Thermostat Purpose

[Bulbash]

Just wondering what is the purpose of having thermostat in the small boat engine. Lets say if you remove the thermostat and run boat without it, temperature will be at it's minimum which should be good for the engine. Is there any purposes such as pressure or something else that I'm missing?

 

[Boomyal]

Re: Thermostat Purpose

Wow! Back to basics for you, Bulbash. There are two reasons for thermostats. Primarily it is to control the combustion chamber temperature. Fuel burns more efficiently at 180? coolant temperature and above, otherwise a good portion of it will be wasted as it washes down the cylinder walls, taking the lubrication with it and ir would accelerates cylinder and piston ring wear in the process. That all being said, you have an issue of metal expansion and contraction. Tolerances in engines are designed to assume that the metal will get up to temperatures that are suitable for combustion. Anything less than that makes everything too tight and accelerates wear. Engine lubricants are also formulated to be most effective at temperatures that are recognized as being most efficient.



Thermostats also are designed to produce a consistent temperature so that the metal is not continually expanding and contracting. This is particularly hard on any gasketed joints. I hope this dissuades you from thinking you can run without a thermostat!

 

[Bulbash]

Re: Thermostat Purpose

Wow! Back to basics for you, Bulbash. There are two reasons for thermostats. Primarily it is to control the combustion chamber temperature. Fuel burns more efficiently at 180? coolant temperature and above, otherwise a good portion of it will be wasted as it washes down the cylinder walls, taking the lubrication with it and ir would accelerates cylinder and piston ring wear in the process. That all being said, you have an issue of metal expansion and contraction. Tolerances in engines are designed to assume that the metal will get up to temperatures that are suitable for combustion. Anything less than that makes everything too tight and accelerates wear. Engine lubricants are also formulated to be most effective at temperatures that are recognized as being most efficient.



Thermostats also are designed to produce a consistent temperature so that the metal is not continually expanding and contracting. This is particularly hard on any gasketed joints. I hope this dissuades you from thinking you can run without a thermostat!

Awesome!!! That is a really good explanation, I was just thinking of solving my overheating issue with running without thermostat, but now it explains things... Thanks a lot and sorry for stupid question....

 

[Celtichawk]

Re: Thermostat Purpose

Thermostats also are designed to produce a consistent temperature so that the metal is not continually expanding and contracting. This is particularly hard on any gasketed joints. I hope this dissuades you from thinking you can run without a thermostat![/QUOTE]

Funny you say this but I have heard from old guys who worked on cars that a thermostat not in a vehicle isn't a bad thing. Not saying it was all a good thing but I have come across people who have ran without them. When it comes to a temperamental machine like boats I do not think I would risk that. Some things are there for a reason and Boomyal you explained this clearly. Boat motors are there own species and tend to need a lot of TLC. So again run one don't risk it without.

 

[Silvertip]

Re: Thermostat Purpose

Old guys who worked on cars did not understand any better than Bulbash. Ever heard of "cold seizing". I didn't think so! That can happen when an outboard without a thermostat is started and hammered without an appropriate warm up period. The combustion chamber temperature skyrockets while the block remains cool. Pistons expand quickly and you suddenly have a stuck engine because the two surfaces are very different temperatures. The thermostat BLOCKS the flow of water through the engine so it warms up quickly. It then opens when the engine is at the open temperature of the stat. Try to run a car today without a thermostat and you will have all sorts of odd things happening from poor performance, check engine light, inoperative temperature gauge (this is way to long to describe) and possibly others. Thermostats were generally removed because the car overheated and it was easier than trying to fix the problem.

 

[Celtichawk]

Re: Thermostat Purpose

Agreed but that's why I don't buy new cars lol nah I really don't go without one I just found some laughs out of it.

It's funny how people get so defensive based of the technicality of it too. Anyways they are right don't remove your thermostat it's there for a reason.

