp heads on it?

Thanks!

cc's are cc's no matter the bowl configuration. But it does have a affect on the Burn from Squish band to squish band.

Quote:

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Originally Posted by Fullthrottleguy

Ok - thank you for the info.

Do you know if all else was the same (cc/cranking compression) would the different squish band effect engine performance on the promax if i put two 200hp heads on it?

Thanks!

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Quote:

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Originally Posted by Fullthrottleguy

Ok - thank you for the info.

Do you know if all else was the same (cc/cranking compression) would the different squish band effect engine performance on the promax if i put two 200hp heads on it?

Thanks!

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I have seen no measurable performance difference in the two on lightly modified promax's.

There might be some difference but its so slight unless you are data logging with high accuracy and repeatabliliy you won't notice it.

It does have me curious as to how much difference there is in chamber now. I haven't seen any but I've never broken the calipers out on them only a tape.

Maybe if i get really bored one day I'll make a dyno pull and swap heads and make another but I doubt it. Seeing as I've seen no measurable performance difference on my boat