Thermostat, Need it or not??

[RedbaranTX]

Ok, reading the recent post "1983 Evinrude 15" made me wonder if the advice I received was good or not.

I'm running a 1982 Johnson 15hp in salt water, in South TX. I was told by the local dealers that a thermostat was more of a problem that a solution down here and I would be a duffus to instal one. So, I hollowed out the Thermostat as directed and put the empty shell in instead.

Have I messed up?? Are my water temps warm enough to survive? What's worse, low temp engine or salty/sandy thermostat?

Feel free to argue it out here, I thought the other post was getting a little off track...

 

[SparkieBoat]

Re: Thermostat, Need it or not??

I would think that if your motor reaches close to normal operating temp you would be ok...may take longer to get there with out t-stat..i really haven't had much trouble with them sticking and I run in salt water, but I do run larger engines than 15 hp..I use V4 and V6s. our weather here in south GA is about the same as where you are...i have t-stats in all my motors..replace them every few years or so, never had a problem. lower operating temps will just cause higher fuel consumption and slight loss of power..maybe foul out plugs or cause higher carbon build up on rings if it runs too cold. But I am not aware of any serious damage that could occur. just my thoughts

 

[Barnacle_Bill]

Re: Thermostat, Need it or not??

Your local dealers are the dufas. Your motor will run much more efficiently with it in. The people that engineer these motors don't add a thermostat just because there is an empty hole there.

 

[rolmops]

Re: Thermostat, Need it or not??

You do not really need a thermostat, but your engine will run more efficient and will use less fuel per mile if you have one in there.It may well be that the area where you go is full of small particles and there may well be a problem with thermostat passages getting plugged up, in which case your mechanic's advice is more than just opinion. I would find out from other boaters in your area whether you are up against opinion or experience.

 

[boobie]

Re: Thermostat, Need it or not??

I'll go along with Bhile on this. Mtrs have to run at a certain temp to operate properly. Why do you think with all those lovely 4 strokes we now have start "making oil" if they run to cold? Condensation aka: Water. The 2 strokes need the same heat.

 

[HighTrim]

Re: Thermostat, Need it or not??

You should replace that thermostat ASAP, it is needed. Remember, tstats control min temperature, not max.

Without getting into mechanical theory, the t stat is needed to keep the engine running at an optimal temperature, preventing severe damage to the piston and cylinder wall.

Some motors will actually overheat. The necessary cooling water from the water pump is never quite filling the block, hence the top cylinder overheats. Some cooling systems actually rely on that t stat for a restriction, since the water is exiting quicker than it is being replenished. Removing the stat is also horrible for a water cooled rectifier/regulator.

The rings will wear out quicker (not by much, but quicker none the less), and carbon will build up.

You have to have faith in the OMC engineers as bhile stated, they get paid the big bucks, and if the bean counters could have talked them into scrapping the t stat, they would have Im sure!

Bottom line, I would replace it.

 

[RedbaranTX]

Re: Thermostat, Need it or not??

Thanks for all the opinions!

I realize now that I should have also explained that this motor is only used for pushing me to my favorite Duck Hunting spots in the muddiest bays I know of. Where it's not mud it's grass or oysters. I also run the thing very shallow, the tilt lever stays unlocked in case I hit something solid, and the last leg of the trip is usually made with the motor up on the bracket that holds it up about 30 degrees; what I call "shallow mode". I plan on a new prop every season.

I know that I'm mis-treating it, but thats what I got it for, so it's the price I pay! I do flush it and check the lower unit oil every trip. Anyway, I thought I would share that in case it makes a difference to your opinions.

As of now I think I'll probably install a new thermostat after this season.

Thanks!

 

[lovemywife]

Re: Thermostat, Need it or not??

I think I would listen to your marine shop they know the area and what they repair and for what. Based on where you go I could see it getting clogged up

 

[Cofe]

Re: Thermostat, Need it or not??

I agree with listening to your local mechanic. He knows the conditions, and what works and what don't.

Running a "gutted" thermostat is better than removing it all together. The gutted thermostat housing has a certain size hole in it to limit the amount of cooling water that passes through the head. If the thermostat is totally removed, there may not be enough back pressure on the pump to make it work right.

I have ran motors with and without thermostats. Just make sure you let it warm up for a couple of minutes before you hammer down on it. I know others will not like the idea of not running without a thermostat, but sometimes conditions will warrant.

 

[Joe Reeves]

Re: Thermostat, Need it or not??

(Thermostat Purpose)
(J. Reeves)

Many engines are considered high performance engines and demand a thermostat(s), and many smaller hp engines also require a thermostat for the following reason. The pistons actually distort/twist off round when running. The thermostat is required to keep the outer wall surrounding the steel cylinder, and the cylinder wall itself at a temperture to compensate for the distortion.

