Next year replacing my headers is going to be top of the list, so thank you for the photo.Can you 180 degree the photo?

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Hopefully this worked.. iPad photos are sometimes flaky when they upload...

Like I said, I REALLY hope I'm not thinking about this for a long time having three engines but if/when it happens, I would seriously consider these. The Hardin headers really looked solid. The outer tubes are larger than CMI's to have more water around the inner tubes. The guy at the booth told me that they also started coating the inside of the collector and that looked pretty good too. Wish there were more guys that had direct experience with these but I don't think they've been in existence that long. Definitely worth a look..

2004 twin 525s with 370 freshwater only hrs., run 60 psi water pressure at WOT, no leaks. I have a theory that the higher operating pressure, same principle that a pressure cooker operates under (raising the pressure raises the boiling point), helps keep the water at the header flange from boiling which improves the heat transfer capability of the surrounding water. Airated/boiling water carries less heat away at the flange weld. Call me crazy...

Is that 60 psi raw water pressure? The Mercury 525 service manual says that the max is 43 psi. I try to keep it between 35-40 wot. I've modified the inlet on my Imco shorty to help keep me within specs without running a pop-off valve. Wouldn't 60 psi be enough to risk blowing a heat exchanger? My headers stay cool to the touch and I check them often. They still have the flow restricters and I am not taking them out as long as everything is working fine.

Yup that's raw water pressure. I know everybody talks about 30 psi but after 10 yrs with zero issues I have no intentions of messing with the recipe

Yeah, people rip on me for letting it go over 40. I had put in a relief valve but 25 psi is not enough. Brownie (yup, Brownie) told me to lose the relief valve because it could stick open at a bad time. Good to know that the various heat exchangers can handle 60 psi!