Water cooling a briggs?

Discussion in 'DIY Marinizing' started by Rangerspeedboat, Apr 18, 2009.

  1. Rangerspeedboat
    Joined: Apr 2009
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    Rangerspeedboat Senior Member

    I have had this idea for quite some time now and need feedback.

    I would like to convert a air cooled 10hp briggs and stratton to water cooled. The main part being cooled normally is the cylinder and head due to all the fins to get rid of heat. Here are some ways I have thought about

    1. Wrap 1/4" copper pipe in between the fins on the cylinder and head, have a rubber hose to connect the copper pipe on the cylinder to the copper pipe on the head. I would do this so I could take the head off one day without taking off the pipe. Pump water though the copper pipe for cooling. This method is easy but might not yield enough cooling.

    2. Make a watertight box to fit over the cylinder and head while leaving a space for the sparkplug, intake, and exhaust. This water box would be filled with water and provide excelent cooling but is hard to make right and salt water would eat up the aluminum.

    Those were the only two feasable ideas I could think of.

    I would have to take the temperature of the engine with a non contact laser thermometer with the engine having no modifications to it first. Then modify it and see what the difference is. I would monitor it constantly so I would not burn up the engine.

    Please share your thoughts on the subject.

    Why do I want to do this? For fun and to eleminate the need for the engine to get alot of air in tight spaces for proper cooling.

    Thanks, Ranger
  2. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    I did it once. I put a rag on engine, pour a little water on it every time it got dry. Ran good. The point is, for water cooling, you need a pump and water. After that cooling is easy since you have unlimited water supply.

    Actually did this to get home, coil was malfunctioning because it was getting to hot and shutdown engine.
  3. Rangerspeedboat
    Joined: Apr 2009
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    Rangerspeedboat Senior Member

    This engine will be used in a boat and connected to a 9.9 mercury lower unit. The lower unit will provide plenty of water for the engine, for testing it out I will just connect a water hose to it.

    After putting the rag on the engine, did you see any corrision or other effects?

    Thanks, Ranger
  4. alan white
    Joined: Mar 2007
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    alan white Senior Member

    You may as well forget about cooling the Briggs with water. Any casing would have to be welded on and I'd guess it would be nearly impossible to do that without distorting something. Then, you have a block that isn't as strong as before because aluminum welds are not nearly as strong as the casting or base parts, not only because of metelurgy, but also because of inconsistancies in smoothness, which causes structural weakness. You can't grind what you can't access.
    If a cyliinder head is removable it's conceivable that it can be replaced by a new water-jacketed one (though the head is still air-finned). This would be fine if Briggs made such a part, but unless they do, making one would cost enough to nix the idea quickly.
  5. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Hi Ranger,

    Looking at your reasons for trying this:

    (1) For fun - I take it you're one of those folks who likes to tinker with the machinery :)

    (2) So you don't need lots of airflow in a tight engine bay - On a gas powered boat, you need airflow into the engine bay for combustion, and you need substantial flow through and out of the engine bay to clear out gasoline vapours. Engine bay ventilation is a legal requirement, and on a small boat is not usually that difficult to achieve. Would it be feasible, in your case, to use a continuous-duty engine room exhaust blower in a larger size than you'd normally fit to a boat like this? With careful planning of the air flow patterns, it should be possible to get an environment in there that the little Briggs will be happy with.
  6. Rangerspeedboat
    Joined: Apr 2009
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    Rangerspeedboat Senior Member

    Why would a casing have to be welded on? I have some aluminum diamond plate which I could clamp over the cylinder and sealing it with some high temp sealant. Sure over time due to vibrations and what not it would start to leak but it might work.

    I went shopping with my parents today and while we were out I got 20' of copper tube, 8" of rubber hose and a laser thermometer.