With the thermostat removed, the difference in temperture between the inside the cylinder and the water jacket quickly reaches a point whereas (in effect) you have a oblong piston running up and down a round cylinder, or vice versa. Bottom line is without the thermostat, the piston and cylinder wall could be damaged in a short period of time.

The thermostat in your car isn't there simply to have the heater function properly..... think about it.

 

[bob johnson]

Re: Thermostat, Need it or not??

Id guess, Id be looking at it in perspective...

down south in warm temps....it wont take long before a motor reaches MINIMUM temps...

then if mud and debris gets sucked up in the water pump and cloggs the Tstat opening...you ate going to get zero water!!!

one of those things...that you do something out of the ordinary because of the way it is used, but your due diligence is put to the test to watch the situation closely....

I sucked up mud and junk and it shut down my colling system....had to kill the motor...

even after taking the screen out....stuff was IN THE SYSTEM somewhere...

and I think it is still moving ariound getting stuck once in a while...

because once in a while my temps soar...I shut her down or rev her up..( bascially CHANGE the situation) and the temps start to drop fast again...and i am off , runnign good for hours maybe...

makes me watch my temps alot....i see it spike... I change... it dropps and back up i go

i think I still have some debris in the motor somewhere.

I wish there was a pressureized flush that could be attached to back flush!!!

I have even run the motor with out the tstats, hoping to move that debris out

to the OP..its your motor...take care of it, but in the end, a small motor like that isnt a big investment...

good luck

BOB

 

[OptsyEagle]

Re: Thermostat, Need it or not??

The idea that a motor without a t-stat will just take longer to get to normal operating temperature is completely false. It will never get to normal operating temperature. Once a motor reaches about 140F the T-stat starts to open. If it ever got to 150F it would be fully open, but it almost never does because the water cools it down, immediately. Think about it. What is the probability that the T-stat, fully open at 150, is the perfect opening to allow enough water to start lowering its temperature. The probability is zero. With the T-stat fully open the motor must be capable of equilibriating at a much lower temperature than 140F.

With a T-stat, the stat starts out closed. The motor heats up to 140F, then the T-stat slowing starts to open and probably an opening that coincides with about 145F is enough to start lowering the temperature again. As the temperature lowers the t-stat is slowly closing, reducing the cooling water and the temperature starts to increase, etc. etc.

This T-stat will keep your motor at about 145F plus or minus only about 5F. Without one, I would bet you would be lucky to get it to 110F maybe 115F. This is insufficient for proper operation and combustion.

Now keep in mind that a motor without a t-stat is not going to catastrophically fail. You may start fouling a spark plug now and then. You will definitely start carboning up your motor and may need a ring job, much sooner then you should.

Put in a T-stat and if you are in salt water, think about changing it more often.

 

[sasto]

Re: Thermostat, Need it or not??

My answer is yes, thermostat needed.....I run the mud, looking for seatrout, redfish, and other shallow water sportfish when in the outboard. Dirty, muddy saltwater exited my pee hole. The debris would plug up the pee hole before I plugged a thermostat. A piece of wire would clear that problem. As long as I see water exiting the cooling system, I'm not returning home.

Change often, go fishing. To me a thermostat is a small price to pay for engine security and many more hours on the water chasing the dream. Shortcuts may get you there... but paying attention to details and factory recommendations may aid in your return.

I know when the water temps around here in Fl reach 64 degrees (high for some locations)...as they are now, the boats that have no thermostat reach an operating tempurature of only 120 degrees while at low load speeds. In my book, that can't be good for an engine.

Along with most...I vote for thermostat....but.....I think you made up your mind. Whatever fits your needs.

Good Luck Fishin'

 

[Fed]

Re: Thermostat, Need it or not??

Although this doesn't strictly relate to your 15HP my outboard guy who I have total faith in explained to me that my 90HP V4 thermostats actually will start to close at high speeds do to the enormous amount of water being pushed through the engine.
No one wants to have a 'cold' motor running at 5500 RPM so this post is food for thought when it comes to removing thermostats.
FWIW my outboard guy is an old OMC trained tech.

 

[RedbaranTX]

Re: Thermostat, Need it or not??

Alright, I'm convinced. I'll put a new one in soon. I sure wish you could get to the thing without taking the whole dern head cover off...


Thanks for the advice everyone!

 

[QuackAddict84]

Re: Thermostat, Need it or not??

I am an avid duck hunter, and a huge JohnnyRude fan. But for duck hunting, you're much better off going with a surface drive engine by MudBuddy or GoDevil. They're air cooled, 4-stroke, and have a lower unit that doesn't have oil and they're impervious to mud and debris. I hunted with a 1960 18hp Johnson that always fired instantly and ran great in the low-teen temperatures, but extremely shallow water and mud are always a problem. You'd be surprised at how reasonable of a price you can pick up a used surface drive for. They're a life saver in the swamps.