Dual Cooling How-To!

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  1. #1
    Resident Guru XXX Racing's Avatar
    Join Date
    Jan 2003

    Dual Cooling How-To!

    It is the riding time of year again! As so many people are out riding their skis, they're paying attention to how they'd like to enhance performance in one way or another. Performance is a great thing - it brings out the potential hidden in your ski, demands more of it's rider, enhancing his skills, and personalizes your craft - but it also enhances another aspect of the engine that many will forget: heat.

    Getting rid of engine heat is typically overlooked in favor of more exotic modifications like an expensive pipe, aftermarket cylinder heads, or a sweet lookin' billet carb setup. There is no glamor for the work involved, and certainly no "trick" factor. However, it has become apparent to me that many riders on this message board are paying attention and would like some information and help regarding this type of modification. It is to this crowd that this post is aimed.

    I will expect, for the purpose of this post, that anyone performing this alteration to their craft will have a good selection of tools, or the availability to obtain them. In most cases, it is not cost-effective to own many of the tools I will list, however, I've never experienced any remorse for owning any tool. It also comes in handy should a friend of yours want to perform the same modification or if you should need to perform it again yourself - like in my case of owning too many skis!!

    Besides the regular tools needed for assembly and disassembly, you'll need the following to complete the modification:
    Screwdriver or 1/4" driver for hoseclamps
    1/8" NPT tap
    5/16" drill bit
    3/8" high-speed drill bit, 3 feet long (more later)
    Epoxy or Marine Tex
    Red Loctite
    1/2" auger or drill bit
    Tubing cutter

    4 feet of 3/8" OD aluminum or copper tubing
    (2) 1/8" NPT x 3/8" hose barb brass fittings, 90 degree
    (1) 1/8" NPT x 3/8" hose barb brass fitting, straight
    (1) Bypass Fitting
    Extra length of 3/8" ID hose - approx 3 feet (I recommend automotive fuel line) *OR* 6 feet of NEW 3/8" hose to complete the system
    (6) All stainless hose clamps

    I am assuming you know how to dissassemble your jetski. It is my purpose to make this article applicable to most watercraft makes out there, to include dissassembly information would make it 8 pages long! In the interest of keeping things short and to the point, that information will be left out. I recommend that anyone wishing to work on their watercraft have the maintenance and repair manual(s) handy - Clymer makes the best out there.

    I am aware of many cooling system configurations and routings. This article will only instruct dual cooling lines feeding the engine. If you desire a different design (like in the case of the exhaust being fed separately from the engine), so be it - I will not be discussing these routings, but my information is still useful and applicable to these designs. Simply modify them for your own needs.

    Starting Point:
    The pump will be out and disconnected from your ski, and it sometimes helps to have the impeller out as well. The exhaust manifold will also need to be removed - follow your manual's recommendations on what else will need to be removed prior to get to that point. To make this modification really worth your while, remove the cylinder head as well.

    Drilling and tapping of the head can be done while it is still torqued to the cylinder - however, a small mistake can ruin a very expensive engine, therefore the risks FAR outweigh the extra 10 minutes to simply remove the head, in my opinion. NOT WORTH SAVING TIME!

    1 - Pump Removed
    1a - Impeller Removed
    2 - Exhaust Manifold Removed
    3 - Cylinder Head Removed

    Prepping the components:
    You will need to drill and tap the pump for a second waterline fitting.

    Under examination, you should find that the original fitting is located on the bottom of the pump, approximately 4 or 5 o'clock as you look from the rear. You will want the second fitting to be located about 7 or 8 o'clock - or 90 degrees from the original fitting. The distance front-to-rear of the pump is critical - the manufacturers have seen fit to place the original fitting just at the beginning of the stator section (in most cases), I recommend that you locate your new fitting identically. (See pic below) Many Yamahas or skis with aftermarket pumps have raised bosses on the pump housing specifically for additional cooling lines - inspect your pump to see if you already have such provisions.