    Another reason I would like to do this is that the mercury lower unit already has a water pump built in, so why not use it :)

    I'm still going to try, but will proceed with caution. The last thing I want to do is blow my motor.
  7. Rangerspeedboat
    Joined: Apr 2009
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    Rangerspeedboat Senior Member

    Here are the base line temperatures. I ran the engine for 10 minutes measuring the temp every 2 minutes at 3 different spots.

    Starting temperature 78.1 @sparkplug, 78.4 @crankcase, 79.4 @shroud

    Minutes running: Sparkplug : Crankcase : Shroud :
    2 168.4 84.4 82.1
    4 204 96.1 84.4
    6 220 109.1 87.8
    8 234 120.8 88.6
    10 233 128 88.3
    Temp Increase 155.9 49.6 8.9

    All the measurments were taken from the same distance and in the same order to insure consistancy.

    Now that that is done I will wait for it to cool and then wrap it in copper pipe. If I have a significant increase in temperature within too short of time I will stop the test.

    Edit: Sorry, when I typed it it was all spaced out like it should be
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If you use a "non-touching" thermometer you where not getting a good reading. If you where using a direct contact type, then something else was wrong, because the head gets a hell of a lot hotter then that.

    The surface area on copper pipe will not be much, certainly not enough to make a substantial difference in the cylinder temperatures.

    No "high temperature sealant" that I'm aware of, will tolerate the temperatures found near the exhaust port. It's possible you might get a few other places to stay stuck though.

    Your problem is air flow, not enough of it in this case. If your engine is the type I suspect, it pulls air in through the top where the pull rope is located (or where it would be on a pull start version). This is typically on the side of the crankcase opposite the output shaft. Air then flows around the cylinder and exits by the exhaust and intake ports. This is the general way most of these "lawn equipment" engines are cooled.

    You can easily improve these. The first thing to do is separate the intake air, from the exhausted cooling air. Some simple sheet metal work can solve this. What this does is provide cool, clean, fresh intake air, instead of recycling a portion of the hot exhausted cooling air. You can take this further if desired, which will improve fuel efficiency and offer a slight HP increase, by providing a separate cool air intake for the carb. You can do this with a piece of PVC pipe on the carb, which raises up the air cleaner out of the engine's heat, into cooler air, or duct cooler air to the carb inlet.

    Another trick is to install a fan. Remove the "grill" from the fan end of the shroud and install an electric fan. You should have enough electricity generated from the stator to easy drive a fan to push enough volume across the cylinders. Build a new shroud around the fan so you don't have leaks to the old shroud.

    If I remember, we've had this discussion before, where I suggested you'd have a cooling issue. In fact, I'm still curious about a clutch on your setup.

    The bottom line is you need enough air through the engine and no big "heat sinks" near by to suck up heat and radiate it back to the engine (read no enclosure without lots of big holes).

    The crank fan will do the job if it can grab enough cool air. Put it in a box and it can't grab enough and has to live on engine heated air.

    Duct the air into the crank fan, then out in it's own duct, with little or no leakage and you'll be fine. Enclose it and it'll eventually heat up the air inside until it cooks itself.

  9. Rangerspeedboat
    Joined: Apr 2009
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    Rangerspeedboat Senior Member

    I was using a non-contant laser thermometer, and I knew that it was off; but it would give me consistant readings as " it may be off, but its consistantly off ;) "

    I deciede to give up on the project, there is no way that I could wrap the copper inbetween the fins. I would have to take the engine off and do alot to it. I just figured since I have a water pump why not use it? I will probably have some other use for it. Possibly shooting water into the exhaust pipe to keep it cool and to have a giant steam cloud :D

    There will be a cover over the engine but it will have alot of vents, or I might just get a window screen or something similar to not have the engine showing.

    Now I have 20' of copper tubing, probably use it for fuel line and clamping cables together.

    I like the sheet metal ducting idea and the PVC pipe for the carb. I will use these, but I have to make the boat first.

    I like to experiment with things and get feedback about them.

    I have another question about vacuum fuel pumps but will start a new thread.

    Thanks for the help, discourgment, encourgement,and listening. (really no joke)

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