Thermostat Question

[tomelenbaas]

I was servicing my boat ('88 Mariah - Ford small block) and discovered there is currently no thermostat installed. I have no idea when or by whom it was removed, but it has to be at least 4 years ago since I've been doing all the routine maintenance for the past several years. I generally run the boat in warmer waters (70 degrees plus) and have noticed no problems associated with the missing thermostat. How essential is it?

BTW - the only cooling issue I notice is that when the engine is shut off it heats up to about 200 degrees, but immediately cools down once the engine is started. The normal operating temperature is 160 degrees.

Thanks.

[wotan2525]

I was servicing my boat ('88 Mariah - Ford small block) and discovered there is currently no thermostat installed. I have no idea when or by whom it was removed, but it has to be at least 4 years ago since I've been doing all the routine maintenance for the past several years. I generally run the boat in warmer waters (70 degrees plus) and have noticed no problems associated with the missing thermostat. How essential is it?

BTW - the only cooling issue I notice is that when the engine is shut off it heats up to about 200 degrees, but immediately cools down once the engine is started. The normal operating temperature is 160 degrees.

Thanks.


I'm stumped as to how your engine gets up to 160F without any thermostat in it. I usually run my boat in similar water temps and until this year ran without a thermostat -- the temp never got above the 100 degrees at the bottom of the gauge. It was honestly just easier to run without a thermostat because I didn't have a heater and it made it very easy to tell when I had an impeller problem. This year I became paranoid about "sludge" so I put in a thermostat.... I know that I should be getting better fuel economy but I don't track it that much so I have no idea and I know that even with no thermostat, the oil was still getting up to temp.

[jaywidhalm]

Running without a thermostat should not hurt anything. Without a thermostat there is nothing restricting water flow, so your engine will run cooler (usually around 100 degrees or so). I am also not sure of how you are hitting 160 without one in at all. When my old one was stuck all the way open I was lucky to hit 120 degrees. You should definately not overheat without one in, and running cooler will just rob a little bit of power. If it is running at 160 with no thermostat, you may want to check your impeller. You may be getting little water flow from a worn one. Hope this helps, Jason

[tomelenbaas]

Thanks for the input. The impeller is replaced yearly but I have had situations in the past where the impeller did break apart. Could a piece of an old impeller be partially blocking the water lines and causing the engine to run hot? If so, where is the most likely place to look.

Thanks.

[jaywidhalm]

I suppose there could be a piece somewhere blocking flow, anything is possible with a boat!! I am not sure if there is a best place to look for it though. It doesn't sound like you are running hot though, so I probably would just run as is. Just keep an eye on your temp gauge. Stay below 170 or so.

[NeilMcg]

Another key symptom is change in exhaust sound. Does it sound louder than normal? Also a few initial pumps of the throttle in neutral should tell you.

[szarik5]

If you have a restriction causing the temp to go up to 160 degrees, there will be a substantial change in engine temperatures at different power settings. If it stays at 160 I would look at the pums or more likely your indicator.

I did have an impeller disintegrate in my 92 ts6m comp and the engine would overheat at full speed. I found pieces near the impeller partially blocking coolant.

Newer engines need a specific engine temperature for proper computer controll. As long as the engine has not been upgraded, it will for the most part do fine running at lower temperatures - still not recomended long term for lubrication and combustion.

Good luck

[86Pirata454]

Not sure if its like a car, but without a thermostat a car will overheat because the coolant/water flows too fast withou absorbing the heat or transfering it to other parts. Is this the opposite on boats because you arent reusing the coolant/water?

[NeilMcg]

A car will overheat because it needs to dissipate the heat while in the radiator. The boat system, as you know gets a continual stream of cool lake water so there's no danger of it overheating.

[csuggs]

I thought that when a car was hot (or operating temp was above the thermostat rating) the thermostat would open and stay open until the temp dropped below the thermostat rating. So why would a car overheat without a thermostat? Would it not be the same with an open thermostat as with no thermostat?

[michael hunter]

I have heard that cars will overheat without a Tstat because the coolant flows too fast through the radiator to cool off. This may have been true in old cars. I have never seen it in newer cars. The purpose of the Tstat is to control engine temp for maximum efficiency.
Too cold will cause poor fuel economy and create sludge.

[86Pirata454]

I thought that when a car was hot (or operating temp was above the thermostat rating) the thermostat would open and stay open until the temp dropped below the thermostat rating. So why would a car overheat without a thermostat? Would it not be the same with an open thermostat as with no thermostat?
There is still a large restriction so the coolant doesnt rush through the engine and not absorb any heat and rush through the radiator and not give any heat off. Many companys make restrictors to prevent this.


I have heard that cars will overheat without a Tstat because the coolant flows too fast through the radiator to cool off. This may have been true in old cars. I have never seen it in newer cars. The purpose of the Tstat is to control engine temp for maximum efficiency.
Too cold will cause poor fuel economy and create sludge.
Its more the people who think it will make their car faster or the not so smart ones. For example, i helped my friend build his turbo mustang, he didnt spare a dime on this car, but he didnt research anything before he bought it. The thermostat housing he bought doesnt work with a therm, it needs a special restrictor that he is too cheap to buy. so anytime we go out his car overheats about half way to where we are going haha

[michael hunter]

Once you start adding go fast parts you can throw out all the rules. I never got involved in race cars only stock. It always amazes me how the average guy thinks he can put a bunch of parts on and do better than the engineers that designed it. The simple fact is for every action there is a reaction. When you change things you will cause problems when you cure those problems you will cause other problems. If you get them all fixed you will have a very fast short lived engine with poor reliability. Look at professional racing they have a unlimited budget and most cant finish the race.

[NeilMcg]

You're right, the thermostat does exactly that. However, even with the thermostat open, it still moderates the fluid flow to a point where it has time for proper heat exchange in both the water jacket (absorbtion) and the radiator (dissipation). This doesn't apply to a boat because there is only one point of heat exchange. The real danger comes as a result of turning off and then restarting a warmed up engine while running in frigid water. The sudden surge of cold water water can damage the engine.

[csuggs]

You're right, the thermostat does exactly that. However, even with the thermostat open, it still moderates the fluid flow to a point where it has time for proper heat exchange in both the water jacket (absorbtion) and the radiator (dissipation). This doesn't apply to a boat because there is only one point of heat exchange. The real danger comes as a result of turning off and then restarting a warmed up engine while running in frigid water. The sudden surge of cold water water can damage the engine.

Good point about the fridgid water. Maybe it would be best to leave the boat running when the water is below a certain temp . . .

[jet]

I can't remember if mine is pulled out or not, I think Its out right now. I never got mine to run cool with a thermo in it. I even went down to a 140 degree but every time you cut it off it would climb to 200-220, I know Its kind of a false reading in the thermo housing area but It scared the hell out of me all of the time. Now saying all of this if you don't have a thermo in YOU NEED TO CHANGE THE OIL YOUR USING. I use a cold weight oil 5w-something synthetic and let the engine warm up pretty good to heat up the oil. Jet