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Thread: 502 EFI rebuild project

  1. #1
    kevnmcd
    Well, since Beer-30 asked in another thread I thought I would start a thread on my project. For some reason I lost a ton of power and compression over this last season so I decided to take it out and tear it down. The motor is a 502 Mag EFI. I am not the most knowledgable on this but I have a buddy that is and he is helping me do it. I was surprised when I found out it was a Gen VI and not a V! Based on the year of the boat and the Mercruiser Serial #, everything pointed to a Gen V and I was going to convert it to a Gen VI. Anyway, here goes.....
    How many have pulled your motor with one of these?
    http://www.lasvegas***boats.com/iB_h...-IMG_1808a.jpg
    I was expecting to see either a burnt valve or some bad springs but didn't find either.
    http://www.lasvegas***boats.com/iB_h...-IMG_1824a.jpg
    Well, maybe a some cracked pistons or bad rings???? Doesn't look like it.
    http://www.lasvegas***boats.com/iB_h...-IMG_1825a.jpg
    About this time we were scratching our heads trying to figure out what the problem was. It wasn't until we turned over the block to take the pan off that we found our problem.....I wonder if this is it???
    http://www.lasvegas***boats.com/iB_h...-IMG_1826a.jpg
    It seems that when they assembled this motor somehow an extra rod nut was left in the pan. It just took 10 years and the perfect wake at the right time to send this nut up into the cam. It must have gotten stuck in there for a time or something. It tore up a lobe pretty good and busted another lifter, too. Oh well....time for more HP!!!!
    I purchased an upgrade kit from Crockett marine engines which should bump the HP up to around 510-520. Block and heads will be going into the shop next week for all the machine work and I should be putting it back together at the end of this month. More to follow.

  2. #2
    Infomaniac
    Cool stuff man. We routinely pull engines with a fork lift. And occationally dig up some soil with the fork lift. LOL

  3. #3
    Shallow Minded
    Good thread, keep us posted on the rebuild. Those #'s should be easily attainable. And you weren't messing around with the cherry picker... LOL.

  4. #4
    kevnmcd
    Couldn't rebuild it without adding a little bling to it.
    http://www.lasvegas***boats.com/iB_h...-IMG_1843a.jpg

  5. #5
    Wild Horses
    Hey Kevin,
    Welcome to the Horsepower club.
    I always pull my boat motors with a frontend loader.

  6. #6
    kevnmcd
    Hey Kevin,
    Welcome to the Horsepower club.
    Thanks. Probably still not in your range but definately better than before!

  7. #7
    Beer-30
    You Go, boy!
    Hey, the backhoe is just as good as a tow truck. I have always preached that hydraulics do lots of work for us. Atta boy!
    I think the Crockett kit will work good for you. I would have done it if I ended up with a Gen V or VI, but I ended up with a VII. I envy you.
    Keep it up!

  8. #8
    kevnmcd
    You Go, boy!
    Hey, the backhoe is just as good as a tow truck. I have always preached that hydraulics do lots of work for us. Atta boy!
    I think the Crockett kit will work good for you. I would have done it if I ended up with a Gen V or VI, but I ended up with a VII. I envy you.
    Keep it up!
    Thanks. I will post pics as I go. Should be assembling between xmas and New Years. Here are a few of the parts I have so far.
    http://www.lasvegas***boats.com/iB_h...0-P1000498.jpg

  9. #9
    Wild Horses
    Looks like a good assortment to me.
    And have a fun Christmas vacation.

  10. #10
    bubbletop409
    Are you changing or upgrading your cam and valve train during your rebuild? If so, what are you planning on going with? I have a 26' Eagle with a HP500EFI and will be following your rebuild closely, thanks, Larry.

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