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  1. #1
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    280 rebuild questions about lifespan

    So I have a 280 on a 20" offshore mid. The ID tag says 7700 max rpm. It's got 271.6 hours on it and it's never been cracked. Leak down numbers are horrible. I'm exploring options:

    1) Find a good clean 2.5 complete motor and set the 280 aside for now

    2) Find a good drop-on, but I don't want a 260 and I'm learning that other 2.5's (maybe a PM 225) will require more mods to my mid so other 2.5's aren't a simple drop-on, I'd need to change the adapter and deal with t-stat issues, etc

    3) Build the 280, probably by Jay Smith changing the side pins to top.

    I know next to nothing about these 2.5's. So I'm looking for opinions. I'm never going to be the guy who runs his motor WFO all the time. I live in a county with a MAX on the water speed limit of 30mph. We go 40 to 50 when we can get away with it. I have to go 20 miles to get to water where I can run fast.

    I know the 280's typically get freshened up between 100 and 150 hours. But I've also read that a 280 that's run "normally" can go a lot longer if fed good fuel and oil. How much longer is the question I guess.

    So help me with my options. And do I have more?

    Thanks in advance for your input.

    Trace
    \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\///

    I've bought and sold 24 boats in 28 years. I fix them up and then get bored and look for another. It's a hobby but I've learned a LOT about boats along the way. And I still don't know chit.

    2007 Checkmate Pulsare 24BR / 2021 Mercury 300R SOLD

    2013 Nautic Star 2400 Tournament Bay / 2013 Mercury 250 Pro XS Opti

    Grand Sport Elite with a 280


    .

  2. #2
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    0 - 999 rpm 109.9 hours
    1000 - 1499 1.5 hours
    1500 - 2999 30.8 hours
    3000 - 3999 62.6 hours
    4000 - 4999 17.0 hours
    5000 - 5999 8.4 hours
    6000 - 6999 3.7 hours
    7000 - 7999 0.1 hours
    \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\///

    I've bought and sold 24 boats in 28 years. I fix them up and then get bored and look for another. It's a hobby but I've learned a LOT about boats along the way. And I still don't know chit.

    2007 Checkmate Pulsare 24BR / 2021 Mercury 300R SOLD

    2013 Nautic Star 2400 Tournament Bay / 2013 Mercury 250 Pro XS Opti

    Grand Sport Elite with a 280


    .

  3. #3
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    Jay smith - he will answer the phone and he is well versed . I would suspect - once done you never worry about it .
    If he will accept the build - your in. He has them figured out sorta
    is this on a pontoon boat ? You seem to be spending allot time in 0 999.

  4. #4
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    I bought it on a Allison Grand Sport
    \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\///

    I've bought and sold 24 boats in 28 years. I fix them up and then get bored and look for another. It's a hobby but I've learned a LOT about boats along the way. And I still don't know chit.

    2007 Checkmate Pulsare 24BR / 2021 Mercury 300R SOLD

    2013 Nautic Star 2400 Tournament Bay / 2013 Mercury 250 Pro XS Opti

    Grand Sport Elite with a 280


    .

  5. #5
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    Pull the heads and check your bores. Measure the pistons, if all is good you might be able to get away with replacing the rings. If the Pistons are good and John Marles still installs top pins you can use the same pistons. Inspect the rods, the rod bearings and look at the crank journals.

    You can push the rods and pistons out the back side once you remove the horn and the reed plate. No need to crack the case you can do everything with the engine still on the boat.
    Goodson sells a honing tool for Nic.

    Those motors are simple to work on.

  6. #6
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    Sounds like you don't do a lot of wrenching. I would go with talking to Jay also. He won't steer you wrong.

  7. #7
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    I believe you only have to swap your pan baseplate to run a promax on the offshore mid
    Hydrostream dreamin

  8. #8
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    Quote Originally Posted by TraceF3 View Post
    So I have a 280 on a 20" offshore mid. The ID tag says 7700 max rpm. It's got 271.6 hours on it and it's never been cracked. Leak down numbers are horrible. I'm exploring options:

    1) Find a good clean 2.5 complete motor and set the 280 aside for now

    2) Find a good drop-on, but I don't want a 260 and I'm learning that other 2.5's (maybe a PM 225) will require more mods to my mid so other 2.5's aren't a simple drop-on, I'd need to change the adapter and deal with t-stat issues, etc

    3) Build the 280, probably by Jay Smith changing the side pins to top.

    I know next to nothing about these 2.5's. So I'm looking for opinions. I'm never going to be the guy who runs his motor WFO all the time. I live in a county with a MAX on the water speed limit of 30mph. We go 40 to 50 when we can get away with it. I have to go 20 miles to get to water where I can run fast.

    I know the 280's typically get freshened up between 100 and 150 hours. But I've also read that a 280 that's run "normally" can go a lot longer if fed good fuel and oil. How much longer is the question I guess.

    So help me with my options. And do I have more?

    Thanks in advance for your input.

    Trace
    Youre already in Florida.. Why ship the motor to texas.. Send it to David Dreifort in Vero Beach.. One of the best 2.5 guys in the country, and the fastest.. Best to deal with, best pricing, etc.. Oh and he doesnt treat you like an AHole when you call and tell you how the other guys and the parts they make are terrible.. Very nice guy.

    Look on the high performance boating group on facebook and search his name.. You will see the resume.. Or search this site for keysdave or deeznutz (yes that is really his user name)

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  10. #9
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    I second Dave Dreifort. Leave the block stock. Just freshen it with new pistons. Don’t waste your money sending your existing pistons out to get top pinned. With that many hours I promise you they’re worn out and beating on the bore now
    Erik Kiser

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  12. #10
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    He's had the power head and a new set of Wizard pistons since Thursday

    Thanks for all the good advice
    \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\/// \\\///

    I've bought and sold 24 boats in 28 years. I fix them up and then get bored and look for another. It's a hobby but I've learned a LOT about boats along the way. And I still don't know chit.

    2007 Checkmate Pulsare 24BR / 2021 Mercury 300R SOLD

    2013 Nautic Star 2400 Tournament Bay / 2013 Mercury 250 Pro XS Opti

    Grand Sport Elite with a 280


    .

  13. Likes Capt.Insane-o liked this post
  14. #11
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    your pm is to wrong person

  15. #12
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    Quote Originally Posted by TraceF3 View Post
    He's had the power head and a new set of Wizard pistons since Thursday

    Thanks for all the good advice
    After the rebuild good fuel and oil let it warm up and idle down after a long run well over 200 hours

  16. #13
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    Quote Originally Posted by TraceF3 View Post
    0 - 999 rpm 109.9 hours
    1000 - 1499 1.5 hours
    1500 - 2999 30.8 hours
    3000 - 3999 62.6 hours
    4000 - 4999 17.0 hours
    5000 - 5999 8.4 hours
    6000 - 6999 3.7 hours
    7000 - 7999 0.1 hours
    Put a healthy dose of Mercury quickcleen in the fuel and go run the piss out of it. Given how you've run the motor, I'm banking that it's just stuck rings.

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