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  1. #1
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    Saving a 2.5 crank shaft

    I have a new project. A boat with a 175 sportjet, or had one. Block is gone, but I have everything else. Problem is the crank shaft has been sitting in the boat for years and has surface rust on it. is there a way to save it? The journals has rust spots on it. One of the few parts unique to the sportjet is the crank. and they are getting hard to find.

  2. #2
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    can you change the input shaft on the pump to that from a mercury gear case? then just run a regular mercury crank

  3. #3
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    nope, Mercury found that without the drive shaft to take the torque pulse, it wiped out the splines in the crank shaft, so they change the splines to keep it from failing. So they ended up with a unique crank shaft for the sport jet. Its a real pain in the butt if your trying to save one.

  4. #4
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  5. #5
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    can't get to the link

  6. #6
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    Quote Originally Posted by Poky View Post
    can't get to the link
    This was the link. Brand new.
    Attached Thumbnails Attached Thumbnails Sportjet screen shot.JPG  

  7. #7
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  8. #8
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    I found that one, Thank you. I think he has it on ebay too. My last jetboat, I had Wintech build me a power head. I bought this boat to get the better jet pump parts out of, but the boat has only 47 hours on it. So after bring it home Saturday and getting the snow and ice out of it. I decided that I'd like to fix it. From what I can tell from what the boat is telling me, is that someone removed the oil pump, then I'm guessing they sold it, and the next person didn't realize they needed to mix the gas. one busted rod, #1 and #3 is badly scored. I want to work at finding a old 175 repair it and swap out the crank myself. More hands on than the last one.

  9. #9
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    Can u take a 25in shaft or 30 and have it cut and respond? Just curious

  10. #10
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    I did a 175 sport jet before, I needed to find a sport jet crank. the crank for the 240 is a 3 liter, I would think its still the same spline. before I work at changing the shaft for the jet pump, I would work at finding someone from mercury that worked on the project, I knew one of the guys that worked on the 90/120, be he left before they did all the testing on the V6.

  11. #11
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    Surface rust........just polish it...... Check with Mike......all other things that can screw up get over looked........A small surface blemish is the last thing that will blow a motor..........

  12. Likes OnPad, Aaronhl liked this post
  13. #12
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    I'm going to give it a try and see how good or bad it comes out

  14. #13
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    Well I didnt wanna be the first person to say polish so Im glad somone else did...I just finished polishing rust of a couple crank journals and will be putting it in an engine soon, I decided to do that because polishing with sandpaper and a shoe string actually made it look pretty good, plenty of youtube videos about that


  15. #14
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    I'm going to use eomery cloth sand paper. what grit should I start with and how find to get a nice polish?

  16. #15
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    I used 400 on one with some chatter mark's in it.
    Probably should of thrown it away, but it's lasted acouple years now. Had to work pretty hard to get almost .001 knocked off. Really hard metal. I think I probably used some finer to finish it up 600 800 1200 wasn't really worried about it being perfect, just wanted to keep it round and smooth it out a bit. I was hoping the rod bearing would finish polishing. I've seen the clutch bearings (needles) on my chainsaws run on some pretty haggard surfaces and hold up.
    Last edited by OnPad; 01-24-2022 at 09:49 PM.

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  1. Crank shaft drive shaft splines.
    By gwalt584 in forum Technical Discussion
    Replies: 5
    Last Post: 07-05-2005, 09:55 AM

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