Thermostat

[TXTripper]

Will running my boat without a thermostat have any harmful effects on my boat? I think it may be the source of my overheating problem when in motion, so I am thinking about pulling it. Temp is normal in neutral, heats up only when boat is moving. Does this make sense? Its an '86 Bayliner Capri, Volvo Penta Aq125

 

[Laddies]

Re: Thermostat

Most marine engines won't cool properly without the thermostat

 

[waterone1@aol.com]

Re: Thermostat

Thermostats are cheap. If you think yours is defective, replace it. The engine needs to get up to operating temp to burn impurities out of the oil among other things, hard for the engine to do without a t-stat. Your problem could also be caused by weak raw water pump, partially clogged exhaust or elbow water passages, etc.

 

[Haut Medoc]

Re: Thermostat

Don't run it without a thermostat,it will cause damage to your engine eventually.You didn't say whether your motor was FWC or raw sea water. I would suspect some sort of blockage, caused by scale resticting water flow at high RPM. Your seawater impeller could be on it's way out.J

 

[crazy charlie]

Re: Thermostat

If you mean running it ONCE to isolate the overheating source,then go for it ,but as you have already been told you might as well replace it.Removing it is harder than putting the new one in .Charlie

 

[trog100]

Re: Thermostat

"Temp is normal in neutral, heats up only when boat is moving. Does this make sense".. <br /><br />only if u have flow promlems elsewhere.. pulling the stat temporarily will find out if this is the case.. its not really a long term solution thow.. <br /><br />trog100

 

[IdahoKid]

Re: Thermostat

Umm, if you just want to find out if your thermostat is bad, pull it, have your wife leave the house (or else your gonna get dirty looks), take out a pot, boil some water, drop the thermostat in and see if it opens up. But like the others said, once it's out, you might as well replace it. You still want to test it though, because if it's working fine you still have a problem somewhere.

 

[TXTripper]

Re: Thermostat

Added info, its not the impeller going out, its brand new. Thats what I originally thought. I don't believe it to be blockage either, cause the flow is perfect when in neutral, no matter how high the RPM's are. Its annoying, its something simple I believe- because there have been instances (since the problem began) when the boat ran fine and didn't over heat for periods of time. Then just decided to go back to overheating...I don't get it. I will do the test on the Thermostat.

 

[Don S]

Re: Thermostat

Another possibility. There is a water hose connection on the drive. If it corrodes off the end inside the hose the hose sucks air when you are moving forward and you get an overheat.

 

[trog100]

Re: Thermostat

well at idle or under no load the engine dosnt generate even at higher rpm the same amount of heat as it does under load.. its not no-load rpm that generates the heat.. its the load the engine is under.. so your logic is flawed..<br /><br />personally i cant see anyway on gods earth that even a properly working stat can do anything other than restrict coolant flow.. if there is a flow promlem elswhere as a temporary measure removing the stat can only help things flow better.. i really dont see how it could possibly do any other..<br /><br />can someone clue me in as regards this "never run without a stat thing" which seesm to be a common belief.. for example why would not having a stat in place cause "localized overheating"..<br /><br />trog100

 

[tommays]

Re: Thermostat

trog even my old spitfire had a brass flow restrictor to put in place of the stat if you felt the need to remove it<br /><br /><br />tommays

 

[trog100]

Re: Thermostat

i can see the need for a flow restictor as an alternative to a stat.. assumimg the rest of the system was flowing okay.. <br /><br />but if the rest of the system wasnt working okay such as a partially clogged radiator in a car or some other kind of restriction in a boat.. would u assume the brass restriction or open stat was making the situation worse or better.. ???<br /><br />i can see why your spitfire comment might make u think some kind of restriction was needed tommays.. but to me a restriction of any kind is a restriction and if u are struggling to maintain enough coolant flow to keep an engine from running too hot any restriction brass fitting or open stat which is still a restriction is better off removed..<br /><br />a fully open stat is still a bloody great flat plate stuck right in the middle of the coolant flow.. it can only impede its progress..<br /><br />trog100

 

[bigbrownbuku]

Re: Thermostat

one of the first thing i was taught about modern cooling systems was that 80% of engine wear occurs when the engine is cold. if your engine never warms up how long do you think it will last?

