Merc MPI MAG. 5.7 overheating

[EAVES]

5.7 Mag MPI. Bravo 1 with low water pickup.
It chewed up the impeller & it didnt melt the exhaust couplers on the riser or the Y- pipe . after running the engine st idle for 10-12 mins it will set off the alarm at 196 ( on the scanner) New complete OEM pump was installed . All hoses appear to be clear and no restrictions .. If you bring it up off of idle it will cool like it has a volume issue .. Or at idle if you pull any hose off of the thermostat housing it will immediately drop yo 170-175 degree... Any input on this would be appreciated .. This is in an Azure , so its a very hard engine to work on the cooling system

 

[Fun Times]

Re: Merc MPI MAG. 5.7 overheating

5.7 Mag MPI. Bravo 1 with low water pickup.

Hi there, Does your bravo drive only offer the low water pickup or does it have side water pickups as well?

There's a good chance the rubber parts from the impeller has made it to the thermostat thus interfering with the cooling system.

The only way to really know would be to pull the thermostat housing and have a look.

Also carefully check the backside of the impeller housing to see if it feels warm to he touch.

 

[EAVES]

Re: Merc MPI MAG. 5.7 overheating

Tonite I flushed everything again .. Thermostat housing is clean ..

I removed the down pipes to see the shutter assembly's and they are still there too ... It must have not gotten too terribly hot .. Only thing I found tonite was some large chunks of rusty metal or casting slag came out of the port side manifold ..

The one thing that does have me wondering is why this OEM pump assembly came with a plastic inlet/outlet plate and every OEM one I've done so far was a complete brass pump and plate ..

The bravo does have both side pickup and low water pickup

Thanks on the reply

 

[Fun Times]

Re: Merc MPI MAG. 5.7 overheating

The one thing that does have me wondering is why this OEM pump assembly came with a plastic inlet/outlet plate and every OEM one I've done so far was a complete brass pump and plate ..

Sounds like you received the new style impeller housing cover kit. The plate is plastic with stainless steel ware plate. Should be better and last a bit longer. Item #10,
http://www.mercruiserparts.com/Show...=15322&bnbr=300&bdesc=Sea+Water+Pump+Assembly

The bravo does have both side pickup and low water pickup

When you run the engine at home on the garden hose, are you covering up the low water pickup with something like gray duct tape and using the side water pickup? if not you stand a very good chance at sucking air into the cooling system and in return damaging the impeller and causing an overheat situation.

 

[tpenfield]

Re: Merc MPI MAG. 5.7 overheating

Oil cooler is in line between the sea water pump and the thermostat housing. The remains of the impeller could be there

 

[EAVES]

Re: Merc MPI MAG. 5.7 overheating

This engine has 2 coolers . One STB side and one rear of engine up top .. Both are clear ..

The low water pickup is taped up and using the side inlets ..

Thank you on the replys

 

[thumpar]

Re: Merc MPI MAG. 5.7 overheating

How did you flush the hose out? My impeller recently blew up on my 5.7 EFI. When I backflushed mine I stuck the hose from the house in the inlet hose from the seawater pump to the thermostat housing. Lots of rubber came out.

I am not sure what you have on yours but I have all the coolers including cool fuel. You might try taking each section apart and check the hoses. I would doubt any of it made it all the way to the thermostat.