Originally Posted by CrazyRu
Do you have waterflow through the engine or all water goes through the bypass line?
Rubber hose in front of the engine, from front zinc housing to collector is a bypass line. Plug it somehow, remove the thermostat and try to run the engine. Most likely you will get no or very little water. If so, your engine is blocked by buildup. If water is running freely, you need a new thermostat.
I did as you suggested and plugged the hose going into the upstream side of the thermosat housing with a three inch long piece of 1/2 inch dowel and hose clamped it in place. Started up the motor and behold no water comes out of the exhaust. Either the exhaust manifold, three way joint, or the block is stoped up by buildup. I placed a call to Pacwest Marine and Industry Here in San Diego and a tech offered some suggestions, first off removing the three way joint that contains the foreward zinc and secondly removing the exhaust manifold for cleaning of the passages. He stated that the exhaust manifold is the most commonly blocked. I am trying to figgure out how to take the hose fittings off the 3 way joint as they must be removed prior to unscrewing the joint itself from the block. It almost looks like a special tool is required to do so. The tips have notches on them. It looked like I could almost use a 3/8 flat blade screwdriver but the blade is not wide enough by about 1/8 of an inch(any ideas on that one?). I will be taking the exhaust manifold off tomorrow morning.
Many thanks to everyone for their help. Without you this would have taken me longer to figgure out.