Another 525 Header Issue
 

Looking for some direction. I noticed water dripping from the clamp that holds the tail pipe to the header on my 525. Pulled the header & pressure tested it at 60lbs & could find any water leaks. Is it possible the tail pipe could be leaking? I'm trying to figure out how I can pressure test that ( I have captains choice). Also when pulling the header I noticed that the restrictor fitting was missing in the top of the tail pipe. Any idea why someone would remove that? Thanks.

A leak at the clamp could be the gasket between the tail and the collector flange. As far as the restrictor fitting being missing, that was part of a Mercury service bulletin to improve water flow. Assuming that service bulletin was done, you should have a plug in the bypass fitting underneath the tail and you should also be missing the bypass hose that connects the distribution rail to that same fitting. IE: parts 15, 18 and 19 in the diagram should be missing..

Thanks. I'll try a new gasket this weekend. I have read a couple posts about the service bulletin. Not sure why mine has the lower bypass hoses still connected & top restrictors missing. Maybe the previouse owner was experiencing high water pressure. One of my water pressure gauges is fubard & the other I hope is reading high (reads about 35psi at 3-3500 rpms). New gauges on the way. What can cause high water pressure? My impellars & housings are new & the old impellars I took out looked fine. I have XR's also.

35 psi is right about where you want to be with the 525. The service manual puts the max at 43 psi. I know someone who runs 60 psi with no problems. Also, my headers run nice and cool as is so I did not do the mod. I have all the restrictors and hoses in place. What kind of lower drive do you have? Imco shortys send pressure sky high. I welded up a good portion of the inlet on mine.

My drives are just stock XR's. I'm just worried that if I run it harder the water pressure will get to high. Still getting used to the boat, only had it a little over a month.

Water pressure in the 30-35 range is good for the 525. You should sort out the problems with the gauges to be certain of where you're at first, but then you should remove the bypass hoses and plug the distribution rail and the tail port. The service bulletin was specifically to provide more cooling water to the jackets around the inner tubes of the headers. On the 525 headers, heat is the enemy. Perhaps the previous owner just wanted to restore the headers to original condition before selling the boat and just forgot to replace the restrictor fittings or lost them.

You might also want to replace the water pressure sensors while you're at it. I have Livorsi analog water pressure gauges (with the hose) but I had one water pressure sensor go bad and it made the gauge flake out. Once, I replaced the sensor, the gauge was fine. It's very easy on the 525, its right on top of the oil cooler.

I have mechanical water pressure gauges. I thought about just unhooking the line from the gages & buying a couple gauges from the hardware store & taking it for a spin to see if I get the same readings. I agree, once I have proven out the gages I will be removing the lower bypass.

Didn't notice this when I pulled the header. Split gasket.

There you go...