I want to thank all the OSO 150 replies about the problems CMI & Mercury Racing are having with their 525s Headers. What an education, Both engines have been rebuilt because of the leaking headers, and now, I must decide on which new Exhaust Headers to buy. Thanks for the

Rocker Down

Why don't you just buy the big block headers from cmi and take them to have'em drill an extra hole or two in the flange?

In other words, the non-525 headers are fine. It will take longer to setup then to drill the holes..

Gen-X ????? Maybe next time Merc will leave the header specs to the header folks.....

I replaced mine with Gen-Xs and am very pleased. If you have staggered motors, most likely will need to brace one motor.

stellings

I surely wouldn't buy CMI's if you starting over.

drill & tap your heads for stainless marine exhaust & be done with it.

X2 on the STAINLESS MARINE !!!!!!!

+1,,,spend the xtra coin on the stelling's..

why are we into an other thread about this product......
you want them to last......
TAKE THE TIME TO WARM THEM UP!!!!!!!
TAKE THE TIME TO WARM THEM DOWN!!!!!!!!!!
IF YOU NEED A LESSON ON METALLURGY
i only charge 65 an hr
no seriously.....CMI are a reasonable product..... for the average hp boater
the problem occurs with temp..... overheating of the welds and rapid cooling of water injection at those points
stellings are a better product.... and if you pay $4000 for CMI you will pay $8000 for stellings the math is quite simple
if anyone needs a more detailed diatribe PM me

I think what you may not be realizing is that specifically, the 525 headers from Merc with a Merc part number is a different quality piece than any other "NON-MERC" CMI part.

Merc told them to make the header cheaper by using less heat treating etc....

In part, this lack of info is what keeps the topic going.

All the other CMI headers are better than the Merc Branded CMI..

Your suggestions regarding the use and taking the time to heat up or cool down is a great idea. Most guys jump out of their diesel truck and slam the door with an 800 degree turbo baking itself to death..

Do you think they will be concerned about a "water cooled" part on a boat?