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  1. #1

    How much raw water?

    Can anyone estimate how much raw cooling water an 8V71 and/or 8V91 uses? Was talking to someone who has the emergency setup where they can switch from outside water to pumping from the bilge..... Was wondering how many GPH we are talking. Yes, I realize RPM makes a difference, so lets say 1500-ish.... Thanks.
    1978 53' Motor Yacht "LADY KAY V"
    Hull number 524
    Chesapeake Bay
    https://ladykay.blog/lady-kay-v/

  2. #2

    Re: How much raw water?

    You mean pumping out the bilge?
    Prometheus
    1978 53' MY Hull #529
    Viera, FL

  3. #3

    Re: How much raw water?

    Sounds like a good idea, but a crash pump would be better, although hard to find in diesel. If you empty the bilge and overheat the engine you now have another big problem.
    JMooney
    61 MY 1983 #341
    “Jerrie”
    Miami , FL

  4. #4

    Re: How much raw water?

    I ve never been a huge fan of that set up as it requires someone to physically be in the ER, with likely high water level, stuff floating etc. and then someone has to stay there monitoring the water level other wise you end up dead in the water.... it should be a last resort option but the safest things is to have decent bilge pumps. I wouldn’t use anything less than the rule 3700 on our boats. Right I only have 4 of them but will be adding a 5th one. That will bring total capacity to 18850 GPH... yes I know the 3700 rating is zero head full voltage but even 3000 each will be pretty efficient. Plus every second count and the electric pumps will kick in right away.

    Crash pump are great but storage is an issue and then deploying them takes time.

    The boat i run has a number of 3700 plus a 240v electric pump with manifolds to three areas. That’s great as long as one of the gensets is still on line, you have time to go down to the ER and prime the thing...
    Pascal
    Miami, FL
    1970 53 MY #325 Cummins 6CTAs
    2014 26' gaff rigged sloop
    2007 Sandbarhopper 13
    12' Westphal Cat boat

  5. #5

    Re: How much raw water?

    My DD manual references an optional bilge pump attachment, although, it isn't for cooling, just to pump.
    Prometheus
    1978 53' MY Hull #529
    Viera, FL

  6. #6

    Re: How much raw water?

    Quote Originally Posted by Pascal View Post
    I ve never been a huge fan of that set up as it requires someone to physically be in the ER, with likely high water level, stuff floating etc. and then someone has to stay there monitoring the water level other wise you end up dead in the water.... it should be a last resort option but the safest things is to have decent bilge pumps. I wouldn’t use anything less than the rule 3700 on our boats. Right I only have 4 of them but will be adding a 5th one. That will bring total capacity to 18850 GPH... yes I know the 3700 rating is zero head full voltage but even 3000 each will be pretty efficient. Plus every second count and the electric pumps will kick in right away.

    Crash pump are great but storage is an issue and then deploying them takes time.

    The boat i run has a number of 3700 plus a 240v electric pump with manifolds to three areas. That’s great as long as one of the gensets is still on line, you have time to go down to the ER and prime the thing...
    I saw the tables that calculate how much water comes in for various sized holes. I think you are better off practicing ditching.
    Prometheus
    1978 53' MY Hull #529
    Viera, FL

  7. #7

    Re: How much raw water?

    I have an old Jabsco emergency pump on my stb main. Belt driven with a lil lever you push over to engage. It uses the impeller from a 8V71.
    I recall it was rated at 60+GPM.
    The one time I used it was 16 years ago. It moved a heck of a lot of water quickly. Side Thruster anyone?

  8. #8

    Re: How much raw water?

    Honestly, the idea of a valved crash pump on our boats is a non-starter for me. As was pointed out, you need someone to monitor the situation. How many wives or kids are comfortable in an engine room underway with everything in the pink? How many of the above can effectively con the boat and handle the radio if you are the one in the ER?

    As also brought forward, the volume of water from even a tiny hole is astounding. Hopefully, such a leak is a blown-off hose or some other concentric opening when an oak or rubber plug can be be driven. I unsuccessfully used a seat cushion to stem the flow after impacting something big in a wooden boat many years ago.

    Having great bilge pumps is, indeed, essential. But unless they are clustered in the right spot, you've only really got the one or maybe two when the first stringer is over-topped.

    That no one solution works for everyone all the time is the only certainty. First priority should be your safety and communications gear. Second is having what you need within easy reach to slow a geyser; e.g., plugs, mallets, rescue tape, lights, etc.

    As for me, myself and I, Aslan carries two submersible pumps. One is a garden variety I use for things like swapping coolant or in-place raw water circuit cleaning.
    IMG_1816.jpg
    This is the other one (2" hose, about 65 GPM, 115V, 6 AMPS). It's got enough cord to go anywhere and enough hose to pump overboard from anywhere. I can always cut the hose and increase the flow if need be. Sure they both need AC power. But if I've lost the generator, I'm in my water wings waving bye-bye.

    So I say the crash pump idea on boats our size and operated by just one or two people sounds great if you're selling boating magazines. Otherwise...get a good Plan B.

    Naturally, the views expressed by the author are his alone and do not represent those of the station or its management.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  9. #9

    Re: How much raw water?

    All valid points. The gent that has the setup I referred to admits it's a last resort, and has several layers of protection above it. But at some point it can be better than nothing and it's not a lot of plumbing.

    My question however remains. How much water does the engine pump?
    1978 53' Motor Yacht "LADY KAY V"
    Hull number 524
    Chesapeake Bay
    https://ladykay.blog/lady-kay-v/

  10. #10

    Re: How much raw water?

    8v71 just over 60GPM,
    8v92 impellers are usually 1" longer. I would say just under 100GPM.

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