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Thread: Coolant circulating pump

  1. #1
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    Default Coolant circulating pump

    Iíve been using a 400w 115v block heater on my engine (Detroit 3-71) in winter. It not only helps immensely with cold weather starts, but it also adds a little heat to the boat to help drive out moisture. I love it when it works, but every two or three years it burns out and has to be replaced. The replacement process is a nightmare, the worst possible place to get an arm to hold a wrench that I have ever seen in all my years wrenching. So Iím looking at alternatives.

    I have a 15 gallon domestic water heater that is heated both by 115v shore power at the dock, and engine heat at sea. This means that while at the dock the engine coolant coil inside the water tank is sitting idle in 190 degree water. Seems like if I put a circulating pump on the engine coolant loop it would heat the engine.

    To do that, I wonder what type of pump one would use, and what would the monthly cost comparison be between the constant 400w block heater and the additional cost of heating the domestic water as it is cooled by the cold engine. And would this pump run continuously without wearing out. Anyone use a system like this?

  2. #2
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    Default Re: Coolant circulating pump

    Can you set it up to thermosiphon? That way no pump would be needed.

    IOW - the solar collector below is your heater & the tank is the engine:



    Most automotive style coolant pumps will be 12 volt: https://www.autohausaz.com/pn/039202...MaAq4BEALw_wcB
    "If it ain't broke, you're not trying." - Red Green

  3. #3
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    Default Re: Coolant circulating pump

    12v wouldn’t be a problem I suppose, the refrigerator is 12v and runs on the house bank being constantly charged by shore power. But I wonder about 24/7 constant duty of a pump. I also wonder why it doesn’t thermosiphon now but it may be that the engine’s 180 degree thermostat prevents it, which may also be a problem with the pump idea.

  4. #4
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    Default Re: Coolant circulating pump

    Following with interest as I have a nearly identical setup but without the block heater. Seems like something worth adding though.

  5. #5
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    Default Re: Coolant circulating pump

    You might consider a thermostatically controlled water pump from a household hot water heat system. I expect that they're very durable, and they're designed to pump hot water. Maybe someone here will have some ideas on how to incorporate the thermostat. I would just insulate the engine compartment and add a household thermostat. If the insulation were left in place all year it would help with sound proofing.

  6. #6
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    Default Re: Coolant circulating pump

    Quote Originally Posted by cstevens View Post
    Following with interest as I have a nearly identical setup but without the block heater. Seems like something worth adding though.
    Which boat? if you have a relatively easy access 3/4” unused plug on your engine block (most engines do, sometimes under a diamond shaped cover plate), I would highly recommended the 400w block heater. It’s only about $50 so if it burns out every two or three years, no big deal IF, IF you have easy access to change it. I’ll probably stay with it unless the pump idea works, but I went down to change it today and even with my notes from last time, I gave up after my aged body would no longer put up with the required contortions.

    1DE8D901-3A25-446A-88FA-BEEEFC7767B4.jpeg

  7. #7
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    Default Re: Coolant circulating pump

    A block heater (as Ron pictured) is by far the most efficient way to heat an engine. Generally they use 1/3 or less power than a tank type.
    "If it ain't broke, you're not trying." - Red Green

  8. #8
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    Default Re: Coolant circulating pump

    Well, both, but thinking of Skookum Maru specifically. Good thought on the block heater though. I’ll have to have a look this weekend when I’m back in Blaine. And in the meantime this:

    http://www.suremarineservice.com/Hea...ECUSTOMERPRICE

    might be useful?

  9. #9
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    Default Re: Coolant circulating pump

    Gotta make sure any circ pump can handle 200 deg. liquid.
    "If it ain't broke, you're not trying." - Red Green

  10. #10
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    Default Re: Coolant circulating pump

    Thanks for the link Chris. I always seem to forget about Sure Marine. Odd given that they are sure close . I’ll talk to them tomorrow.

  11. #11
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    Default

    Any pump designed for solar hot water systems will do I'd have thought.


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  12. #12
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    Default Re: Coolant circulating pump

    It sounds like one of these would do

    http://www.canadiantire.ca/en/pdp/ci...-0303295p.html

    It gets cut into a heater hose(3/4"-1") at a low spot so that it doesn't run dry.
    Little fuss to change it if it dies.
    In the winter, our loader (JCB 520-50) gets plugged into a receptacle thats downstream of a timer that comes on a 5am and goes off at 10am
    30 minutes at -20C, and it's is good to go.
    R
    Sleep with one eye open.

  13. #13
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    Default Re: Coolant circulating pump

    Quote Originally Posted by Ron Williamson View Post
    It sounds like one of these would do

    http://www.canadiantire.ca/en/pdp/ci...-0303295p.html

    It gets cut into a heater hose(3/4"-1") at a low spot so that it doesn't run dry.
    Little fuss to change it if it dies.
    In the winter, our loader (JCB 520-50) gets plugged into a receptacle thats downstream of a timer that comes on a 5am and goes off at 10am
    30 minutes at -20C, and it's is good to go.
    R
    That is interesting, except that I don't think it's a pump? According to the Phillips/Temro website:

    Most of these heaters heat and circulate the coolant by Thermal Siphoning. Thermal siphoning refers to the process of heated coolant rising, thereby drawing cooler coolant in to replace the warm coolant. The only Circulation Heater that has a pump is the Forced Flow Circulation Heater.
    Seems like that's pretty much just what the block heater is doing already? Although the external heater might be easier to change out in Ron's case.

