stupid question about thermostat...

[bass7man]

Hi, I have a volvo penta AQ131A. I believe my thermostat is bad. Do you have to replace it? Or can it just be taken out and not replaced. A few guys said to just take it out and not replace. Thanks

 

[alldodge]

Re: stupid question about thermostat...

Hi, I have a volvo penta AQ131A. I believe my thermostat is bad. Do you have to replace it? Or can it just be taken out and not replaced. A few guys said to just take it out and not replace. Thanks

Howdy
There are differences between automotive and marine environment. In the auto industry your engine is running in an enclosed systems and if the engine never reaches optimum temperature, you will burn a bit more gas but that's about it. The system being closed allows for no hot spots.

In a marine environment and you do not have a closed system, there will be hot and cool spots. The cool spots will be OK for the most part, but the hot spots are bad due to they are not getting sufficient coolant (possible air pockets). Hot spots will cause damage to internal parts or the engine. Thermostats are cheep

 

[JustJason]

Re: stupid question about thermostat...

You absolutely have to have a thermostat in the engine. It acts as a restrictor and slows down the flow of coolant/water inside of the engine, and allows it to pick up heat. Without one in place, the engine can overheat internally, which is different than what it might show on your temp gauge.

 

[bass7man]

Re: stupid question about thermostat...

THANK YOU! I was really on the fence about it. It didn't sound right to me. Thermostat it is!

 

[Alan Lloys]

Re: stupid question about thermostat...

I recommend the thermostat as well - but want to just explain to you that the AQ131 engine is a bit different than many other engines.
It does in fact have a closed cooling loop similar to an automotive engine. The thermostat works just like on a car.
There is an internal loop of coolant (should be same as automotive coolant) that circulates through the engine with the circulation pump similar to an automotive water pump.
When the engine reaches temperature the thermostat will open and allow part of the coolant flow to go through the heat exchanger. In automotive terms this takes the place of the radiator. The heat exchanger has sea water running through it on one side too cool the engine coolant. On the front of the engine you will notice that you have both a circulation pump and a sea water pump.
I actually really like this system as it is super easy to winterize and you do not ever run the risk of cracking the block in a freeze event.

Anyway if you remove the thermostat you will cool the engine coolant all the time and will probably never get up to proper engine temperature. Not dangerous to the engine but it will operate better when run at proper temperature.

The AQ 4 cylinder engines are actually marinized versions of the Volvo automotive engines. Yours I believe is a B23 block which is similar to what you find in Volvo 244 vehicles.
There are many components you can find much cheaper from the auto store for these engines. Make sure you do not use automotive parts for any of the electrical systems though - here the special marine versions are ignition proof which is required on a boat.

 

[JustJason]

Re: stupid question about thermostat...

It does in fact have a closed cooling loop similar to an automotive engine. The thermostat works just like on a car.
There is an internal loop of coolant (should be same as automotive coolant) that circulates through the engine with the circulation pump similar to an automotive water pump.

The engine runs nothing like a car engine. Marine engines are constant load engines. Car engines are variable load engines. In a boat, the engines combustion chambers run a heck of a lot hotter than they do in a car because of that constant load. Because of that the cooling system is more critical. It's not just about "how hot" is something getting, it's "how even".

 

[gm280]

Re: stupid question about thermostat...

Just for information...not all marine engines have thermostats. My OB '76 40HP Johnson doesn't have one and it works find without. SO, if your engine was designed with a thermostat, replace it, if it was designed without one, then don't worry about it either... The design engineers figured all that out during the prototype buildings and testing stages...

 

[Alan Lloys]

Re: stupid question about thermostat...

The engine runs nothing like a car engine. Marine engines are constant load engines. Car engines are variable load engines. In a boat, the engines combustion chambers run a heck of a lot hotter than they do in a car because of that constant load. Because of that the cooling system is more critical. It's not just about "how hot" is something getting, it's "how even".

I fully understand the difference in the application.
What I mean is that many if not most marine engines circulate raw seawater through the engine block for cooling.
The AQ131 engine does NOT. It has an internal loop coolant loop that is entirely separate from the sea water.
One of the reasons for this is that it is in fact a car engine that has been slightly modified to function as a marine engine.
I just wanted to give the analogy that most people are familiar with in a car.

In a raw water cooled engine the thermostat opens and lets water into the block for cooling.
In the separate loop engines the thermostat lets the coolant go through the heat exchanger where it is cooled by sea water.

There is a better explanation of the difference here: https://www.marinepartseurope.com/sv/volvo-penta-c10-cooling-system.aspx