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  1. #1
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    Mercury I6 Exhaust Tuners

    Hey Folks,

    I was fooling around with some of my old inline parts and noticed some differences with the exhaust tuners. The first pic is from an earlier I6, I believe a 1150, the second is from a later ADI 115.

    The tuner on the later model is noticeably longer than the one from the earlier model.

    I have a complete mid 70's 1500 which has a tuner identical to the one from the early model 115. The tuner casting on my 1500 has cracked into pieces and as such I would like to replace it.

    Any opinion on which tuner is better for this application? How might the power band be affected if I swapped to the later model ADI 115 tuner?
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  2. #2
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    Longer newer tuna ....better. Better in salt too.

  3. #3
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    Quote Originally Posted by Dave S View Post
    Longer newer tuna ....better. Better in salt too.
    Any thoughts on how the power band might shift? The casting quality on the newer tuner certainly looks superior to the old. Just hope I can split this lower given the level of corrosion on the bolts....

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    If you have a short shaft I could see pulling apart. If just a long change the whole thing.

  5. Likes Mark75H liked this post
  6. #5
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    A longer tuner will usually be more effective in a lower rpm, it may also broaden the rpm range where it is effective. Being the later 115 is similar, but not identical to the earlier 150, running it might be the only way to find out

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    I wonder if it would be wise to run the carbs from the newer 115 ADI in combo with the 115 ADI tuner?

  8. #7
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    Quote Originally Posted by NoRdO View Post
    I wonder if it would be wise to run the carbs from the newer 115 ADI in combo with the 115 ADI tuner?
    Well that's a good question. As there are differences between the engines besides the tuner, the 150s would have higher dome pistons. In 1984 Merc changed the piston to a lower dome. How it affects compression and/or port timing I don't know. Some people say the 115 have fewer reeds on some cylinders. Looking in my parts book for my old 1984 115, all 3 reed blocks were the same and the reeds said 10 leafs.
    My suggestion is you can try both, but keep an eye for leanness. Of course, you also need to aware the primary pickup timing may change too.
    Post 74 inline 6s have the back drag feature on the carb. disable that, as todays gasoline will end up being too lean during its operating parameters.

  9. #8
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    There are a few differences between the 1500 and ADI 140/115. The 10/8 reed blocks, different carburetors, low dome pistons, different ignition and slightly lower port timing. If it were mine, I would use the later model 115 ADI tuner, the original 1500 carbs with 0.082 or 0.084 jets, plug the back drag lines on the carbs, set timing to 19 degrees maximum, 40-1 non-ethanol fuel and prop it to turn 6k wide open. The later model lower unit will perform better as well. The 140/115 ADI was supposed to be the best of the bunch as far as all around usage.

    There was a re-rating of the motors sometime around 1982/3. The 140 became the 115 and the 115 became the 90. The 140/115 uses the low domes (A9-A11 pistons) and 115/90 uses the high domes (A12-A14). The parts lists on the online sites can be helpful when determining at what serial number this happened. Most of the online parts lists sites have been updated to show low domes in the 1500s. People that know better than I have reported seeing low domes in the late 70s due to poor fuel economy and burned pistons. I didn't get involved until the 2000s so I can't guarantee this is 100% accurate.

    Your mileage may vary...
    Last edited by CrayzKirk; 02-21-2018 at 05:57 PM.


  10. #9
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    The prop rated serial numbers started
    90hp
    US 5299506 and above
    AUS 8060545 and above

    115hp
    US 5829464 and above
    AUS 8071135 and above
    CAN 7171253 and above


    AS for the prop rated 115 being a crank rated 140? No, there are differences
    AS for the crank rated 115 becoming the prop rated 90? I don't think so


    WOT ranges
    140 crank rated 5300 - 5800
    115 crank rated 5000 - 5500
    115 prop rated 5000 - 5500
    90 crank rated 4500 - 5000
    90 prop rated 4500 - 5000

    Factory parts catalogs would shine light on the parts differences.
    In my 1984 90/115 parts catalog showed the 115 having 10 reeds on all sides of the 3 reed blocks and the 90 having 8
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    Last edited by jimmbo; 02-21-2018 at 06:38 PM.

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