Re: 4.3L OMC thermostat removal and replacement help.
that's where it is supposed to be, you have to understand how the system works... it really is 2 systems.. Most people think the system works like a car, where cold water is passed in to the top of the engine from a radiator.. in the case of a raw water cooling system, the t-stat is actually keeping the water in the engine, until it is hot enough to be pushed out in to the exhaust cooling system.
If the engine is cold, the thermostat assembly routes the water to the exhaust risers where it is passed overboard through the exhaust. The water contained in the engine remains in essentially a closed circuit moving from the engine cooling passages to the thermostat assembly to the engine circulating pump then back to the engine cooling passages. This closed circulation allows for a quick warmup.
As the temperature of the water passing through the thermostat assembly increases, the thermostat begins to open allowing the hot water to be sent to the exhaust manifolds where it is discharged overboard. The thermostat assembly also allows the incoming cold water to mix with the hot engine discharge water, this cooler water is now routed to the engine circulating pump then to the engines cooling passages.
This system uses the thermostat to maintain the engine within operating parameters. As the water temperature fluctuates the amount of cold water added to the engines circulating system is controlled by adjusting the discharge path of the water. If the engine is too hot, water is allowed to discharge via the exhaust manifolds and more cold water is introduced into the engines circulating system. If the temperature is too cold, the cold water bypasses the engines circulating system and is discharged overboard through the exhaust risers
