Offshoreonly.com - Engine help

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Quote:

Originally Posted by MarkDonzi (Post 2348640)

Beak,

I have 525's in a staggered installation. The leaks were at the collector plate and were repaired by CMI. The headers on my boat are custom so they are not warrantied by CMI/mercury but Donzi. I boat in Ft Myers Beach Florida Salt Water in the winter and Detroit, MI Lake St CLair Freshwater in the summer. Motors are always flushed with saltaway after each use. Both sets of headers on my boat leaked at the same location. I have not had any problems since the leaks were welded by CMI. If I know the boat is going to sit for any time more than a day or 2, I drain the headers and leave the plugs out. It's easy in my motor box with the stagger. etting close to rebuild time on one motor and I will have the headers tested at that time.

Hope this helps.

Mark

MarkDonzi,

Did you get the newer "cool collar" (water jacket welded about 1/2" short of the flange) CMI's on both your engines? I got the new style only on the port motor, and the older style(welded directly to the flange) on the stbd(rear) motor. I called CMI and they told me that "a lot of staggered boats from '04 - '06 were built like that". What about yours? My understanding is that the cool collar design has less of a chance to leak water into the cylinders in case of a leak due to corrosion or weld failure. CMI would not comment one way or the other.

Does anyone know if the failure rate on CMI brand vs Mercury Racing? I was told by CMI that Mercury made them change the flange from the ones you can buy direct. I did something a little different with mine, I run engine coolant through mine except the tail pipe.

Hey Beak,

I believe mine are the older welded flange. They are identical on both motors. SInce theeywere repaired by CMI, I have not had a problem, but I also drain them religously. CMI would not discuss "failure" of their product. They were trying to get the OEM's to install supports on the forward staggered engine header tailpipes. They claim the weight of the exhaust pipe from the end of the header to the transom was causing problems. I bought into that until the rear staggered motor header leaked at the same spot. Just plain poor welding is the cause IMO.

Mark

Quote:

Originally Posted by racer-x6 (Post 2349837)

Racer-x6 - Very interesting running coolant through the headers. I guess you have it circulating somehow. Does the temp indicator on the engine remain the same while also having to cool the heat from the header/exhaust? I think if this works well, you could get a patent. You got me thinking now (I lost both 525 efi's at 112 hrs - down for 15 weeks while all involved tried to figure out what happened).

Quote:

Originally Posted by THLWL (Post 2350325)

So? What did you find out? What heppened?

No clear answer on cause. Boat mfg., exhuast mfg. and engine mfg. all had different opinions. The failure occured when an exhaust valve stuck in each engine and struck a piston. For repair, did a head job, changed to Crane lifters, increased valve stem to guide clearance to 2 thou. min., and removed Corsa Capt. Call exhaust system. It's very loud now but running. Did not appear to be header leak though.

It works well, the sea water pump brings sea water to the heat exchanger in the front of the motor and the circ. pump on the front circulates it throughout the system. the only place the salt water gets to is the heat exchanger and the tail pipes. I have been running it for two years with no issues. the temp runs about 175 deg all the time, at my store we have installed this system on 454 carb., 502 Mpi and a 500 EFI.

The 525 efi already has the heat exchanger. So it may just be a plumbing issue. I have the SmartCraft gauges, so I could monitor the heat pretty closely. I'm going to look hard at this set up this winter. Very interesting. Thanks for the feedback.

Quote:

Originally Posted by THLWL (Post 2351886)

The heat exchanger on the 496 and 525 may not be big enough and and the way the tank sits on the manifold housing you may not have a port to attach the in an out hose. If I find out any more info I'll let you know.