I have a Zenoah 260 with a BH Hanson 2 inch band pipe and a 100 degree header. There is a cooling flange attached to the header where it exits the motor and cooling at the meeting of the header and the pipe.

I have noticed that if I blow through the cooling line to the motor and cover the outlet, I have a nice tight feel with back pressure. This gives me a steady stream from that outlet when running.

But if I blow through the cooling line that runs through the flange of the header and around the pipe, I notice a good amount of leak when covering the outlet. This gives me more of a sputtering out of that outlet. I think this is the culprit to my boat taking on water during a run. I have tried replacing the O rings (7/8 Silicone) inside the pipe and adding a little grease, but still have a significant leak. I have also repositioned the pipe to make sure that nothing is causing a push left or right on the header causing the rings to squeeze to one side and allow a leak. I have a pipe stop that I drilled to keep the pipe from walking away from the engine and have a 1 in Viton ring at that fitting. The outlet from this flange is a large bore so I can't imagine that much back pressure causing a problem.

Can anyone suggest an answer to my leak or an alternative pipe and headere that would give me a better seal. The leak is clearly coming from the O rings within the pipe. I would like to make this equipment work and all the nipples are clean and clear.???

Yeah, the water-cooled coupler can be a real pain sometimes. I've had some that just never seemed to stop leaking until I changed headers. The aluminum headers can become distorted in shape really easy if heated up a bit too much and some point. The first thing to try is a good quality stainless steel header if you don't already have one on there. I would recommend the CC Racing headers as the quality is high and the tolerances are tight from one to another. I've seen headers from some other manufacturers vary so much that they definitely caused problems.

Other info:

Typically on the aluminum header setups, the silicone O'rings are better to use in the pipe coupler as they are softer and won't damage the aluminum header as much when it gets hot. Use Vitons in the flange (connecting header to engine).

If using a SS header, I use the Viton Orings in the pipe coupler and flange.

If the leak is happening with engine NOT running, try moving the pipe around on the header to see if you can stop it...this would indicate a bad or deformed header.

If the leak happens only when the engine is running, check the pipe mounting...that's your culprit.

You should normally check for leaks but creating a vacuum in the system (sucking rather than blowing into the lines). It should hold a good vacuum seal.

*last resort...if all else fails, weld the alum pipe to the alum header and forget about the water cooling.


If looking to get another pipe system altogether, of all the pipes I have tested, the most trouble free (and with least exhaust leakage) have been the CC steel pipe, CC Powermaster aluminum pipe, the Insane Dominator pipe, and the NeedforSpeed pipes (although there flange isn't the best...I prefer the no-leak flanges that the previously stated 3 pipes setups use). The QD Hotpipes are good pipes also, but they can be pretty messy until you get everything tuned properly. If you get a QD, I would strongly recommend the one from Redline Motors. There are a few pipes now being offered by Gizmomotors also, but I haven't tested any of those so can't really comment yet.

Thanks for the great info once again Marc. This place is such a valuable resource and helps to keep the trial and error process easy on the wallet.

I am so sorry to hear the loss of a fellow boater. Even though I didn't know him, it definitly gets to me when we lose a brother. There are so few of us accross the country. This hobby is closer to art than just another toy. Sorry to hear of another gone, especially with his contributions in design to the sport. A moment of silence in my thoughts, prayers, and heart.

Tropheus wrote:
Thank you very much. And it's always my pleasure to try and help fellow boaters.

Kind of reporting back after making an improvement. Note to anyone bulding a boat (fiberglass) right now. Put the engine in with the pipe installed and then line up the pipe bracket. I know it is common sense but I realized that my pipe bracket was putting just enough tension on the right side (pulling) of the Oring to cause a gap on the left. I realligned the bracket to remove the stress and bingo, the boat comes in dry and stays light.