Originally Posted by
mmandley
I understand but the engine is full of very small passages for the water, and the water pump pumps it through at very high pressure, close to 4 gallons a minute, so using a garden hose that is 1 inch in diameter to push water through a 1/4 inch at best hole is going to create a natural back pressure and give you false readings.
You really need the pressure of the water pump to see if there is a blockage in the engine.
Also you cant test water flow through an engine with the T stat installed because it required the engine to heat up to 140 before it will even start to open, so at this point you will get No water flow, and from the time it hits 140 to 220 over heating is only a minute or 2 at best.
This is why testing without the T state is important, because all you need to see is if you have water flow.
Also is your buddy the same owner of the Supra as last summer? Or did he just pick this boat up?
If he is the owner did he over heat it last summer?
If so i would replace the Impeller first, and then continue with the above TSS.
If he is a new owner of the boat then i would continue to TSS.
Normally even if you blow a head gasket it wont Stop all water flow through an engine because its not 1 path all the way through. It has 1 main inlet then braches through the heads, block and such. Other wise you would always have 1 side of the engine running hotter then the other.