Reply To: no water flow 63 evinrude 40hp big twin

[Don]

First, how are you test running the engine? In a bucket, on a flushette, on the boat in the water? Next, what makes you think it is not pumping water? Did it pump before you pulled it apart?
The engine has to be sunk pretty deep in a bucket before it will pump properly. Keep in mind that you won’t see much water flow from the upper exhaust relief even though the engine is pumping properly. You will see a little more spray when the thermostat opens up. Is the engine actually overheating? Keep in mind that there is a plastic check valve and spring in the thermostat housing that must be in place and operating properly, or the cooling water will just “short circuit’ back to the pump without circulating through the block.
The engine is new to you, does it appear to have been over heated (discolored/blistered paint or melted wiring)? I don’t mean to throw all these questions at you, I just don’t want you to go crazy trying to fix something that might not be broken. You have had the gearcase off, so you know there are two water tubes, and you indicate the water tubes were correctly seated in the impeller housing. You mentioned the impeller “looked OK”, did you replace it with an OEM or aftermarket impeller? How did the inside of the impeller housing look? A worn/grooved/corroded impeller housing will keep the engine from pumping properly even with a new impeller. Again, this is a somewhat complicated cooling system, I just don’t want you going crazy trying to fix something that isn’t broken….D