I have a 5411 in my 1980 Catalina 27. My exhaust
spits out very little water until the engine gets up to 150F. As I motor along the temp gauge will increase slightly over the 150F and then come back down. When the temp increases I get a lot more water flow out the exhaust
and then the temp backs down to 150F. My engine runs consistently at the 150F mark. I have had people yell to me that I have no water flow out the exhaust
thinking something is wrong like my intake valve is closed.
When I winterized my engine this year I had the marina do the job. They hook up a rubber coupling that covers my intake screen under the boat and then I started the engine. In this case I had water running out the exhaust
continuosly and the engine temp only got up to about 125F. I must have had a lot more water bypass the thermostat than normally occurs when operating the engine with the boat in the water.