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  1. #1
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    May 2021
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    Buffalo, NY
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    6

    Tried to convert my 2021 Mercury 50hp to 60, and failed...

    Are they on to us? I removed the restrictor and took it out for a test run, with the restrictor in the boat maxed out at 5800rpm. With the restrictor removed it zipped right past 6000rpm and hit the rev limiter, at least that’s what I thought. It beeped and wouldn’t rev over 4000 rpm. I thought that was odd for a rev limiter. I shut of the engine and restart and it revs up to 6000 but of course shuts down again.

    Fast forward to today when my new prop came in, so I swapped the prop, and my son and I go for what was supposed to be a successful rip, hoping to hit a whopping 25mph! (It’s a Sun Tracker Bass Buggy 16, so it ain’t fast) and the same thing happens, but at 5500 this time, so yeah, not the rev limiter. I have VesselView Mobile so I check that and get a code for air flow too high. Do I need a 60hp ECU too? Is this a new thing? I did a lot of research before this and there isn’t much out there to research, but no mention of error codes. I really don’t want to buy a new ECU, but I might. The other option is to just put the restrictor back in and have a couple less MPH on the rarely visited top end. The new prop is much better at all other RPMs, I just would have liked a free 60hp engine (minus the $150 prop)

    I have a video of my shenanigans, it’s somewhere in my boat review. Around the 5:45 mark...

  2. Member tcesni's Avatar
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    Apr 2005
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    Smith Mountain Lake, VA and a cottage in Ontario
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    #2
    Back when Optimax 90 hp owners would convert to 115 hp it required reflashing the ECU.

  3. Member
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    May 2021
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    Buffalo, NY
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    6
    #3
    I realized there is a better place for this, so I posted it in the Mercury 4 stroke section. I think I posted it here because there were many threads that came up from this particular forum for the smaller Mercs.

  4. Member
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    Apr 2012
    Location
    Insomnia, near Seaford Delaware
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    35,449
    #4
    With more air you must have more fuel. If it's a 2 stroke you need bigger caburetor jets. If it's fuel injected you may need bigger injectors or a reflash. No, I don't own a Mercury at this time.

  5. Member
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    Mar 2013
    Location
    Michigan
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    1,296
    #5
    I've got a 60HP that performs the way a 60HP should. There seems to be way more risk than reward tinkering around with an outboard, but that's just my opinion.

  6. Member
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    Nov 2018
    Location
    Texas
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    1,962
    #6
    if you wanted more horsepower you should have paid for it.

  7. Member
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    Jun 2018
    Location
    Lancaster, Ohio
    Posts
    136
    #7
    Remove restrictor and purchase the 60 hp ecm and your done. Ecm is about $600-700. Buddy of mine did it on his Tracker Pro 170. Last year. Runs great. The new ecm increase fuel amount for the added air. Between the new ecm, SS prop and raised the engine up one hole he picked up 5-7 mph depending on load.

  8. Member
    Join Date
    Oct 2012
    Location
    Pelham, AL
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    2,148
    #8
    You may have voided your warranty.
    2015 Ranger RT188 DC; BassCat Storage Box; Mercury Optimax 115ProXS;
    19" Spitfire X7; Vessel View Mobile; Minn Kota Ultrex 80; GForce Handle;
    TM Eliminator; Helix 7 G2N SI Combo F/R; HydroWave KVD; BBT 4" Angled Bow Mount; Durasafe Locks for Electronics and Ultrex;
    Twist Step Boarding Ladder; EZEE Step ES1; BAC RAC Rod Storage; Motor Mate Transom Saver

  9. Member
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    Jun 2019
    Location
    Illinois
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    837
    #9
    Sometimes it’s costly to learn internet advice to modify something is pure BS.😳

  10. Member
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    Dec 2015
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    Alabama
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    21,475
    #10
    I never understood why they charge much more for the more powerful engine. It probably costs more to make the 90 than it does the 115. That restrictor costs money. The 90 should cost more.

  11. Member
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    Jun 2018
    Location
    Lancaster, Ohio
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    136
    #11
    E-rude_dude.....no BS...the Merc 50-60 4 cyl 4s is exactly the same engine. The only difference is the restrictor and ecm.

  12. Member
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    Jun 2019
    Location
    Illinois
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    837
    #12
    Quote Originally Posted by SWA12 View Post
    E-rude_dude.....no BS...the Merc 50-60 4 cyl 4s is exactly the same engine. The only difference is the restrictor and ecm.
    ECM is a big difference. Electronic motors can’t function with out programming to tell them how to mix fuel, combust that mixture, and exhaust that combustion. It’s not like the old days when you could change a few parts and get more HP.

  13. Member
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    Jun 2018
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    Lancaster, Ohio
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    136
    #13
    Agreed..change the ecm and remove restrictor, you have a 60hp engine. No argument. It's been done and works flawlessly and is even confirmed by Mercury vessel view mobile as a different engine code.

  14. Member
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    Nov 2010
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    Ontario, Canada
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    2,770
    #14
    that is how my 75 Optimax changes to a 90 or even 115, no restrictor and modify the ecm. I think Mercury put an end to the company that modified them.

  15. Banned
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    Aug 2004
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    Hubbard, Ohio
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    12,389
    #15
    I know when it comes to small outboards, it can't be done with Mercury's. To make a 9.9 2 stroke Johnson a 15hp, you put a 15hp carb on it. It works great! Added 7 mph & about 800 rpms. Did same thing with a 9.9hp 2 stroke Mercury,..... and nothing! NO DIFFERENCE AT ALL.