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Overheating 5.0 mpi Bravo - Impellor and Manifold replaced

S

smijas

New member
Hi all,

I am at a loss as to why my 5.0 mpi bravo is overheating. Engine is 5.0 mpi with bravo 2 outdrive, raw water cooled. Symptoms are overheats at idle until you increase rpm to 1500. Overheats when rpm is over 3000 and I get a water flow alarm.

So far I have:

1: replaced raw water pump and impellor
2: checked water flow through all hoses with pressurised water from tap.
3: Replaced Risers and Manifolds
4: pulled thermostat and tested in a pot on the stove - It opens and closes as expected.

If anyone has encountered this problem and had a fix it would be great to hear from you.

My thoughts now are hose from outdrive through bellows is collapsing due to suction at higher rev's. (Doesn't explain the idle overheat)
Some sort of blockage somewhere in the system that is restricting waterflow. (Must be post raw water pump and prior to water manifiold that splits water flow - so through the power steering)

Any help or ideas appreciated

Cheers
 
smijas said:
I am going to go down the path of utilising a through hull fitting for cooling water rather than fix this only for it to happen again at some point.
Hopefully that sorts it out as I have not pulled the leg off to confirm. It seems like wasted time and effort to pull the leg then put it back together along with putting in a through hull.
Click to expand...

The picture I posted shows the water feed pinched off with corrosion where the elbow bolts to the transom assembly inside the hull.

If you feel you need to jump right to a thru hull, that is up to you. You may not have this problem although it is very common. You actual water feed tube may just have a hole in it. The new water tube kits from Mercruiser/Quick Silver are redesigned to help with this issue and deliver increased water flow.

If you choose to go with the thru hull, you will need to cut out a section of the water tube inside the bell housing on the outside of the boat. If you do not do this, the drive will overheat. Get a hose barb plug and put it in the water feed line that goes to the pump. Just lay it down in the bilge below the engine, don't let it interfere with your bilge pump.
 
Had the same issue year or so ago. Put a Johnson crank mounted pump and a through hull pick and now tons of water. You just need to make sure you have clearance for the pump I believe it's 5 inches deep.
 
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