Hey boat guys...

[ptindall]

Is it common practice to not run a thermostat and let your engine stay stone cold? When I bought my boat, it had no thermostat so I put one in it. Next time on the water the engine warmed up great. Next time out it was stone cold again. I mean after running for at least 30 minutes straight I could put my hand on the intake manifold and valve covers and it was just like the engine had never run. So I'm telling my buddy this at work and he says, "sounds good to me, I know people with big block boats who don't run a thermostat." :skep:

So now I'm not sure if I should dig into it again and figure out why the brand new thermostat is stuck or just leave it alone.

It's an '83 305 Chevy.

http://i209.photobucket.com/albums/bb128/01Z06guy/jeepandboat007.jpg

http://i209.photobucket.com/albums/bb128/01Z06guy/jeepandboat003.jpg

[Scissors]

Physics doesn't magically change just because an engine is on a boat. Running without a thermostat is retarded.

When water-cooled engines are designed, it's with the understanding that they will operate within a certain narrow temperature range. Therefore tolerances, oil viscosity, etc. are all designed/recommended around this given. So if you're running too cool, tolerances will be too loose. Not to mention that cylinder walls with a 160 degree thermostat wear approximately twice as fast as they do with a 180 degree thermostat.

[Bingo Fuel]

Always ran with a thermostat for the FWC 302 and 351.
They run efficiently at 160 - 190.
Plus, the cabin heat was nice in the winter.

[ptindall]

Physics doesn't magically change just because an engine is on a boat. Running without a thermostat is retarded.

When water-cooled engines are designed, it's with the understanding that they will operate within a certain narrow temperature range. Therefore tolerances, oil viscosity, etc. are all designed/recommended around this given. So if you're running too cool, tolerances will be too loose. Not to mention that cylinder walls with a 160 degree thermostat wear approximately twice as fast as they do with a 180 degree thermostat.

That's what I was thinking. But I've never had a boat or really had any friends with boats so it's all new to me. Combine the fact that my boat previously didn't have one and the statement from the first person I mentioned it to got me wondering about it. And while physics don't change for a boat engine, the running conditions do. You don't regularly run 80% throttle at 4000rpms for extended periods in a car. I thought maybe people let the boats run cold to help keep the combustion chamber temps down or something. :bilmem:

[Scissors]

That's what I was thinking. But I've never had a boat or really had any friends with boats so it's all new to me. Combine the fact that my boat previously didn't have one and the statement from the first person I mentioned it to got me wondering about it. And while physics don't change for a boat engine, the running conditions do. You don't regularly run 80% throttle at 4000rpms for extended periods in a car. I thought maybe people let the boats run cold to help keep the combustion chamber temps down or something. :bilmem:

If the engine is properly designed, it'll have appropriate coolant galleries to carry enough water past the hot parts to carry the heat away. The only limiting factor for dealing with the heat is having a large enough radiator with enough air flow to remove the heat from the coolant.

All a thermostat does is determine the minimum operating temperature--but the engine is designed for a range. If the galleries, radiator, and/or airflow aren't sufficient, then you're going to run too hot whether you have a thermostat or not. The thermostat only really comes into play if you're running too cold.

There is one effect which should be noted in regards to thermostat removal, and that's that the loss of its restriction can (assuming there's nothing more restrictive within the system) increase flow rate. However, contrary to popular belief, increased flow rate doesn't result in higher temperatures, but rather a smaller temperature delta. Coolant spends less time in the radiator being cooled, but it also spends less time in the engine being heated, so the coolant's temperature fluctuations are lessened.

This is all assuming a closed (fresh water) system. Boat engines which are cooled with river/bay/sea water, by definition, start off with coolant that's much colder than closed systems would.

[ptindall]

If the engine is properly designed, it'll have appropriate coolant galleries to carry enough water past the hot parts to carry the heat away. The only limiting factor for dealing with the heat is having a large enough radiator with enough air flow to remove the heat from the coolant.

All a thermostat does is determine the minimum operating temperature--but the engine is designed for a range. If the galleries, radiator, and/or airflow aren't sufficient, then you're going to run too hot whether you have a thermostat or not. The thermostat only really comes into play if you're running too cold.

There is one effect which should be noted in regards to thermostat removal, and that's that the loss of its restriction can (assuming there's nothing more restrictive within the system) increase flow rate. However, contrary to popular belief, increased flow rate doesn't result in higher temperatures, but rather a smaller temperature delta. Coolant spends less time in the radiator being cooled, but it also spends less time in the engine being heated, so the coolant's temperature fluctuations are lessened.

This is all assuming a closed (fresh water) system. Boat engines which are cooled with river/bay/sea water, by definition, start off with coolant that's much colder than closed systems would.

I'm with you 100% on every bit of this for a car and it's amazing how many people fail to understand this when it comes to thermostats. But we're not talking about not running a thermostat on an overheating car. Let's make the assumption that using an automotive engine designed for use in a car doesn't quite provide enough cooling capacity to combustion chambers due to the fact that it's not designed for heavy load, high RPM use for extended periods of time. Going without a thermostat will increase the flow and drastically decrease the coolant temp in the heads and block in a boat sucking lake water, which will, in turn, decrease the combustion chamber temps under heavy load. I'm not saying that's the case, I'm saying it's a realistic possibility and why I thought the question is worth asking to those who have BTDT. :cheers:

The added engine wear might be worth it on an engine only run a few dozen hours per year as opposed to melting pistons and spark plugs if you can have the fun of running the boat hard.

[w!ngnut]

I've only owned two boats and always ran a thermostat in both so I honestly don't know the answer.

I just felt like posting to help my count. :lolsmile:

[Scissors]

I'm with you 100% on every bit of this for a car and it's amazing how many people fail to understand this when it comes to thermostats. But we're not talking about not running a thermostat on an overheating car. Let's make the assumption that using an automotive engine designed for use in a car doesn't quite provide enough cooling capacity to combustion chambers due to the fact that it's not designed for heavy load, high RPM use for extended periods of time. Going without a thermostat will increase the flow and drastically decrease the coolant temp in the heads and block in a boat sucking lake water, which will, in turn, decrease the combustion chamber temps under heavy load. I'm not saying that's the case, I'm saying it's a realistic possibility and why I thought the question is worth asking to those who have BTDT. :cheers:

The added engine wear might be worth it on an engine only run a few dozen hours per year as opposed to melting pistons and spark plugs if you can have the fun of running the boat hard.


If your engine is failing in stock trim from running open throttle at high RPMs for long periods of time, then you shouldn't have purchased a Kia.

:dance:

[War Eagle ZO6]

The main reason a thermostat is needed in a open raw water system is to get engine to operating temp.