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  1. #1
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    1500xs have different pistons than other 140-150hp motors?

    Seems you had some motors with high dome and some with low dome in the inline 6's. I'm just curious if there was a specific piston in the 1500xs compared to a 140 of similiar years etc.
    1990 Viper 140 crossflow
    2011 Sea Hunt 232 Ultra
    1995 Laser 380
    1984 Reaction 19 project.........

  2. #2
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    The 1500xs came with high dome 3 ring power port pistons when new. They are not special, the standard 1500 from this era used the same piston. Now after the 1500 was turned into the 1400 and then the 1150 these motors had low dome pistons in them to help with pre-det.

    The 1500xs has a a standard block with the exhaust ports slightly raised. This block with have a J stamped on the side of the block usually near the serial number.

    I put new high dome 2 ring pistons in my 1500J when I rebuilt. The motor runs strong.

    Conrad

  3. #3
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    Not to hijack this thread, but does anyone know the last year the inline 150 was made.

    Found a deal for one that the guy claims is a 1978. I thought they had became 140s by then.
    1977 Python Inline150
    Carlson CT15/90 RUDE(SWEET AND LOW). SOLD!
    Bentley 200Cruise/90hp Evinrude. SOLD!
    Talon18/150Merc: Getting Upgrades. SOLD!
    77 Viking recored SOLD!
    97 Moomba Boomerang SOLD!
    00 Mirage Ski Racer 2.5 200 SOLD!
    1997 Superboat 454/Magnum





    [IMG][/IMG]

  4. #4
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    Jeff Grigg has said repeatedly that many 1500XSs came with the low dome pistons. He is very knowlegeable on inline Mercurys and has a lot of XS race experience himself. I know for sure that the 76 XS had high domes and have been inside a 78 XS with low domes. Only the 850 came with the 2 ring pistons with the power ports and some people do put the 850 pistons in the 1500s for that reason. There is not a measurable performance difference between the high and low domes on anything other than a full on raceboat and then it is more in acceleration that would take a stopwatch on a race course and measured in hundreths of a second.

    The last year that the inline 6 was labeled 150 hp was 1977. In 1978 it was called a 140. This was not because of any change to the inline 150 but only because Merc did not want to have both a 150 inline and a 150 V6 in the lineup at the same time and new for 1978 was the V6 150 for the first time.

    If you do a search on Jeff_G and take the time to read through his posts I think you will find a lot of helpful information. Where is he any way?
    bama hama

  5. #5
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    Can you put a dome piston in the 1400's (78) if so where do get them.
    Jerry

  6. #6
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    Thanks, that's what I thought.

    Don't know if I'm going to look at this motor or not, but I didn't want to get suckered into buying a 115hp, even if its a good deal.

    Quote Originally Posted by MercNuts View Post
    The last year that the inline 6 was labeled 150 hp was 1977. In 1978 it was called a 140. This was not because of any change to the inline 150 but only because Merc did not want to have both a 150 inline and a 150 V6 in the lineup at the same time and new for 1978 was the V6 150 for the first time.

    If you do a search on Jeff_G and take the time to read through his posts I think you will find a lot of helpful information. Where is he any way?
    1977 Python Inline150
    Carlson CT15/90 RUDE(SWEET AND LOW). SOLD!
    Bentley 200Cruise/90hp Evinrude. SOLD!
    Talon18/150Merc: Getting Upgrades. SOLD!
    77 Viking recored SOLD!
    97 Moomba Boomerang SOLD!
    00 Mirage Ski Racer 2.5 200 SOLD!
    1997 Superboat 454/Magnum





    [IMG][/IMG]

  7. #7
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    Jeff Grigg has said repeatedly that many 1500XSs came with the low dome pistons. He is very knowlegeable on inline Mercurys and has a lot of XS race experience himself.
    I collect and run inline sixes. This is the first time ive heard of low dome pistons in a 1500 L-6. You can put low domes in a motor that came with high domes. But I seriously doubt merc would have put one darn low dome piston in a XS motor. These motors were made for the ultimate speed they could get and low domes would affect some performance on a race boat.

    I just got done rebuilding a J block 1500 and yes it had HIGH dome pistons in it. I have a 1978 1400 and it had LOW dome pistons in it when pulled apart. So I am quite sure the 1400 was more than just a badge name. Everything but the pistons and ignition looked the same tho.

    Many people rebuild the 1500 with low dome pistons, so they dont have to worry about fuel issues as much and low dome pistons are everywhere.

    I know for sure that the 76 XS had high domes and have been inside a 78 XS with low domes.
    Did that 78 XS have the original block (matching numbers) and if it did have the correct J block was the factory seal still on the motor? Many things have happened to these motors over the last few decades.

    Conrad
    L6fan57-88

  8. #8
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    Quote Originally Posted by 97 TWISTER View Post
    Can you put a dome piston in the 1400's (78) if so where do get them.
    Jerry
    All of these engines have dome pistons. The high dome is a little less than 1/8" higher than the low dome. If you did not have the two side by side you would not be able to tell the difference unless you had the measurements. I think you would waste you money by converting a 78 140 to high domes and you would be more likely to detonate and burn with high domes.
    bama hama

  9. #9
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    I am currently putting high domes in a 1400 block that I have. I hope to make a special 12 inch mid for it. Yes its on a light boat and yes I think it will help. I will port it to xs specs and it will basically be a 1500xs with ADI.

    But most people with normal boats will not notice the diff. between high and low domes and will be better served by low domes.

    I run 100LL to be safe with high domes.

    Ill add a pic of the pistons later
    Conrad
    L6fan57-88

  10. #10
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    Here are low vs high dome
    Conrad
    Attached Thumbnails Attached Thumbnails LOW.jpg  
    L6fan57-88

  11. #11
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    Mercnuts is right, the later XS motors came with low dome pistons. I have a late 78 1500xs and it has never been apart and it has low dome pistons in it. I also have some replacement power heads that have never been run and they have the low dome pistons in them, they were made towards the end of the 70's. They are all J2 blocks btw. As for the 140, it is just a 1500 with different stickers as all the inline motors had low domes by that point to deal with crap gas. The only motor I have noticed a difference between high domes and low domes was the 650XS.

  12. #12
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    Thats good info to know! They must have been only making low domes by 77-78 time frame and that was a transitional time.
    Thanks
    Conrad
    L6fan57-88

  13. #13
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    How about the moly rings? We used to use them exclusively in the 150 J blocks. Probably got no benefit other than is sounded good to say we had them.
    18 Talon/2.4 carb SOLD
    26 Deck Boat/250 Merc

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