Thermostat direction

[Mic]

I have been chaseing a temp. problem for a while on a new to me Cat. 27 with a 5411 Diesel. No, not running hot but running cold less than 100 degrees. I took the thermostat houseing off and found that the thermostate was stuck closed. In my opinion it should have been running hot not cold. I need some help on this one. I put a new thermostate in and now the engine runs at about one fifty ideling and goes down to 140 when I bring the RPM up, sounds about correct according to the operation manual that I have.The problem that I have, or don't have? is that there was more water "burping" out the exhaust pipe when the engine was running cold than there is now that it seems to be operateing correctly. Could I have installed the thermostate upside down? and also what size hoses should be in the system. Thanks  "MIC"

 

[Jack Swords]

5411 cooling

The thermostat is restricting water flow through your engine to allow the raw water to recirculate and therefore attain a higher temperature. That is its function. Before the thermostat was allowing raw water to flow unrestricted through your engine and out the stern and therefore not heated. Now, you are getting correct temps for the 5411 engine and less water is flowing.

 

[Mic]

Thermostat

Thanks Jack for your reply.Can you think of any reason why They/someone would run 5/8 inch water hose from the seacock to the water pump then from the water pump to the engine block with 1/2 inch then out of the top of the thermostat to the exhaust riser with 5/8 inch and out of the bottom of the thermostat back to the mixing "T" with 1/2 inch line. I was under the impression that "once restricked always restricked" It appears that I am winning this battle as it does register on the gage correctly and the engine water pump is warm but not hot. Thans again for your help "MIC"

 

[Jack Swords]

Hoses

Mic, we are home in the US now so I am not certain of the hose diameter, but am certain they are all the same as I replaced them all several years ago. The engine manual is down in the boat too. I suspect 5/8, but certainly larger would be better than smaller if in doubt. The only restriction would be the thermostat. The nipple size on the engine and thru hull should determine the hose used. If the difference between 5/8 and 1/2 is only 1/8 inch, they could have been forced on the nipple leading to potential splitting under the clamps. For the minimal cost, I'd replace them all and double clamp them. But, do take a hose off and see what the nipple dictates. You can also call the Catalina factory to verify the hose sizes. Thinking about this, I think it's time to replace mine too. Glad the temps are down where they should be. Funny cooling system on this engine, but they sure are tough.