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8v71 questions?

Discussion in 'Chris Craft Roamer Yacht' started by gibson36, Nov 3, 2011.

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  1. gibson36

    gibson36 Member

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    So can I turn these over by hand is that possible? I need all new batteries
    and since its a 32volt system I don't want to buy 8 batteries till spring , no point in them
    sitting all winter also what motor spins what direction?

    Thanks
    Justin
  2. Marmot

    Marmot Senior Member

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    Never met an engine yet I couldn't turn over by hand ... with a long enough lever.
  3. K1W1

    K1W1 Senior Member

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    Hi,

    With DD 2 Strokes turning by hand in either direction is fine, they are known to be able to run backwards in certain situations.

    Just make sure the Fuel is off which ever way you crank them by hand.

    When I was an apprentice I was moving a Tractor Unit with an 8V 71 in her, I stopped and as the stop solenoid wasn't working I let the clutch out in gear to stop her, I clutched in a bit early and she coughed back into life with a big puff of smoke out the air cleaner inlet while sucking the smoke that had come out back down the exhausts according the my foreman who seemed to be traveling towards me in some strange way some distance above the ground.

    A quick wrenching of the Emergency Stop lever and things quietened down somewhat.
  4. dennismc

    dennismc Senior Member

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    8-71

    Just as long as you don't think that will temporarily save you buying batteries for starting they are not easy to start by hand cranking..
  5. Capt J

    Capt J Senior Member

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    This is UNTRUE, you can only turn DD's by hand in the rotation that they normally run in, otherwise you will snap off the raw waterpump keyway/gear.

    With that taken off, then they will even run in each direction, (albeit not very good with the blower spinning backwards). A breaker bar and socket on the crankshaft end will turn them.
  6. gibson36

    gibson36 Member

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    okay and what way should i be turning what motor
  7. dennismc

    dennismc Senior Member

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    That must be unique to 8-71's, my 12-71's and 6-71's have splines drive for the raw water pumps.
  8. dsharp

    dsharp Senior Member

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    It depends if both engines turn the same and 1 reverses in the reduction gear. Most boat engines turn outboard looking at them from the rear. Personally, I would buy batteries and run them occasionally. I haven't seen much "good" happen from letting machinery sit.
  9. K1W1

    K1W1 Senior Member

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    Hi,

    CaptJ, You could do with some comprehension lessons if you think my words mean something different to your use of them.

    I wrote that they can be turned in either direction and it is possible for them to run in reverse rotation.

    You wrote that this was UNTRUE and then went on to say they could run backwards.

    Seems like the same message to me.

    The use of a socket and breaker bar should only be done in the direction that tightens the bolt that secures the front pulley, this will be Clockwise when viewed from engine front. Going the other way might loosen the bolt.

    This is also not always as straight forward as it sounds as in applications I have seen there is often something driven off this pulley that will need to be removed to give access to the securing nut in the first place.

    As for the water pump failure, I guess anything can fail at anytime so maybe your time was up for it to fail.
  10. CaptPKilbride

    CaptPKilbride Senior Member

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  11. dennismc

    dennismc Senior Member

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    Safety first..it could kill you...
  12. gibson36

    gibson36 Member

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    yea I thought of that and figured hell with it and ordered all new batteries should be here tonight keeping my figures crossed that the girlfriend wont see the account balance at the bank ...lol
  13. Capt J

    Capt J Senior Member

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    I wrote that you can just turn them, by hand, either way is untrue. According to Western Branches head mechanic, if you turn them the wrong direction, the gear driven waterpump will snap the keyway or gear, because it is not able to turn backwards. I have never snapped a waterpump or anything of the sort. I was not stating the part about them being able to run in either direction that you mentioned was untrue.

    This was my intial post "This is UNTRUE, you can only turn DD's by hand in the rotation that they normally run in, otherwise you will snap off the raw waterpump keyway/gear." The raw water pump is gear driven by the flywheel on most 8v71/12v71's. It has nothing to do with the crankshaft bolt loosening, and there is rarely anything attached to the front crankshaft pulley on marine applications I've seen. Once in a while someone else has attached the pressure pump for a stabilizer system or something like that via a belt to the crankshaft pulley.

    so PLEASE get some lessons in reading comprehension skills and understanding of the English language before you blast me.
  14. dennismc

    dennismc Senior Member

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    More popcorn please...
  15. K1W1

    K1W1 Senior Member

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    Hi,

    Unless things have changed since I last saw one the Flywheel is the big round thing at the back that the starter normally uses to rotate the engine during starting, the Flywheelitself is used to drive the Transmission via a clutch, torque converter, Flexible coupling, Jackshaft.

    If your head mechanic told you this is what runs the Raw Water Pump I wonder what he thinks the gears in the housing between the Flywheel and rear of the engine are for.

    My words about taking care not to loosen the Bolt in the end of the crank when cranking the engine were not directed at you as such but as an aside to a preceding comment where the use of a Socket and breaker bar were suggested.

    From your latest post - I should point out that a Pump provides flow not pressure. It is the resistance to flow that creates the pressure even in your world. It's good to see that it was someone else that did that not you.
  16. gibson36

    gibson36 Member

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    Not to ruin everyones this and that but I got my batteries

    And after 3 years on the hard hooked it all up and ..........boom they both turned right over no big deal at all I'm happy with that ... please feel free to continue your conversation just thought I would share ....

    thanks again ...
    Justin
  17. dennismc

    dennismc Senior Member

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    Hope you flooded the raw water pump intakes...
  18. gibson36

    gibson36 Member

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    did not try and start just a quick turn not enough to tear anything up just wanted to make sure they were not locked up as its a new to me boat. but had to make sure that part was good before I started on the rest of the project ..
  19. Capt J

    Capt J Senior Member

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    Chances are that if they haven't run for 3 years that they're going to need cylinder kits. Generally the cylinders get corrossion and rust in them, when you get the motors running, the rings will then usually knock the corrossion/rust off of the cylinder walls and you'll lose compression. I would take the airboxes off and look in the cylinders and see what they look like, there's 2 bolts for each cylinder so you can check all of them in a few hours or less.
  20. gibson36

    gibson36 Member

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    okay that's great advice I will do that in the spring not really gonna mess with it till then got a ton of other things to work on .. striped out the salon today and started sanding everything down looking to have the interior 90% by the time I start trying to get the motors up and going ....is there anything else that should be checked other than cylinder kits ? ? the motors have 830 hours