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Thread: Hydro - water outlet on the bottom?

  1. #1
    Join Date
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    Default Hydro - water outlet on the bottom?

    Hi,

    I was wondering - as a first time builder - if there are any problems simply putting the cooling water outlet on the bottom of the hull as opposed to the transom or side. The two problems I can see is water pressure on the outlet working against the rudder pickup and outflow interfering with the prop. As for pressure, neither of the marked surfaces B and C should touch the water at high speeds, so we are talking only about hopefully negligible air pressure. To avoid interference, if that's at all a problem, I can move the outlet sideways, out of the line of the prop.

    Could someone more experienced chip in with some useful info? Is this a bad idea? Pros and cons?

    The reason for this whole fuss is that the transom is too thick, so I would need to remove the inner balsa layer from the outer plywood layer. On top of that, the transom is already pretty crowded, so accessibility for servicing is also a concern.

    IMG_20200130_214049.jpg

    Cheers,
    Peter

  2. #2
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    GB
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    Default

    It is fine there if that is where you want it. Back in the brushed NiCd days I used to exit downwards next to my motor, to minimise weight and for a tiny bit of extra lift any half decent water pickup will have no trouble pushing past the raised air pressure in a tunnel. These days I like to exit on the left side so I can see the flow most easily as the boat goes past on the pit straights.

    I find a transom outlet hard to see as there is water coming off the prop and rudder there, but if you want it there it is no problem, chuck that fitting in the spares box and glue in a short length of alloy tube, or for ultimate neatness and lightness glue a long length in through the transom and all the bulkheads straight to the motor with just a short silicon connector to the jacket.
    Paul "tug Killer" Upton-Taylor, Cat lover.
    FastElectricBoats.co.uk

  3. #3
    Join Date
    Aug 2015
    Location
    MI
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    Default

    Only think I can think of at the moment is: as you run the boat near by you can see if there is water going thru the system (most that I have seen outlet is on/near the port side since races are counterclockwise) Could come out near transom thru decking (or anywhere else of the decking near the gunnel) so that you can see to make sure there is water flowing through.

    Biggest thing is making sure there is water flow, if its through the bottom of the hull ???? is there water flow?

    One time my motley crue came by, seen no water discharge, docked it and motor/esc were a bit hot, but not excessive, lucky me. Stock pick up was plugged with seaweed. I think if I continued with it plugged I would have fried motor and or esc.

    But it's your call, just giving my $.02 worth

  4. #4
    Join Date
    Oct 2015
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    Ca
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    Default

    Put it where you can see it,even straight up through the deck.It is VERY important to verify the cooling is working. Otherwise it will get expensive real quick. By the transom is not good, too much spray to know if it's the cooling or just the prop.

  5. #5
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    Default

    Thanks for your answers everyone. I think I'm gonna drill it through the side next to the motor with an alloy pipe so that the flow can be seen.

    As for the ESC and the motor, do you suggest I hook them up to the cooling flow in parallel or in serial? If serial, I'd put the motor first so that the ESC gets the warmer water -- it has an overheating failsafe.

  6. #6
    Join Date
    Sep 2012
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    Default

    Quote Originally Posted by petiaccja View Post
    Thanks for your answers everyone. I think I'm gonna drill it through the side next to the motor with an alloy pipe so that the flow can be seen.

    As for the ESC and the motor, do you suggest I hook them up to the cooling flow in parallel or in serial? If serial, I'd put the motor first so that the ESC gets the warmer water -- it has an overheating failsafe.
    Water cooling should go to the esc first then the motor. Make sure that the cooling line to the motor goes to the low side of the water jacket and out the high side for best cooling. Do it in 'series', don't use y fittings and split the flow.
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
    2016 SUHA Q Sport Hydro Hi Points Champion.
    BOPMPBC Open Mono, Open Electric Champion.

  7. #7
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    Default

    Water cooling should go to the esc first then the motor. Make sure that the cooling line to the motor goes to the low side of the water jacket and out the high side for best cooling. Do it in 'series', don't use y fittings and split the flow.
    Great, thank you! Would you mind explaining the reasons? I'm just curious.

  8. #8
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    The esc being electronic needs the cooling first. Electronic stuff does not like heat. Fortunately most esc's have thermal cut outs to save them from burning up. The motor can handle a little more heat. However you should be trying to keep the lot as cool as possible.
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
    2016 SUHA Q Sport Hydro Hi Points Champion.
    BOPMPBC Open Mono, Open Electric Champion.

  9. #9
    Join Date
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    Cool

    - Water cooling should go to the esc first then the motor. Cooler water reduces heat faster.

    - Make sure that the cooling line to the motor goes to the low side of the water jacket and out the high side for best cooling. This routing insures that the water jacket is full and doesn?t have a large air bubble trapped at the top.

    - Do it in 'series', don't use y fittings and split the flow. When using a ?Y? fitting the water will take the route of least resistance, meaning the flow will not be equal through both lines.



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