    440 pump with dual lines

    Dril the pump with a 5/16" bit in the correct location, and tap with the 1/8" NPT tap - periodically screw in the brass fitting to make sure it goes to a depth great enough to seal well. Do not be worried if some of the fitting protrudes into the pump body unless it impedes the impeller's movement. I always grind mine down with a Dremel tool or file anyway.

    The aim of the nipple on the fitting is pretty important, so you may want to hold the pump body in place a few times and adjust the direction of the brass fitting for optimum clearance with a hose installed (you can save this until last so you can be totally sure). I use red loctite or JB Weld (epoxy) to hold the fitting in place. (Note: Some pumps do not have the "space" for a 90 degree fitting to be threaded in sufficiently. In this case, I have used a 90 "street" elbow with a straight nipple to achieve the desired results. Inspect the 550 pump on the left in the above picture for an example.)

    The exhaust manifold is where the ski is designed to take in the cooling water. Examining the cooling jackets will give you a good idea where you can locate a new fitting without piercing the ports. Kawasaki 650's and 750's are particularly tricky, but it can be done. I prefer,if at all possible, to place the new fitting opposite the first fitting. For example, Kawasaki 440's and 550's take the cold water at the rear cylinder, if you were to place another fitting at the front cylinder, the ports would be equal (as far as cooling is concerned). This being said, the stock 550 manifold can only take a second fitting on the rear face, and a stock 440 manifold has a raised boss that makes it ideal for another fitting. Do the best you can. Most aftermarket exhaust manifolds are already designed for dual cooling. Drill and tap the exhaust manifold and install the straight 3/8" fitting using the same methods described for the pump.

    Aftermarket 440/550 manifold with dual inlets

    The cylinder head will also need to be drilled and tapped for an extra waterline fitting. This will not be plumbed into your cooling system, rather it will simply "bypass" all of it and purge water overboard. Newer Kawasaki heads often have a flush fitting or plug already in the cylinder head - I would use this and be done (head does not need to be removed). Older Kawasakis (300, 400, 440, 550) were manufactured with the thought of a bypass in mind, but without the modification completed. 440's have two threaded plugs on top of the head, but they often need to be drilled oversize or re-threaded, 550's have the plugs machined flat and they will need to be drilled out. I prefer to use the rearmost plug on these heads as it equalizes cooling water output between the front and rear cylinders, and the material of the head is very thick and sturdy in these locations. I have used the very rear of the cylinder head before (just like the front) with no problems - if you want to experiment, you can. The reason to bypass water from the cylinder head is twofold, or all that work you will go through getting the water to the engine will do nothing. One, twice the hydraulic input requires twice the output, otherwise the result is zero - each line would only flow to half its capacity because the output is only half the input. Two, running all that water through your exhaust would certainly be restrictive to power output, rendering this a modification that LOSES performance. No bueno.

    750sx with two outlets

    Two ways of adding a bypass on the JS440/550 head

    1 - Pump able to deliver more water
    2 - Exhaust manifold able to accept more water
    3 - Cylinder head able to bypass the excess water

    Getting the water from A to B:
    Now that the easy stuff is over, it's time to get down to the nitty-gritty of this project. This part is not for the timid - it is very easy to misjudge your aim and put a decent hole in your hull where you don't want a hole to be.

    The tool: Many kits for dual waterline conversions are very easy to piece together, save for the drill bit - this is obviously why the kit is in existence. I once borrowed a drill bit from one such kit, and copied it that very same day so I could have my own. It is a 3/8" high-speed bit welded to 3 feet of 3/8" steel rod. It would be impossible to complete this modification without this tool, I know, I've tried. If you cannot weld this tool together yourself, I am sure that a competent shop would be willing to do it for you in a matter of minutes. Grind all welds smooth to the shaft of the rod - it is important that it be able to pass through all the foam and fiberglass in your hull without hanging up.

    Pick a spot and go!

