Results 1 to 6 of 6

Thread: Aftermarket Cylinder Heads 2.5 Merc.

  1. #1
    Anyone have aftermarket cylinder heads on 2.5 merc. 260 H.P.?Have you seen any performance gains?I do not want to raise compression ratio to the point of requiring race fuel.

  2. #2
    Unloaded Racing
    Do you have any idea what cc heads you want? I have a set of 28cc done by Jay Smith if you are interested.

  3. #3
    Hey' Thanks' Unloaded Racing for your reply.I need to find out what cc heads I have on a stock engine first.I realize that compression is h.p..I still want to use 93 octane fuel.I use the boat for pleasure but looking for more speed.Runs 90 mph on a 21 Liberator with 26 Masco RE4 at @ 7100 rpm.

  4. #4
    Unloaded Racing
    If your motor has the Factory stock heads they should be 37/38cc. Some of the Factory Mercury Heads are stamped on the side of the top corner. The cc of the heads can also be checked after removal with a syringe and water. Most Lakers run 28cc up. I ran the 28's on Mirage River Racer with a STOCK 2.5 carb motor and the boat ran 83-85 mph in the Quarter Mile. Let me know if I can help.

  5. #5
    28CC is way too tight for 93 octane though. To be safe you should be in the 32 CC range at a minimum. I have had a set of Wizard aftermarket heads. They're about 5 hp stronger than the standard merc heads at identical CC. I'm not sure they're being made anymore though.
    Milling them will give you a little more punch, but won't make a drastic improvement in top end speed.
    Sam Baker
    Baker Marine Support

  6. #6
    Thank you Scary fast. I just don't know very much about out board power plants and your information helps a great deal. Most folks in are area run I/O or Jets drive stuff.I also have talked to Chuck Goodman at Nitrox Injection Systems about Nitrous Oxide.His system sounds good in theory and design but not sure if the motor will live! N.O.S will give me the most bang for buck.I just need to do more research. Thanks again for your reply.Jetmech over and out!!!!!!

Similar Threads

  1. Bbc Cylinder Heads
    By 76 SPECTRA in forum Parts 4 Sale
    Replies: 2
    Last Post: 07-17-2007, 08:11 AM
  2. 455 Cylinder Heads
    By 87HARDIN in forum Parts 4 Sale
    Replies: 2
    Last Post: 05-08-2007, 09:49 AM
    By RCB19 in forum Parts 4 Sale
    Replies: 13
    Last Post: 01-15-2007, 09:22 PM
  4. Pro Topline Cylinder Heads
    By WATERFOUL in forum Gear Heads
    Replies: 30
    Last Post: 09-26-2006, 06:54 PM
  5. cylinder heads needed
    By lilrick in forum Gear Heads
    Replies: 20
    Last Post: 09-30-2005, 08:22 PM

Posting Permissions

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