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  1. #1

    How do you do an frame rebuild 12v71

    I am curious. I've seen lots of posts regarding rebuilt engines that were done in the boat. My question is how do they actually achieve it? How do they lift the heads off? How to get adequate access to the crankshaft underneath etc? I'm looking at the engine room on my 1984 61MY now and trying to visualise how it all might be done. How long might each section of work take to accomplish?

  2. #2

    Re: How do you do an frame rebuild 12v71

    The pan drops and I believe is 2 sections. That's the power access.

    The heads are heavy but come off. As does the rest of the top end.

    It's a lot of work but the boat was designed for it.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  3. #3

    Re: How do you do an frame rebuild 12v71

    On some boats the shaft must be disconnected and the rear half of the engine is jacked up to allow clearance to drop the pan and access bearings etc

  4. #4

    Re: How do you do an frame rebuild 12v71

    I have a jib crane and winch mounted in my ER. Makes removal of the 230lb head, Inter Cooler, and blowers a snap. Removal of the upper oil pan (130lbs), gives good access to the lower end. The Cam shafts slide out.

  5. #5

    Re: How do you do an frame rebuild 12v71

    I don't suppose you have photos of any or all of this?

  6. #6

    Re: How do you do an frame rebuild 12v71

    No pics means it didn't happen

    🤣
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  7. #7

    Re: How do you do an frame rebuild 12v71

    In 1980 I was experiencing a number of mechanical problems with my 8-71Ns and Allison transmissions which were then 16 years old. My work schedule made vacations tight. And I soon learned that if something broke in the Bahamas it wasn't going to get fixed until we got back to the States. After two single-engine returns I had had enough.

    I got bids from several Detroit Diesel shops to remove and rebuild both engines and transmissions. I ended up taking the boat to Jacksonville Beach, FL, storing it for a couple months at a marina and having the work done there. I believe this work included a one year warranty. This brought my engines up to 1980 specs which reduced oil leakage considerably. Today would probably be even better. These engines were reliable for the next 15 years (although not perfect from a performance standpoint, but that's another story).

    While an in-frame rebuild can be done, I observed the procedures on my engines and I am convinced that you can not get the same quality rebuild that you will in a properly equipped shop with all the specialized tools. Just for one thing my engines were run in on a water dynomometer up to full speed for an hour or so. I saw someone else's engine fail while this was being done. This got fixed in the shop before the engine was installed.

    I have also found that if some part fails on one of my engines the other engine is likely soon behind. Better to bite the bullet, get everything done right and enjoy your boat for the next few years.

    Of course, on my series, the 50-53-58MY, the engines are accessible through salon hatches. A more complicated removal could require more thought.
    Jim Grove, Fanfare 1966 50MY Hull #22 (Delivered Jan. 7, 1966)

    "LIFE IS JUST ONE DAMNED THING AFTER ANOTHER." Frank Ward O'Malley, Journalist, Playwright 1875-1932

  8. #8

    Re: How do you do an frame rebuild 12v71

    Looking at my 8V71 in the 53 I don't see how can do the bottom work without raising the engines at least a foot, there is just no room Between the stringers and the block So at that point you may as well pull them out
    Pascal
    Miami, FL
    1970 53 MY #325 Cummins 6CTAs
    2014 26' gaff rigged sloop
    2007 Sandbarhopper 13
    12' Westphal Cat boat

  9. #9

    Re: How do you do an frame rebuild 12v71

    Quote Originally Posted by Pascal View Post
    Looking at my 8V71 in the 53 I don't see how can do the bottom work without raising the engines at least a foot, there is just no room Between the stringers and the block So at that point you may as well pull them out
    Interesting thread. You have little room under your motors, but I know you’ve got tons of overhead room. On my boat, I’ve been wondering how the air boxes would come off with just inches between them and the overhead and galley above. I don’t know who would get those outboard heads off either; I just know who it’s not gonna be. Kinda tends to make me throttle back some.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  10. #10

    Re: How do you do an frame rebuild 12v71

    A customer had a local DD shop in Orlando rebuild both 671tib's out of the boat so they could line bore and tank the blocks. 200 hours later their both toast. One had 2 kits and a head replaced by a shop in jax 2 months ago and now it's been found that both engines have the wrong heads, wrong kits and other issues. I'm sure a lawsuit will determine the final outcome.

    The previous inframe lasted 3500 hours and they did the rebuild before any failures to ensure reliability.

    It's who does the work not where they do it. Jacking up an engine to get to the bottom is no big deal
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

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