Are t-stats considered a "preventative maintenance" replacement part?

[SweetD]

Hi Folks -

I've never replaced the t-stats on my 2005 90hp Johnson carb'd outboard. I've inspected them a couple of times when I've had tell-tale circulation issues from sucking up some crap into the water cooling system, but I've never replaced them. They have functioned fine to date and not been an issue

But it got me to wondering, are t-stats something that should be replaced every so often as preventative maintenance (like a water pump for example), or do you typically wait until one (or more) fails?

Thanks!

Dave

 

[Robbabob]

This is an excellent question!

Edit: The t-stat has a temperature stamp on it, and should be tested. Not sure of the interval for testing though. If you're talking about the boat in your signature, it should be an easy one for testing. Maybe just replace it and be confident you'll be running great.

Edit 2: This LINK , while exhaustive, comes close for my Google search. Easier to have a thermometer in a pot of water and squeeze a string into the closed thermostat. Dangle the t-stat at the same level as the thermometer bulb and being heating the water. When the thermometer gets above the t-stat setting, the t-stat should have fallen from the string. Turn off the heat and you should see the t-stat close within 10? of its temp stamp.

As stated, going through this process is probably more of a PIA than just replacing it.

Good luck!

 

[Outsider]

In salt water, I look at t-stats as 'preventive'. It's ten years old, if you're gonna take the trouble to 'test' it, just replace it. You're probably gonna have to have a new gasket anyway ...

 

[F_R]

I know I will catch heck for saying what I'm about to say, but in the case of salt water, I might relent and consider it a maintenance item. But in fresh water, I am of the opinion that 90% of them are replaced un necessarily. Besides, when they fail, they almost always fail "open". When was the last time you changed the thermostat in your car? They work on the same principle. And if you did change it, it probably was because it failed open and you couldn't get any heat out of the heater.

Just my 2c. Stop taking and call your doctor if any rash, hives, ...etc

 

[gm280]

I have to totally agree with F_R on this one. If you're not having any problems with it, why buy a new one and change it? And seriously, unless you do test the new one, how do you really know it will work? That is all different if you're in salt water. Then I see a need. But fresh water...not so fast with the changing. Same with most every vehicle. The thermostat either works of doesn't. If is not like they kind of stop working as good along the way. And they are designed to fail in the open position. Watch how they are actually made...very interesting!

 

[redneck joe]

I would change them and I've had car one fail closed. On the road, take out, continue trip. What are they a couple bucks?

 

[Scott Danforth]

Most of my t-stat failures have been closed. One had the plunger push thru the bracket, however most were wax capsule failures. I replace them every 5 years as a PM just because I no longer want to be wrenching when I should be boating or driving

 

[SweetD]

Thanks guys for the responses. I am in salt-water exclusively. If I replace both t-stats - full assemblies including springs and everything, it's looking like about $100 or so, unless I am looking in the wrong places...

 

[sumocomputers]

No Title

I had high temp problems even with good water flow, and replacing the thermostat, seat, and gasket fixed it right up. BUT I installed a brand new temp gauge when I got the engine, which alerted us to the problem. So in our case it was stuck closed, and could have killed the engine if not for the temp gauge (I still haven't tested the soundness of the factory over-temp alarm).

If you have a known working temp gauge and/or overheat alarm/sensor, you can probably just keep an eye on them. Or if you are like me, replace the things for peace of mind (and keep the old ones around as an emergency backup, assuming you have tested after removing).

Not sure exactly what engine model you have, but for the 2005 J90GLSOB, looking at the diagram I would probably get the following:

Thermostat 0435491 (#48) $24.00
Thermostat Seal 0335981 (#24) $3.50
Thermostat Cover O-Ring 0331188 (#23) $2.50

So that is about $30 each or $60 for 2.

Someone else could correct me if I am wrong, but I don't think the main outer spring usually needs replacing

If you want to replace the outer spring anyway, it is 0338174 (#49) $3.50 ($7.00 for 2)

 

[SweetD]

Thanks very much sumocomputers, very good information. I do have that same model number, often referred to as simply the "S.O.B." by me! I'm positive my overheat alarm is working, but I may just replace for peace of mind like you say...and to have the backup used t-stats on board....

 

[gm280]

While not absolutely necessary, many folks test their new thermostats before installing them just to be sure. You can do just that by placing the thermostat in a pan of water with a thermometer and see what temperature the thermostat opens up... If doesn't take long and is a sure fired way to prove a thermostat works before bolting it up. Just a suggestion...

 

[SweetD]

While not absolutely necessary, many folks test their new thermostats before installing them just to be sure. You can do just that by placing the thermostat in a pan of water with a thermometer and see what temperature the thermostat opens up... If doesn't take long and is a sure fired way to prove a thermostat works before bolting it up. Just a suggestion...

Thanks for the advice gm - sounds like an easy check to perform and worthwhile - !