Thermostat, or not to thermostat? That is the question.

[andrewgroup]

My 1969 Runabout has a 327 V8 chevy coupled to a Mercruiser 1:1.78 Type II Outdrive. This boat has an external seawater pump. My uncle has run this boat for who knows how many years with no thermostat. Should I take the stance that what's not broke don't fix it or should I consider a thermostat. 160 degree marine....<br /><br />My other fear is not being able to get the proper gaskets, or should I use a product like form-a-gasket and skip the fiber versions....<br /><br />My uncle bought this new in 69, and I have know Idea when it went without the thermostat, I'm assuming many years ago.<br /><br />Any thoughts...<br /><br />Would this contribute to poor idle speed gas consumption?

 

[rhartSilverdale]

Re: Thermostat, or not to thermostat? That is the question.

I'm not sure about a boat engine, but I know for automotive engines running without a thermostat would create a problem for cold starts and longer warm-up time. Also, most engines run more efficiently at the manufacturer's recommended temp - because most engines are tuned for "normal" operating temperature. Running without a thermostat tends to keep the engine on the cool side. Normally, this might not be a bad thing, but running an engine cold all the time might create excess sludge and would eventualy build up and gum up its inards. Just my 2 cents worth. Good luck.

 

[merc 140 pontoon]

Re: Thermostat, or not to thermostat? That is the question.

From my Clymer manual:<br /><br />CAUTION: Do not operate the engine without a thermostat. This can lead to overheating and serious engine damage.<br /><br />Nevertheless, I ran my 1974 Merc 140 without the thermostat as a test. The engine never warmed up while idling at the dock (the temp gauge never budged from the bottom). Once I tooled around at 1500 rpm for a few minutes, the temperature rose to the usual range. Although I bought the new thermostat just last year, this year I confirmed it was the right one, and I tested it on the stove. I have found that, generally, the engine runs 5 deg warmer with the thermostat installed than with it out. I just installed a new temp gauge and sending unit (verified with hot water and candy thermometer), so I am confident about this number. But be aware that I am fighting a cooling system problem, so maybe most people will see no difference once warmed up.<br /><br />Steve

 

[loadnet]

Re: Thermostat, or not to thermostat? That is the question.

If the manufacturers put a thermostat in the engine when they produced the thing, It is in your best interest to put the correct thermostat in the engine.<br /><br />Long hard runs with NO thermostat could result in a serious overheat, thus cooking your engine.<br /><br />Bring marshmellows with you along with your bait.<br /><br />Cheers!

 

[Boomyal]

Re: Thermostat, or not to thermostat? That is the question.

I have a San Juan Heat Exchanger on my 302 0MC. Running in coolant, I use a 180 deg thermostat, which the motor likes better than 160 deg.(something about a more efficient adiabatic temperature for combustion, pistons and cylinders)<br />Last week my thermostat failed in the open position and my temperature was running between 130 deg. at fast idle and only 150 deg at cruise speed. Different motors might act differently but in my case it was coooolder without the thermo.

 

[Boatist]

Re: Thermostat, or not to thermostat? That is the question.

Andrew<br />Install the correct thermostat, 150 - 160. I will give your a few reasons. Your motor will last longer, with out a thermostat you motor will heat up at high speed then cool to near sea water temp when you slow down. Constant heating and cooling not good for the engine. Engine runs better with more power and fuel mileage at around 180, but 180 in salt water causes more deposites so normal is 150 to 160. If you run a heat exchanger and coolent in the engine then go with a 180 degree. If you ran in 130 degree plus water all the time then probably would not need one, but ocean water out here 50 to 60 degrees and insland in winter down into the 40 degree range. Oil may not get hot enough to get the normal water out. On some motors in winter the choke may not even open up. <br /><br />Bottom line if it did not need a thermostat engine builder would pocket that money and not install the thermostat.

 

[andrewgroup]

Re: Thermostat, or not to thermostat? That is the question.

My natural tendancy is to not mess with what's working. However, many of you have made valid point and I specifically think the heating and cooling aspect and the potential sludge aspect will cause me to try a thermostat in the engine. I'll take my chances on getting the right gaskets but I'll use form-a-gasket if I can't find the right one.<br /><br />As for the engine lasting longer, It's a 1969 327 V8 and I would say it's done pretty well so far. I'll post my results when I know them.

 

[andrewgroup]

Re: Thermostat, or not to thermostat? That is the question.

Oh, I forgot to mention, this engine uses and external seawater pump, JABSCO 432100001, and pumps about 30 gallons per minute through the engine at 3000RPM, it pumps about 10 gallons per minute at 800 rpm. There is no real risk of over heating an engine like this. After a hour of pulling skiers and tubers I can place my hand on any part of the engine and leave it there as long as I wish. I like the getting better fuel or operational use from the engine with the thermostat as the reason for putting in the stat...<br /><br />Thanks

 

[merc 140 pontoon]

Re: Thermostat, or not to thermostat? That is the question.

This was posted in the recent "too much oil" topic:<br /><br />

...common problem with faulty thermostat, engine runs too cool and choke never fully releases, this puts excess gas in the cylinders which wipes the oil off the rings and the extra gas blows by into the crankcase which is why it checks overfull. ... On cars that tend to be used around town on many short trips the same thing happens, then you check the oil before a long trip, it looks full and it is, but it's oil and gas, you hit the highway, the hot engine burns off the gas from the oil and the engine runs low on oil and self destructs. Moral, always have an operational thermostat.

 

[f_inscreenname]

Re: Thermostat, or not to thermostat? That is the question.

I have also fought a cooling problem that I have seemed to have won. Along the way I found out a couple of things. <br /> First; the reason the prior owner took out the thermostat was he had the cooling system hooked up wrong (something to look for). When the stat closed the raw water pump didn't have a proper by pass and it would build up too much pressure in the block blowing out freeze plugs. <br /> Second; When the thermostat closes it allows cool water to spread through out the block filling all the little nooks a cranny’s. If let open all the time the cool water pumped through block runs through it like a river as fast as it can with the path of least resistance (like a river the flow is in the middle, the water at the banks tends to sit the same thing happens in a block). In this case your temp gage will read normal but the motor, especially around the cylinder walls, will be running much hotter. In some cases the water will not even fill the whole block without a stat causing back pressure (even when its open) before running out the exhaust. This will also leave hot spots in the block, which is not good. <br /> Last like others have stated running cool, hot, cool, hot is not good. Like any car driver knows you don't just get in your car in the morning and take off. You always give it a min to warm up. If you don't run a thermostat in your boat its like starting your car in the morning and taking off without letting it warm up but doing it every time you get it hot and then it cools down to much. If your water is cool enough I can see many blown gaskets in your future or you could be lucky like a friend of mine who never runs a thermostat and never has a problem but my luck is never that good so I fixed it the way it should be so I could run a thermostat.