496 Mag HO exhaust manifold over heat

[FLCobalt]

I was asking about this problem and the PCM codes a year ago and just heard from the customer that the problem was never fixed. Can anyone help?

We sold a 2005 400SS Formula to a customer in Europe and they have issues with the port engine throwing the alarm. The engines are the 496 Mag HO's. Accorning to the Rinda scanner it's both the port and stb side exhaust manifolds overheating in the port engine. The raw waterpump impeller is new, the thermostat is the correct one and new and it looks like the raw water is circulating fine when looking at the through hull exhaust when it's open. The overheating happens only on higher RMP's after about 10 minutes. The temperature gauge it self goes only to about 195 degrees but then the alarm goes off. When they idle and let it cool down it actually goes all the way down to about 155 degrees. The Stb engine stays at steady 180 degrees all the time, idle or high Rpm's. The boat is in Europe so we have no way to go and check it our selves but we would like to help the customer out. Does anyone have any experience in something like this? The boat had about 140 hours when he got it and this started right away. All the help and ideas are welcome. Thanks!

 

[havasuboatman]

Re: 496 Mag HO exhaust manifold over heat

My first thought would be a piece of an old impeller caught in the oil cooler. You said the impeller is new, were all of the pieces of the old one removed? What is the condition of the fresh water pump housing? is it scored? It doesn't take much wear to drop water pessure. Was the drive banged on the bottom? Sand in the block?

 

[FLCobalt]

Re: 496 Mag HO exhaust manifold over heat

We actually changed the impellers before the boat was shipped and the old ones we still good, no pieces missing. I heard that they never back flushed the cooling system either so it is very much possible that there is crap in the system. I have no idea if the drive was banged in the bottom, it sure didn't look like it when the boat left the states. I'm guessing it is either some crap in the raw water side or possibly a collapsed water intake hose in the gimbal housing. I told them already to look for both so now it's just to wait and see. Thanks for the input.

 

[Don S]

Re: 496 Mag HO exhaust manifold over heat

I would be looking for an air leak on the suction side of the raw water system.
If those engines have the air actuated drain system on the back of the pump, make sure all the air is completely released. Especially on the valve on the intake side of the raw water pump.