Early Merc 8.1 manifold failures

lobsta1 · Post by **lobsta1** » Thu May 28, 2009 8:39 am

Heads up to those who repowered with the Merc 8.1s. Saw this on the hull truth. Merc used aluminum manifolds for the first few years on these engines. They are corroding right through. Here is a link on the Sea Ray forum about these problems. Al http://www.clubsearay.com/forum/showthread.php?t=6038

IRGuy · Post by **IRGuy** » Thu May 28, 2009 3:19 pm

Al... Just what are you doing reading about SEA RAYS? Go to your room!

Rick · Post by **Rick** » Thu May 28, 2009 4:30 pm

Doesn't sound much different than my 454's. If gas is what you want, Crusader is the engine you want. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

Post by **Admin** » Thu May 28, 2009 8:56 pm

Do manifolds last more then 3-4 years regardless? By "early failure" how long exactly do you mean?

lobsta1 · Post by **lobsta1** » Thu May 28, 2009 10:01 pm

For RWC manifolds, I always figured 7 years & 4 > 5 years on elbows. From what I have read, these are going in 2 > 3 years with holes right through them. They were aluminum manifolds with stainless elbows & RWC with FWC in the block only. Sounds like a recipe for disaster. Merc made a running change during the 2004 model year. However, one guy repowered in Oct 05 & his are gone already. Another guy has a 2005 SR & has lost one engine & the other was ready to go. Merc still sells these exhaust systems as OEM replacements. Al P.S. When did Tim Stamm repower with these engines? What about Bob Stansell in Cohasset, Ma?

Post by **dougl33** » Fri May 29, 2009 5:00 am

Tim used Crusaders and he re-powered back in 2005. I think Bob re-powered in 2006 or 2007. Dave, As you still have the original Merc 454's you will be fine. Those manifolds were freshwater cooled. I am with Al that you should replace your exhaust elbows/risers every 5 seasons regardless of the condition they appear to be in. I know a lot of guys will run them until they fail, but they are not meant to last forever and things rarely fail when its convenient for you.

Bob S · Post by **Bob S** » Fri May 29, 2009 9:12 am

I repowered in winter of 05 with Merc 8.1. In general they have been great and I am very pleased with the performance. The only problem I have had was that one of the fuel coolers (alum) coroded and had to be replaced. Merc gave me a new cooler but did not cover the install. Actually the install wasn't the expensive part, the most difficult part was the time I spent with the yard trying to figure out the problem. As for manifolds I am not sure if steel or alum. I guess I can put a magnet on them this weekend and see.

Bob S · Post by **Bob S** » Sun May 31, 2009 6:11 am

Ichecked and they are alum I have the yard checking with Mercruiser now to see if they will replace