496HO vs 525
05-28-2014 | 04:59 PM
#21
Forum Regulator
Joined: May 2001
Posts: 24,215
Likes: 1,613
From: Worldwide
The main issue is with the Mercury spec'd headers on the 525EFIs.
CMI submitted their header for the OEM package.
Mercury wanted something different. (read: cheaper)
CMI built what Mercury asked for.
Mercury 525EFIs are now know for leaky header issues. especially (but NOT exclusively) to boats with staggered engines, as the forward mounted engine allows for more tailpipe & header vibration. The vibrations over time cause the cracks.
05-28-2014 | 06:55 PM
#23
Gold Member
Joined: Oct 2000
Posts: 5,664
Likes: 140
From: Hollywood, MD, USA
I have a 2005 525EFI. I just replaced the CMI's with Stainless Marine at 230 hrs mainly to be proactive.
The shop that did the work pressure tested the CMI's and said they DID NOT leak.
Maybe I was lucky? I did the Merc service bulletin that eliminates the bypass hoses between the distribution rail and the tails. Also, I always drained them when not in use. They where run in a mix of fresh and salt.
The shop that did the work pressure tested the CMI's and said they DID NOT leak.
Maybe I was lucky? I did the Merc service bulletin that eliminates the bypass hoses between the distribution rail and the tails. Also, I always drained them when not in use. They where run in a mix of fresh and salt.