    Just Kidding! Actually, you should spend plenty of time inspecting, verifying, ensuring, contemplating, and inspecting again to be doubly sure where you want the line to go, and that it can actually go there. I've included pics of a dual-cooling line from one of my 550's to show you the best location for my application. You can see that, from the rear, there is ample space in the pump cavity below the steering cable for the line. In the engine compartment, there is even a hole in the bulkhead - though I challenge anyone to actually hit that accurately; I never have! When you drill, you will pretty much maintain parallel with the hull, and a tiny bit inward. Going up would certainly pierce either the original cooling line (which crosses from right to left in the area you will be drililng) or the steering cable tube or the cable itself.

    Most guys just gloss over this part like pushing the line through the hull is no big deal. Remember, aluminum and copper bend! Sometimes pushing this line through the hull is like trying to shove yarn through there! Be careful and take your time - it'll go. If you purchased the 4 feet I recommended, you should have about 6 to 8 inches on both sides (will vary depending on craft, most standups can use 4 feet - measure first if unsure). Use the Marine Tex or JB Weld to hold the line in place. Do not lose patience if it takes two or three applications to get a good bead around the tube strong enough to keep it from moving. I also NEVER trust that stuff to make a perfect seal, so I will run a blob of silicone around the epoxy to keep 'er watertight too. By the way - do this on both the engine compartment AND pump cavity sides of the hard line. Use the tubing cutter to trim the lines down to leave about 3 or 4 inches sticking out.

    1 - Hull drilled
    2 - Line installed, sealed, and trimmed

    Buttoning it back up:
    Reinstall all the removed parts using new gaskets, sealers, and whatnot described in your manual. In the pump cavity, you will need to reconnect the original cooling and bilge line, and tighten all hose clamps. Connect the new fitting you installed with the hard line you also installed using a new length of hose and two clamps. Be careful pushing hose on the second line, as you may compromise the strength of the epoxy job you just did - to be sure, lube the hose with soapy water. Finish by installing the ride plate and intake grate.

    The exhaust manifold will get a new length of hose and two hose clamps too - be careful not to manhandle the new cooling line too much.

    I forgot to mention much about the location of the bypass fitting - that was on purpose, as I usually save it until now since I regard it to be cosmetic. On my 550's, I prefer to have the bypasses on the port side of the craft, with the lines quite far back in the engine compartment and behind the exhaust pipe. You will need to select a location that looks appealing from the outside and has plenty of room on the inside for you to get your hands around (tightening clamps is a ***** when it's crowded!) - keep in mind simple maintenance items like removing the battery, bilge pumps, cleaning, etc; you wouldn't want to have a bypass line always in your way frustrating you as you work around it. Drill through the hull first with a small drill bit to align the larger 1/2" bit or wood auger, and bore through. Install the bypass fitting with silicone to the hull *and* on its threads, and tighten well.

    As with the pump, it's nice to have the brass fitting on the cylinder head "aimed" towards your bypass fitting - this allows a shorter length of hose, a less-crowded engine compartment, and doesn't look so ameteur.

    1 - Pump reinstalled and hooked up to dual lines
    2 - Engine reassembled and hooked up
    3 - Cylinder head torqued with bypass installed and hooked up

    That's it! I would give the epoxy at LEAST 24 hours to completely cure before submerging it in water. When you get it on the water for the first time, give a double, triple, and quadruple check for leaks around all your hose clamps and hard line. When everything is working correctly, you will have a great stream of water from the bypass fitting - this is a perfect indicator of the cooling of your craft. If you notice any changes in that bypass stream, check out your system.

    1/2" Cooling
    I have become a recent convert to 1/2" cooling lines in place of dual 3/8" lines. In my opinion, when I'm neck-deep into modifying a ski, I may as well go all the way and do the 1/2" line. A second 3/8" line takes a little less work since the first 3/8" line is already in there for you - going to a single 1/2" line requires a couple different changes, but then again I'm usually up to my ears modifying a ski so everything is often apart for me anyway. The process is quite the same as adding a 3/8" line, just a bigger scale.

