Overheating 2001 Mercruiser 5.0

[rick3452]

I just went through this....... My issue turned out to be a lack of water being supplied to the motor. The inlet hose can restrict the amount of water. I installed a Through Hull Water pick up and it Completely solved the problem. Good luck!
Rick

 

[Bt Doctur]

But to do that you need an engine mounted raw water pump

 

[rick3452]

Of course ! Duh

 

[Bt Doctur]

He has the GEN II that could have dislodged the water inlet tube or has damaged O rings on the inlet tube. Using a hose in the housing may isolate his trouble to the engine or the drive .

 

[WhataBunch]

He has the GEN II that could have dislodged the water inlet tube or has damaged O rings on the inlet tube. Using a hose in the housing may isolate his trouble to the engine or the drive .

I have the drive off now and have just finished flushing it. The hose would only run a few inches into the inlet before it felt like it was hitting something. I did notice the left side of the transom was moving 2 or 3 times as much water as the right side. Additionally, I don't have a o-ring around the inlet as in the pic. I thought it may have fell out when I pulled the drive, but it's no where to be found.The crazy thing is this boat ran great all last season and the first time out this season before the problems began.

 

[Bt Doctur]

The crazy thing is this boat ran great all last season A-B and the first time out this season before the problems began.
So what was done to it between A and B
The hose will only go in a few inches because of the bend in the hose. Did the motor temp stay normal with the hose?
Water exiting only on 1 side could mean a manifold/riser is clogged up.You could blow thru the hoses that go to the bottom of the manifolds to see if you can blow air thru them.

 

[WhataBunch]

The crazy thing is this boat ran great all last season A-B and the first time out this season before the problems began.
So what was done to it between A and B
The hose will only go in a few inches because of the bend in the hose. Did the motor temp stay normal with the hose?
Water exiting only on 1 side could mean a manifold/riser is clogged up.You could blow thru the hoses that go to the bottom of the manifolds to see if you can blow air thru them.

After the first trip this season, the boat was put back in a storage building for a couple of weeks. Nothing mechanical was done.

I did not start the engine, I only ran the water into the inlet. Are you saying it's OK to run the engine with the drive off and the hose supplying the inlet?

 

[Bt Doctur]

Yes, you can run the motor forever while adding water to it.All the hose does is simulate a drive hooked up.Turn the water on all the way, start the engine.
You dont have to worry about the rpm because the drive is not connected. On muffs you really cant go much above 1500 rpm without damaging the impeller
If it reacts with normal temps, and the manifolds and risers are somewhat slightly warm to the touch, the trouble is in the drive
check your messages.

 

[WhataBunch]

Yes, you can run the motor forever while adding water to it.All the hose does is simulate a drive hooked up.Turn the water on all the way, start the engine.
You dont have to worry about the rpm because the drive is not connected. On muffs you really cant go much above 1500 rpm without damaging the impeller
If it reacts with normal temps, and the manifolds and risers are somewhat slightly warm to the touch, the trouble is in the drive
check your messages.

I ran it with the hose in the drive and it warmed up to operating temp but did not overheat. I did notice a big difference in the temp of the risers. The driver side was pretty warm while the passenger side stayed surprisingly cool. At idle it warmed up to about 175 degrees (160 thermostat installed) and as soon as I raised the RPM to about 1800-2000 it would almost immediately react and drop 15-20 degrees. When I squeeze the hoses at the thermostat housing, I can feel water flowing through both of the passenger side hoses but it feels like very little flowing through the driver side hoses.

 

[WhataBunch]

Well, I finally found my overheating problem. It turns out that the water inlet hose that runs through the bell housing into the transom next to the bellow had come loose. While it appeared the water was coming out of the exhaust, it was actually just being picked up by the impeller and splashing off of the bell housing. I hope this will help someone that may have the same problem as I did.