XPL Coffman - Dual Cooling Setup - Power Loss

[seadooaddiction]

So I added a dual cooling setup to my XPL Coffman build since I didn't like how hot the pipe was running. After I installed the dual cooling the machine just feels much lazier and is no where near as responsive. The ski lost 100 revs on top and seems to have developed a miss when I hold WOT and load the pump with a left hand sweeping turn.

Im thinking the coffman is designed to run hot. Its never sizzled water after a moto but will burn ya if u touch it for too long when running the standard setup spec'd by coffman.

Anyway. Why would adding more water to the water jacket effect engine performance? The same amount of water is being introduced into thr expansion chamber and jetting did not change. I did just fuel up before test with 93 octane so perhaps bad fuel?

Any thoughts appreciated. Thanks

 

[1of500]

I don't know the technical terms but doesn't cooling the pipe change the exhaust wave. Changing the power band and revs . I think that's what water injection does on fpp I've read so much on the different aftermarket exhaust systems it's all running together atm

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[seadooaddiction]

Im not changing the water in the exhaust chamber itself. so its not directly changing the exhaust wave but perhaps indirectly with increased cooling...?

 

[1of500]

Yes. Isn't there a Coffman instructions sheet on pwc2day?

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[seadooaddiction]

I had it setup as per the coffman diagram but i didn't like how how it was to the touch. Everyone I've asked who ran n one said they were always able to touch the pipe or it at least be cool enough to where it won't burn you.

 

[seadooaddiction]

 

[1of500]

Does it burn if you hold your hand on it or just touch it? Have you tried increasing the 135 jet?

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[seadooaddiction]

I may revert back to standard cooling and get an actual heat reading on the pipe. I don't have egt's or a temp sensor display so i just orders a thermal laser pointer to get a real number as far as temperature.

 

[1of500]

I guess this is our problem with 2 stroke go fast parts there is no one you can just call and ask

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[seadooaddiction]

Does it burn if you hold your hand on it or just touch it? Have you tried increasing the 135 jet?

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It burns when u leave ur hand. Touching and and take away is ok. Havent seen it steam water if I splash it at all either. The 135 jet doesn't affect water jacket temperature, or at least as I understand it shouldnt affect it much at all.

 

[1of500]

Braley may know have you texted him

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[seadooaddiction]

My 951 gurus are MIA at the moment. I've been tasking Braley already with my x4 951 pump conversion issues...

 

[1of500]

I've got a really tall prop for a 140mm 17.5x26.5

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[1of500]

Was on a xp800 I parted over winter

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[Matt Braley]

I guess this is our problem with 2 stroke go fast parts there is no one you can just call and ask

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I take offense to that I'm working during all waking hours over here, lol.

 

[1of500]

Lmao I was referring to the manufacturer

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[seadooaddiction]

still searching for the cause of this... did a compression test today and the front cylinder read 145 psi and the rear 150 psi.

Im starting to think that there was potentially a pin point hole in the water jacket to the expansion chamber. Now that i am running that much more water through the water jacket, potentially significantly more water may be getting introduced into the expansion chamber through that hole. A leak in the water jacket may have been exasperated and is now causing my power loss. Im thinking i need to get setup to pressure test the pipe.

 

[1of500]

Rubber plugs and a pop off tester


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[Matt Braley]

Yes or even a piece of hose and a couple thumbs. When you blow in it it should hold and blow right back at you. If air is escaping you can feel/hear it. The water injection fitting goes all the way through so it's separate from the water jacket.

 

[seadooaddiction]

Does that sounds like a good possible source for this power loss?

 

[seadooaddiction]

Yes or even a piece of hose and a couple thumbs. When you blow in it it should hold and blow right back at you. If air is escaping you can feel/hear it. The water injection fitting goes all the way through so it's separate from the water jacket.

Can this be done while pipe is installed?

 

[seadooaddiction]

Well I just hooked up a hose to the stinger side water jacket and put my thumb over the top stinger and blew... Sure enough I hear a slow constant hiss. Put soapy water around fittings and clamps and didn't see any active bubbles... not liking where this is going...

 

[seadooaddiction]

Forgot about this thread while I was working on my x4 but turned out to be a pinhole in the inside water jacket. Was able to locate general area and took the pipe to a local welder I found. A few days later the pipe was fixed and ready for the water. Dual cooling is now running beautifully on the boat. Last day on the water the motor rev'd over 7600 rpms and the boat gps'd @ 66 mph. Need to bring those rpms down a cpl hundred and should pick up another mile an hr or so on the top with a bigger prop. I've also installed a 1/4" jetworks flow control valve and a 150 hard jet onto the waterbox. I was having some issues with the waterbox and exhaust couplers overheating due to a clogged stinger jet that I didn't find until after i had the flow control valve installed. So i closed it up a little after I unplugged the stinger and figured as long as im not losing performance, a little extra water into the water box won't hurt. The stock regulator provides water to the waterbox but the suggested coffman setup had that fitting blocked off. In any event, the extra cooling hasn't hurt performance, so its staying for now.

 

[Matt Braley]

Thanks for the update. I'm glad to hear it's fixed and running well.

 

[seadooaddiction]

New update on XPL coffman boat:

Sourced a 16/23 148mm impellar to replace my 16/21 prop that turned 7600+ rpm.

New rpms maxed out @ 7500 and top speed now 67 mph without any noticeable loss in acceleration,

I am thinking i may be able to squeak another mile an hr with a slight tweak of the prop to bring it down to 7400 rpm. I'd love to see 68 out of my humpty dumpty xpl.