User Tag List

Results 1 to 8 of 8
  1. #1
    Join Date
    Aug 2011
    Location
    Ontario
    Posts
    278
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    0
    Likes (Received)
    2
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    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.
    1986 Hydrostream Valero YT - Fully restored '12.
    1997 225 Promax.

  2. #2
    Join Date
    Mar 2010
    Location
    houston, tx
    Posts
    1,264
    Thanks (Given)
    31
    Thanks (Received)
    42
    Likes (Given)
    164
    Likes (Received)
    180
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    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.

  3. Likes FORBESAUTO liked this post
  4. #3
    Join Date
    Aug 2007
    Location
    North Eastern North Carolina
    Posts
    7,433
    Thanks (Given)
    62
    Thanks (Received)
    61
    Likes (Given)
    106
    Likes (Received)
    364
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    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 Originally Posted by Fullthrottleguy View Post
    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.
    Bud Conner "Heathen" "Defending Our Constitution"

    FOR ALL ENGINE APPLICATIONS
    DRY Film Lubricant for Piston Skirts & Cranks + Thermal Barrier Ceramic Coatings for Piston Tops, Combustion Chambers, Valves etc !!

  5. #4
    Join Date
    May 2014
    Location
    Livingston, Louisiana
    Posts
    1,166
    Thanks (Given)
    36
    Thanks (Received)
    77
    Likes (Given)
    162
    Likes (Received)
    208
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    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.

  6. #5
    Join Date
    Aug 2007
    Location
    North Eastern North Carolina
    Posts
    7,433
    Thanks (Given)
    62
    Thanks (Received)
    61
    Likes (Given)
    106
    Likes (Received)
    364
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The width of the band is different and the bowl configuration.


    Quote Originally Posted by FORBESAUTO View Post
    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.
    Bud Conner "Heathen" "Defending Our Constitution"

    FOR ALL ENGINE APPLICATIONS
    DRY Film Lubricant for Piston Skirts & Cranks + Thermal Barrier Ceramic Coatings for Piston Tops, Combustion Chambers, Valves etc !!

  7. Thanks FORBESAUTO thanked for this post
  8. #6
    Join Date
    Aug 2011
    Location
    Ontario
    Posts
    278
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    0
    Likes (Received)
    2
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    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!
    1986 Hydrostream Valero YT - Fully restored '12.
    1997 225 Promax.

  9. #7
    Join Date
    Aug 2007
    Location
    North Eastern North Carolina
    Posts
    7,433
    Thanks (Given)
    62
    Thanks (Received)
    61
    Likes (Given)
    106
    Likes (Received)
    364
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    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 Originally Posted by Fullthrottleguy View Post
    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!
    Bud Conner "Heathen" "Defending Our Constitution"

    FOR ALL ENGINE APPLICATIONS
    DRY Film Lubricant for Piston Skirts & Cranks + Thermal Barrier Ceramic Coatings for Piston Tops, Combustion Chambers, Valves etc !!

  10. #8
    Join Date
    Mar 2010
    Location
    houston, tx
    Posts
    1,264
    Thanks (Given)
    31
    Thanks (Received)
    42
    Likes (Given)
    164
    Likes (Received)
    180
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Fullthrottleguy View Post
    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!
    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

Similar Threads

  1. Mercury 300 PROMAX Heads
    By kylesbdsmerc in forum Misc. Parts and Accessories
    Replies: 4
    Last Post: 11-12-2016, 09:49 AM
  2. Mercury Promax 300 HP Heads
    By slow ride in forum Misc. Parts and Accessories
    Replies: 4
    Last Post: 07-21-2013, 09:30 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Frank Mole Transport