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  1. #1
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    Whats needed to turn a 225 opti into a 250xs ?

    Ok im not up to speed on what's needed to turn a 225 opti into a 250xs? I have several 3.0 litre EFI engines which I've taken from 225-250 hp to 300 x with port timing, 300x head, 300x induction and ecu but zero exp with Opti .
    I have a few opti powerheads here and I'd like to make a 250xs .The ex port is 1.80 height on this 225 opti. What is needed that I missed on this list
    250xs ecu
    different fuel injectors ?
    Difference in heads and comp from 225 to 250xs ?
    Also are those humps removed in a 250XS exhaust chest as I do to make a 300 x

    Thanks
    Larry

  2. #2
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    I know the blocks are the same it’s heads and ecu and tracker valve spring fuel pressure is up from 80 to 90 psi I don’t know if Merc still sells spring separate from tracker valve assembly the exhaust can mod will help too hope this helps
    Last edited by MrG; 03-14-2022 at 05:57 AM.

  3. #3
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    300x has domed pistons & heads larger throttle valve and inj ,higher fuel pressure 100 psi and ecu re mapped with like 32 deg timing I have 2 ecu’s been holding on for a wile but the last 250xs that Merc offered in 2019 as a drop on power head for 6 k were a steal did a swap for 225 opti cut the exhaust can at glue line and installed new bushings and mounts an picked up 10 mph on the wood an 2.5 gl at 4K rpm on a 32 contender with the same props have to say the 225 had 3200 hr on them and they still ran good customer said his fuel consumption was down to 1.9 at cruse he new the engines were getting tired from allThe weekend runs to Bimini and he didn’t want to get fuel in the islands cuz you don’t really know how good it is
    Last edited by MrG; 03-14-2022 at 05:50 AM.

  4. #4
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    Quote Originally Posted by MrG View Post
    I know the blocks are the same it’s heads and ecu and tracker valve spring fuel pressure is up from 80 to 90 psi I don’t know if Merc still sells spring separate from tracker valve assembly the exhaust can mod will help too hope this helps
    These are really easy to mod... You simply remove the diaphragm cover, drill & tap it for a screw that you polish the end and use a locknut with Loktite to keep it from coming out. This way you apply additional pressure to the spring to "fine-tune" both your air & fuel pressure to get the necessary burn on the plugs and power needed. Optis respond very well to enrichment, making killer midrange power all the way to the rev limit. Hope this helps!
    David "Tango" Wilks

    Current boats: (Not All Running...LOL)
    18' VT-Rocket Bass Boat: 2.5L 280 Mercury
    21' Eliminator Daytona: Stripped and Possibly For Sale!
    24' Skater: Uncut, Not Rigged and Possibly For Sale!
    30' SeaRay 290 SunSport SLX: twin 3.0L Duramax diesels & Bravo3 drives
    52' Sunseeker Predator twin Volvo-Penta IPS900 diesels

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