    This is the forced flow pump:

    https://www.amazon.com/Zerostart-Tem.../dp/B01MFCHX8G

    Which does seem like a better option than the pumps from Sure Marine. Pricing is similar but it's a heater and a pump combined in one unit.

  14. #14
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    Default Re: Coolant circulating pump

    More like a coffeemaker than a plain thermosiphon.
    Mine is cut into the heater hose,and feeds toward the block.
    It comes out of the block and goes to the heater core in the cab,then back to the electric heater completing the loop.
    A total of about 12' of hose.
    An in-block frost plug heater only heats the engine block.
    R
    Sleep with one eye open.

  15. #15
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    Default Re: Coolant circulating pump

    Quote Originally Posted by Ron Williamson View Post
    More like a coffeemaker than a plain thermosiphon.
    Mine is cut into the heater hose,and feeds toward the block.
    It comes out of the block and goes to the heater core in the cab,then back to the electric heater completing the loop.
    A total of about 12' of hose.
    An in-block frost plug heater only heats the engine block.
    R
    "More like a coffeemaker..." - a perfect description! Makes sense then. Still I have to say I like that forced flow heater with pump. I have hydronic heating on Skookum Maru. I could add one of those heater pumps and keep the whole boat heated over the winter without having to run the diesel furnace. Might not keep things really warm but I imagine that it would be enough to help with freezing and dampness issues.

  16. #16
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    Default Re: Coolant circulating pump

    After trying and failing and getting really frustrated at trying to remove and replace my burned out engine block heater, and not being convinced of the circulating pump idea, I have been searching for other methods to winter heat my engine compartment. So I'm currently considering this 400 watt engine compartment heater (made for boats). A couple of questions; first, does anyone have any experience with one of these units? Is it correct to assume that 400 watts AC is the same draw on the shore power as the 400 watts of my old block heater? The block heater was on continuously 24/7 in the winter and never shut off, it had no thermostat control. Yet the elec. bill was not unacceptable. I assume this 400 watt electric heater would be no more expensive to run.

    https://www.fisheriessupply.com/cafr...ter-9510ca-bbx



  17. #17
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    Default Re: Coolant circulating pump

    This doesn't circulate the coolant directly but I have one on the oil pan on a timer and cover the engine (a small diesel) with a moving pad to keep the warmth in. The engine stays warm and starts right up (Maine winters in the water). I also have them on the batteries: https://wolverineheater.com/collections/watercraft
    If I had a dollar for every girl who found me unattractive, eventually they would find me attractive.

  18. #18
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    Default Re: Coolant circulating pump

    Nice! Those look really handy. It's now a Phillips & Temro product though, with a new website:

    https://phillipsandtemro.com/solutio...y/pad-heaters/

  19. #19
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    Default Re: Coolant circulating pump

    So do you just drape this flexible heating pad on the engine? Not sure how you would put it on the oil pan
    Elect a clown expect a circus

  20. #20
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    Default Re: Coolant circulating pump

    Quote Originally Posted by Bobcat View Post
    So do you just drape this flexible heating pad on the engine? Not sure how you would put it on the oil pan
    3 or 4 sheetrock screws though the heating pad & into the oil pan should do it.

    More seriously - I believe they are glue-on.
    "If it ain't broke, you're not trying." - Red Green

  21. #21
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    Default Re: Coolant circulating pump

    I’ve heard from more than one source that the heating pads glued to the oil pan can be problematic. The glue eventually fails and if you have any oil or coolant seepage at all the pad can become a mess that is half falling into the bilge. This is all heresay, and may be due more to careless users than the product itself.

  22. #22
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    Default Re: Coolant circulating pump

    "Eventually" can be a long time. I've had a heating pad glued to the oil pan of my aircraft's engine for 20+ years and it continues to perform well. Like a boat, that's an environment that sees lots of leaky oil, lots of vibration, and plenty of water when I fly through rain. An aircraft engine is a lot easier to work on than a boat engine when you take off the lower cowling though. Not sure I'd want to get under the oil pan in my bilge to clean it and attach a heating pad. I can reach under there so I suppose it could be done... We live in a clime where the coolant intake would freeze anyway, so I haven't messed with engine heaters on the boat.

  23. #23
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    Default Re: Coolant circulating pump

    so, have you guys looked at the auxiliary portable block heaters available at truck stops?
    there are two in particular that i see potentially useful in your situation, amazon has a number of them for sale:
    1. there are oil pan heaters which stick to your block magnetically, they range from 200 to 400 watts and run on 110
    2. oil dipstick heaters, simple, just replace your dipstick with a heated one, they do require that you can submerge the end of the dipstick in usually about of four inches or so of oil, they're usually about 100 watts

    a third easy option, if you sort out your thermostat, would be to install a lower coolant hose heater

    Simpler is better, except when complicated looks really cool.

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