260 Mercrusier overheating

[rlander06]

I have a 260 Mercruiser that has an overheating problem. All hoses are clear and new impeller installed. The water flows through all hoses except for the two on top of the thermostat housing. New thermostat was installed and I used the same sleeve that was in it. Picture are attached. Would this sleeve stop the water flow to these two hoses?

 

[scoflaw]

That sleeve could be in there wrong, can't tell from that pic. That's a crusty looking piece. Looks like the spring and ball setup, may be sticking with the corrosion you have going on

 

[rlander06]

Now I have another question. I have water coming out now after I cut out the path like I have seen on the new plastic sleeves. The engine still overheats with all hoses on but when I remove the two hoses on top of the thermostat housing, (only one at a time) the engine runs at a nice cool temperature. Could this mean I have a blocked exhaust manifold? I can blow though the hose with some pressure. After putting the hose back on while the engine is running the temperature starts to rise again.

 

[scoflaw]

Not following along on how it would run cooler with hoses disconnected, but I will say that if your exhaust system is as crusty as your other pics then they probably need replacing

 

[Bt Doctur]

thermostat appears correct , water will not flow to the manifolds until the therm opens. Therm housing itself could be the problem ,best option is the SS replacement unit .

 

[Scott Danforth]

water should be flowing all the time to the manifolds

that is what the bypass hole is for

 

[rlander06]

It seems that the water pump is not pumping water to the motor. I did put a new impeller in. with the inlet water hose off at the motor the water is not there until I rev up the engine then it starts to pump.

 

[Scott Danforth]

It seems that the water pump is not pumping water to the motor. I did put a new impeller in. with the inlet water hose off at the motor the water is not there until I rev up the engine then it starts to pump.

and how are you supplying water to the drive? muffs with the hose on full blast?

'cus if youre trying to suck up from a bucket, you toasted your new impeller

 

[kdmiller8251]

Dont forget there is also a water pump on the motor as well.. whats the condition of that?

 

[rlander06]

and how are you supplying water to the drive? muffs with the hose on full blast?

'cus if youre trying to suck up from a bucket, you toasted your new impeller

I am running water with garden hose and muffs. water at full house pressure.

 

[rlander06]

Dont forget there is also a water pump on the motor as well.. whats the condition of that?

Water pump on engine is in good shape, removed to inspect water passages and impeller all are good.

 

[kdmiller8251]

Is the water getting to the engine pump from the drive?

 

[rlander06]

Is the water getting to the engine pump from the drive?

The water is barley getting there. With the engine idling it is hardly there. When I bump the RPMs up the water volume increases.

 

[CamaroMan]

Remove the inlet water hose to the motor (one coming from the back).. point it into bilge or a bucket and idle motor. There should be a steady stream of water flowing - put your thumb over the open end and push with your thumb, there should be good pressure. If not something went wrong with the impeller change and/or its burned out from being run without muffs (10s can kill an impeller). If the impeller is fine, you might also have blockage in the cooling line. If the leg is off, put a garden hose into incoming water hose (one by the t-stat housing) and back flush. If you have a power steering inline cooler that might also be blocked as it has small tubes the water passes thru -

Basically you need to confirm that your water hose is clear from leg to motor, and that the impeller is installed and working correctly (the water flow test into a bucket/bilge will confirm this).

Im no greeny but i cant imagine how much water has been wasted on boaters (myself included) :/ I have a 400 gallon water tank at my shop and use a bilge pump inside a large storage container to circulate on long runs/tests... so it circulates..

 

[rlander06]

Here is the problem (I think) the rubber seal that goes into the top of the pump housing where the guide tube goes, was missing. this makes a seal for the water tube to sit in, without it water was not going up the pickup tube unless I had it in high RPMs. I will be testing it out this weekend once I get it all back together and will get back to everyone with the results. thank you.