heavyhauler

I had same problem with cmi's and silent choice on rear cylinder(s). My engine man claims the water got injested when starting the boat on silent choice, and was adamant that it be eliminated on any motor that has radical camshafts. I'm eliminating the silent choice per his instructions, when the motors are finished, but can't tell you yet if that is fact or myth.

RaggedEdge

I would think you could warm them up with a torch while they were under pressure and see if that changes anything. If I'm not mistaken here, most claim the leaks are at the flange where the pipes are welded up. Seems like that area would be fairly easy to heat up. Does your boat have the silent choice option?

I really interested in this, seems like it pops up all the time in relation to the 525's with the CMI swept back style headders. I'm shopping for my next Fountain now and everything I'm looking at is in the '04 to '06 range and has the 525's. Hate the thought of having to deal with this after spending 150 - 200K on a boat. Anyone know if it is for sure the headders or is it the silent choice???

gerritm

I don't have silent choice on this boat. The 525's do have a fairly radical cam though. I did have a broken/ cracked spark plug on that cylinder. If it does not fire, could the cylinder suck water back.

Does anyone know if there is a better set up for the exhaust tips than those cheap flappers to prevent any water coming back through the tips when coming off from plane or backing up.

THLWL

In our area where Gerrit and I boat, here is what has happened this boating season with 525 efi's built around 2005 time frame.
1. I lost 2 engines where valves stuck and popped the piston at 112 hours. Issues started at 90 hours though.
2. 1 Formula lost 1 engine at 130 hours.
3. 1 Formula lost 1 engine at 75 hours.
4. Gerrit has lost both engines at about 90 hours.

None of the above came up with a clear cut answer as to why. My headers do not leak. My repairs consisted of increasing valve guide to stem clearance, upgrade to Crane severe duty lifters, and removal of Corsa Capt. Call exhaust. There is something going wrong with 525 efi's in our area but after I spent 15 weeks of downtime researching, did not get a decent answer for any involved (Merc. Racing, Corsa, Boat builder, etc.). After several thousand spent, I'm just hoping it doesn't re-occur!

On Time

I have only had to fix a pinhole leak on one of the STBD header tubes on my STBD engine with no actual engine issues as of yet. The header was sent back to CMI who fixed it and supposedly pressure tested it before sending it back. I am following this thread with interest.

txlefty

I had a similar problem with my CMI's, the weld by the flange. Hair line cracks where the pipes were welded to flange. Found them when I put them under pressure with a hose. I took them to a local welding shop, we heated the pipes and they expanded to show the cracks and had them grind off old weld and then re-weld. Seemed to be alot "thicker" weld than from the factory. Cost me $90.00 and seems to be holding fine. Just my .02....

RaggedEdge

I would think that it could suck water back, in the absence of any combustion there would not be the normal cylinder / exhaust pressure, might well let it pull water back.

There are thru hull tips that have an internal flapper/baffle set inside the pipe itself. You also run the external flapper with these and that gives you somewhat double the protection. The other option would be the Drew Marine Shotgun Silencers, they also act as a baffle/flapper, On my Velocity I ran the internal baffles combined with the Shotgun silencers.

I really don't understand the CMI problem, I had the CMI Elbow Tops on my 525 SC's in the Velocity, put them on in 1997, sold the boat three years ago and the guy is still running them, neither of us have ever had any issues. I was fresh water only, but he runs salt water some. That's ten seasons of use, admittedly our season is shorter up here, but still it's a long time.

Question here........... are all these failures at the #8 or #7 cylinders???

Thunderstruck

Are the 525's normal BBC firing order??

Tom

On Time

As for as I know, and I have to talked to some of these guys, all are stock non-modified 525's. We are developing a picture that might have to do with the type of water, fresh vs. salt, but we need more information. Seems few of the failures come from fresh water users.

tomtbone1993

iTrader: (3)

you have any pics of the broken parts? head, piston, ect...ect...What did your internal flapper look like on your exhaust tip?