 

[trog100]

Re: Thermostat

BenC.. u miss the point.. we are (or were)talking about an engine thats running too hot.. i am simply saying in such circumstances removing the stat can only improve things.. it cannot make things worse..<br /><br />as u say stats are there to make engines get hotter..they do this by restricting (in varying degrees) the flow of coolant passing thru the engine.. if u have an engine that for whatever reason is running too hot.. the last thing u need is a stat..<br /><br />and as i said before..<br /><br />"a fully open stat is still a bloody great flat plate stuck right in the middle of the coolant flow.. it can only impede its progress"..<br /><br />the other question i ask was..<br /><br />"can someone clue me in as regards this "never run without a stat thing" which seems to be a common belief.. for example why would not having a stat in place cause "localized overheating"..<br /><br />basically we are/were talking about the (possible) benefit of removing a stat with an engine thats running too hot and probably has coolant flow problems.. i think there is something to be gained from doing this.. most folks seem to think it should never be done under any circumstances..<br /><br />trog100

 

[rodbolt]

Re: Thermostat

trog<br /> on a raw water cooled motor ya need something to help slow the water down and to help maintain water pressure in the block to keep the voids filled. on an auto its pressurized by the radiator/cap assy. also in the water there is a lot of exhaust pressure on the cooling system. if ya dont belive it pull your manifold/riser seawater hoses off and start the engine in the water and see all the exhast gas blown out the water nipples. on the volvo drives there has been issues with the water outlet on top of the yoke assy and the oring between the water tube and the lower unit. its easy to find with some clear tubing. what will happen is as long as the hull is at rest its all submerged. on plane its all out of the water and sucks air. pumps are lazy, they would rather suck air than water. or you have a flow resticton in the manifold riser area.

 

[Stan's Customs]

Re: Thermostat

You are right troog...<br /><br />Boats aren't like a system which has a radiator. There the "never run without a thermostat" thinking would be correct. The circulating coolant will eventually get too hot to cool an engine if it isn't captured in the radiator with air fanned thru it lomg enough to lower its temp.....just the opposite in the winter of course. Must be held in the block long enough to allow the engine to reach optimum operating temps before the stat opens. In that instance "always" ...is proper regarding a thermostat.<br /><br />A thermostat's only purpose in a boat is to slow the coolant down and contain it in the block till it reaches optimum operating temp....Unless its alresdy too hot....then removing it completely can only help. The thermost, even if it's open restricts coolant flow to some degree, therby hampering the cooling process...So I'd chunk it til he finds out what the real problem is.. There most likely is another problem that has nothing to do with the thermostat...but removing the stat can only help till the real problem is found.<br /><br />If the stat the stat is sticking intermittently that could certainly be the only problem of course... (I am assuming above that the problem is not this elementary)...If a sticking thermostat was the case.. when completely removed the engine would run cool all the time, therby eliminating the overheating and diagnosing the problem as a sticking thermostat at the same time.<br /><br />Correcto mundo...?

 

[TXTripper]

Re: Thermostat

Ok Fella's here is the report...first off thanks for the different input. I pulled the Stat, I did the stove-top test and the stat expanded slowly- I guess it was working properly but it was a pretty slow process, is that normal? I don't worry about the engine running too cool, I am in a very warm climate, and the water will always be in the 70's...shouldn't be a problem. I have spoken with others and they seem to agree with Trog and Stan...that it can only help. Rod I have heard of that clear-tube test before...may be next if this doesn't work. I think that I am going to take it out tomorrow and test, its all put back together and I am anxious. I will let you know. I the mean time, please continue with the info, has anybody actually removed the stat for extended periods of time?? <br /> Side note for Stan, just reading your input I had a feeling you were from around here...I'm in College Station...even better, I have family in Azle!

 

[Dunaruna]

Re: Thermostat

Is it fresh or raw water cooled?<br /><br />Aldo

 

[bigbrownbuku]

Re: Thermostat

removing a thermostat to get an engine to run cool is the wrong way to appraoch an over heating problem. in the short term, great my motor stays cool. in the long term you have increased wear 3 fold. a water temp of 70f = at least 1/2 the temp a sterndrive normally should run at.

 

[trog100]

Re: Thermostat

"The circulating coolant will eventually get too hot to cool an engine if it isn't captured in the radiator with air fanned thru it lomg enough to lower its temp"<br /><br />that is the where the common "mis-belief" about not having a stat comes from stan i think.. its also wrong.. he he <br /><br />if the water flows faster thru a rad it goes round and round more often and still gets cooled at least much..probably more.. its a circuit not a one off process..<br /><br />the coolant is in the rad/heat-exchanger a shorter time but it goes thru it more times.. hence no loss of cooling..<br /><br />trog100