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New tohatsu EFI 9.9/15/20 - conversion 9.9 to 20?

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  • #16
    The 3RU (9.9), 3RT (15), and 3RS (20) are NOT the same ECUs. Duh.
    If you remove the restrictor on the 9.9, it will run horribly lean.

    The 15 also uses a (different) restrictor (3RT035360M) from the 9.9.
    To convert from 9.9 to 15, you change restrictors, and change ECUs.
    To convert to 20, you remove any restrictor, and change the ECU ($900 in parts plus labor).
    Last edited by pvanv; December 5th, 2018, 05:53 AM.
    Paul
    Buffalo NY USA

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    • #17
      Come on people, everybody knows you can DOUBLE an engine power by simply changing the jets in carb, and turning a screw on the block...

      Even changing a ECM and removing a restrictor plate can't be all of it. Other differences like Heads, Valves, Camshafts, Intake Manifold, WOT RPM range, would be needed to Double the HP of a given displacement.

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      • #18
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        Originally posted by jimmbo View Post
        Come on people, everybody knows you can DOUBLE an engine power by simply changing the jets in carb, and turning a screw on the block...

        Even changing a ECM and removing a restrictor plate can't be all of it. Other differences like Heads, Valves, Camshafts, Intake Manifold, WOT RPM range, would be needed to Double the HP of a given displacement.
        As with all outboards from all manufacturers, they are built in families. The MFS9.9/15/20E is one such family. The ECU is the detuning factor. The motor is designed and built as a 20, and then detuned. The air restrictor is needed to match the ECU. So, YES, changing the ECU and restrictor DOES make the change. No change to head, valves, cam, intake manifold. Just as the carb is the determining factor for the MFS2.5/3.5, and also for the MFS4/5/6, as well as the MFS8/9.8. Yes, it DOES make the change.
        Paul
        Buffalo NY USA

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