    First, it would be remiss of me not to discuss why or why not.
    Why? A 1/2" line is larger, and thus can hold and deliver a larger volume of water than a single 3/8" line. Being as its diameter is 33% larger and the area is 56% larger, it can deliver 78% more water volume. To clog a large 1/2" line would take a mighty clog, which makes this a problem of the past. It happens rarely.
    Why not? Even though it's larger, it's still only one line without a backup. If something should happen to that one cooling line, you're overheating. Two 3/8" lines has a surface area of .220 inches compared to a single 1/2" with .196 - the difference is slight, but it's still more water. Plus, you have a backup if one gets clogged.

    Take into account, by the way, that most dual 3/8" lined skis don't actually have two 3/8" lines - the stock Kawasaki line in a 440 is actually 1/4"!! A 750 uses a 7mm line hooked up to 1/2" lines on 3/8" fittings. Go figure. So going to a single 1/2" is often more water than a ski using the stock line and an additional 3/8" line.

    Brief How-to:
    I try to rip out the original hard cooling line if at all possible. If this can't be done (it's been 50/50 in my experience), I cut the ends flush and drill through it with a 3 foot 1/2" bit. I like to put the 1/2" line in the same hole in the pump cavity as the original 3/8" line - but it'll come out in the engine compartment on the right side and not the left side - no biggie, but it'll just take more hose to cross over. I use 1/2" heater hose. I am sure to seal the end of the old 3/8" line with silicone to avoid the foam getting water saturation.

    The pump fitting gets removed, and the pump gets redrilled and retapped for a huge 1/4" NPT x 1/2" hose barb fitting. Same for the exhaust manifold - though on 440's, I don't trust the original location and will instead prefer the boss cast into the side of the manifold. When using different locations for fittings and NOT modifying the material for a larger one, you must plug up the old hole with a brass pipe plug. Typically, the only one will be on the exhaust manifold.

    The rest of the engine is hooked up with 3/8" lines. That's still plenty of water for the exhaust system as well as a bypass fitting. Since the flow rates (of a single 1/2" versus two 3/8") are close to equal, it'll all work perfectly.

    There you go!
    I tried to explain dual-cooling and how to do it as quickly and non-technically as possible. Most skis can operate very well on their stock cooling lines, but any modification that deals with reliability is a must-do in my book. I will never try to talk anyone out of performing this modification, unless they don't seem to have the understanding and patience to do it. You will have to judge for yourself if you think you have the patience for doing this. I rate this as a "6" on a 1-10 scale of difficulty.

    Stand Up Rider #37

  2. #2
    Wow! Good report. Some of us needed this! Thanks!

    I also liked the one on the waterboxes!

  3. #3
    I dream skis 550$$$'s Avatar
    Join Date
    Jun 2004
    San Marcos, CA
    XXX- I like it, I like it allllot! What about an article on waterboxes?
    1988 JS550

  4. #4

  5. #5
    I dream skis 550$$$'s Avatar
    Join Date
    Jun 2004
    San Marcos, CA
    Thanks Xlrator. Too bad I already bought an aluminum waterbox a few years ago. Would have saved me a LOT of money!
    1988 JS550

  6. #6
    XXX, I followed your instructions when I installed dual cooling on my 550 last year!!! the instructions were great man...

    It was so much simpler to do on my 650SXs though. I like that pipe drain installed by kawi. It makes a great cooling line once you get rid of the stock pipe.

    I'm glad to see information like this shared so freely.. The internet is such a wonderful thing!

  7. #7
    What about when running on a flush kit? I have mine on the original line between pump and manifold. What about the second line?

    I'm trying to think this out, but my head isn't clear.

  8. #8
    Join Date
    Feb 2004
    not at X-EGO
    you dont do anything different while flushing if you have dual cooling.

  9. #9
    XXX, excellent post - keep em comin!

    I was on the fence with dual water on my 2nd x2....gotta do it now!


  10. #10

    Very nice


    That was very generous of you to take the time to put this guide together.


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