Both of my 525 Mercury Racing Engines showed milky oil above the full mark. Pulled both motors, took them to Don @ Motor Machine Shop in Sacramento. Don pressure checked all four Headers before tearing down the motors, all four were cracked. I called CMI & Mercury Racing to check if this was a problem they new about. Come to find out, they new about the problem, and redesigned the CMI Sweep Headers for the 525's motors. Mercury Racing offered to sell me a new set Headers from one of their dealers at $8,000.00 a set. Iam aware that parts wear out, thats why we do preventive maintance, but if I would have known about this, I might not be rebuilding both engines. Please check my story for yourself, give them a call like I did, could save you a lot of money

ROCKER DOWN

I have heard of this before.I think if I had 525s I would put the stainless marine manifolds on.May lose a few HP but I can deal with that.

The problem is not with the headers that CMI sales. The problem is with the headers Mercury sell made by CMI. It is a heating and cooloing issue with the type of stainless Mercury specified that cause the welds to crack due to the specified material.
The worst part of the problem is Mercury also changed the location of the bolt holes in the head and the header so you are stuck using the crappy material Mercury has specified ( this is unless some one has comeout with headers with that have these new bolt locatioins that I am unaware of).
Allen

I always though you were stuck with what it came with also.But Pantera put Stainless marine exhaust on the 41 with 525s they built.

Just visited stainleass marines site and they do not mention it. I bet the changed heads or re drilled the 525 heads. Either way not a drop in change out.
Allen

I met with Jerry at Stainless Marine about 2 weeks ago. He has replacement manifolds and risers to fit the 525s. In fact he was doing a retrofit on a pair for Lipships. They looked very nice.

No scrub in HP is claimed as well.

I think they are worth looking at.

Thanks to all, at this point I could use the help.

ROCKER DOWN

We can repair the ones you currently have. This has been a well known problem of the 525's since they came out.

Happens all the time on these things. Stellings also makes a replacement set, that are apparently a lot better than the CMI's

Shocker...