Mercuriser 260 overheat at low speed

[alldodge]

Find one at Lowes or HD, and online under $30. Could do it the hard way and use a cooking thermometer. Take a hose clap or something else and clamp the end of it to the thermostat housing. Could also hold it in place by hand

 

[rlander06]

That's good, how about the IR temp?

Here are some of the results with the IR check.
1) Top of thermostat housing 201 degrees
2) Water pump on engine 195 degrees
3) Risers 143 degrees (both)
4) Exhaust manifold 190 degrees (both)
This is after about 30 minutes of run time.

 

[alldodge]

I'm assuming you have an alpha drive and not a TRS.

You have a restriction someplace or the impeller is not pumping correctly. The risers should be much lower in temp because if everything else is clogged up, then the risers would get all the excess cooling water. The temps are showing that the impeller and pump are not moving enough water.

Look at the power steering cooler, has it been back flushed?

Do you have check balls in the thermostat housing? These check balls are not causing the issue, but need to know if they are there.

 

[rlander06]

I'm assuming you have an alpha drive and not a TRS.

You have a restriction someplace or the impeller is not pumping correctly. The risers should be much lower in temp because if everything else is clogged up, then the risers would get all the excess cooling water. The temps are showing that the impeller and pump are not moving enough water.

Look at the power steering cooler, has it been back flushed?

Do you have check balls in the thermostat housing? These check balls are not causing the issue, but need to know if they are there.

The power steering cooler has not been flushed. I will check that next. The check balls are there and in place.

 

[rlander06]

The power steering cooler has not been flushed. I will check that next. The check balls are there and in place.

I just removed the power steering cooler and it is clear all the way through. The only thing that has not been checked is the water circulating pump. Could that pump have anything to do with the overheating problem?

 

[alldodge]

I just removed the power steering cooler and it is clear all the way through. The only thing that has not been checked is the water circulating pump. Could that pump have anything to do with the overheating problem?

Yes it could cause motor overheat, and do check it. Remove the large hose and look at the pump vanes. Stick something in there to lightly hold the vases and see if you can rotate the pulley by hand

Not to sure it is that pump because the risers are hot as well. Even if the pump had broken vanes the drive pump should still move enough water to keep something cool.

 

[rlander06]

I'm assuming you have an alpha drive and not a TRS.

You have a restriction someplace or the impeller is not pumping correctly. The risers should be much lower in temp because if everything else is clogged up, then the risers would get all the excess cooling water. The temps are showing that the impeller and pump are not moving enough water.

Look at the power steering cooler, has it been back flushed?

Do you have check balls in the thermostat housing? These check balls are not causing the issue, but need to know if they are there.

I removed the thermostat housing again to make sure it is in properly and this is what it looks like. I see that the gasket covers a water port, not sure if that is the right gasket or should it be the other style?

 

[alldodge]

This is where the manuals are not mush help. Manual 3 and 9 show the same setup. Has 3 gaskets used in that area, 2 paper and 2 stainless steel. I believe the older design used a sleeve with a slot in it which sat on top the thermostat.

So using a solid pieces there is creating a restriction, so need to use the gasket with the slot. This way there is always water moving toward the exhaust.

Do you have 4 or 6 hoses on the thermostat?

 

[harringtondav]

An earlier thread mentioned testing the drive's impeller pump output. Here is the process in my Manual #18. I checked #17 for the V8's and it had the same process and chart.

View attachment Pump output 1.pdf

 

[rlander06]

This is where the manuals are not mush help. Manual 3 and 9 show the same setup. Has 3 gaskets used in that area, 2 paper and 2 stainless steel. I believe the older design used a sleeve with a slot in it which sat on top the thermostat.

So using a solid pieces there is creating a restriction, so need to use the gasket with the slot. This way there is always water moving toward the exhaust.

Do you have 4 or 6 hoses on the thermostat?

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It has 4 hoses

 

[alldodge]

That works, do replace that gasket with one with a slot

 

[rlander06]

That works, do replace that gasket with one with a slot

Thanks, I will get one and try it out. Will let you know the out come.