 

[jerryjerry05]

Re: Thermostat Purpose

A thermo is needed.
A good thermo is never a reason for overheating.
Some get clogged or seized and they will be a problem.
If your overheating, the first place to look is the impeller.
The imp can loose blades and they can get clogged in the thermo.
They can also get clogged in a pressure relief system so I/Os have/had.
The risers and manifold would be next.
The block can be clogged too.
Running in shallow water and picking up a lot of sand will block the flow causing hot spots.

 

[Maclin]

Re: Thermostat Purpose

The flow rate of the cooling water is also regulated by the thermostat, water needs time to soak up the heat. In raw water cooling systems, like many (most?) boats have, the cooling water is constantly renewed and not recycled and the internals in the engine can actually overheat as the new water just slides right on by and does not have time to soak up all the heat. The temp gauge may be happy but the engine is not. In my opinion the thermostat is an integral part of this cooling system design, don't leave home without it.

 

[shep247]

Re: Thermostat Purpose

I'm no expert, and actually read this thread because I didn't know why the temperature needed to be high. Thanks for the info.

I would like to point out, however, that if the op thinks that running without a thermostat would fix an overheating problem, the thermostat probably IS the overheating problem. Maybe it's not opening when it's supposed to? Just a thought. I could be wrong though.

 

[Outsider]

Re: Thermostat Purpose

the thermostat probably IS the overheating problem.

So maybe he should replace it, and run it as designed. If it was the thermostat, problem solved. If it wasn't the thermostat, continue the elimination process without having interjected something else into the equation ...

 

[Celtichawk]

Re: Thermostat Purpose

Bulbash
So what did you find out?

 

[Bulbash]

Re: Thermostat Purpose

Ok, sorry for a late response... I found that my timing was slightly off and my water pump was not sealed properly, very minor leak. I belive that all my overheating issues came from that impeller housing that was slightly leaking. After timing got readjusted and impeller housing sealed with liquid gasket all my problems went away, boat runs great, temperature is very stable, around 180F.

One more thought... I have an extra thermostat laying around which I want to modify by drilling a small hole in it to make my engine operate lets say at 160F instead of 180F. I know there were many smart engineers designing this engines and there is a reason why they made it run at 180F, but I just want to see if running slightly cooler will help prolong engine life. What do you guys think.

 

[Boomyal]

Re: Thermostat Purpose

.....I know there were many smart engineers designing this engines and there is a reason why they made it run at 180F, but I just want to see if running slightly cooler will help prolong engine life. What do you guys think.

Don't try to reinvent the wheel Bulbash. 160? will produce the opposite effect of what you want. 160? was a compromise temperature for motors that MIGHT run in salt water. Salt tends to plate out on the engine casting above 160?. Other than that your engine will last much longer running at 180-190?. Not only that, it will be more fuel efficient.

A small hole, in any given stat, will not alter the temperature. It will allow any air, while the engine is cold and the thermostat is closed, to pass thru it quicker and let the water get to the thermostat bud so it will react quicker.

 

[Bulbash]

Re: Thermostat Purpose

Don't try to reinvent the wheel Bulbash. 160? will produce the opposite effect of what you want. 160? was a compromise temperature for motors that MIGHT run in salt water. Salt tends to plate out on the engine casting above 160?. Other than that your engine will last much longer running at 180-190?. Not only that, it will be more fuel efficient.

I think you are right.... It will not make any difference, the only thing that will change it will take longer to warm up... I think when engine runs on high rpms thermostat is always stays open atleast 1/4 or something...

 

[Boomyal]

Re: Thermostat Purpose

I think you are right.... It will not make any difference, the only thing that will change it will take longer to warm up... I think when engine runs on high rpms thermostat is always stays open atleast 1/4 or something...

engines like to warm up slowly. There are many bolted together parts which do not want rapid temperature changes. It should take about 15 minutes to go from cold to thermo opening at about 1500 rpm. Live with it. Your engine will love it.

It doesn't matter how far the thermostat is open when operatiing at warmed up temperatures. That is what it is there for to fluctuate as the situation calls for.

...and yes, an 1/8th inch hole in the thermo plate will cause it to warm up quicker but as long as you do not have any air/gas building up behind the thermostat you will once again be second guessing he engineers who designed the system.