Somebody Explain this to me Re: T-Stats Question

[HMBJack]

Earlier this week, I put up a post titled "T-Stat Bore check - FW Flushing" because I had a good amount of salt crystal accumulation after just 14 months of use. See photo below.

I explained that I regularly flush with the engine OFF using the garden hose fitting. These are on a pair of 2006 F250TXR's.

Advice from some of you said I needed to flush with the engine ON using the muffs. For example:
" The thermostats will CERTAINLY OPEN when running on muffs and ALLOW flushing water on both sides of the stats.."

I am now of the opinion that the above is NOT at all true.
The T-stats stay locked shut and do NOT OPEN unless the internal water temps reach 158.

Here is a little experiment I performed today with my boat up on a lift:
1. Connected FW hoses to a set of muffs as well as to the garden hose fitting at the base of the powerhead.
2. Started the engine and let it idle in neutral which is about 600 RPM's.
3. With a digital heat sensing gun, during every minute of run time, I measured the temp of the starboard side T-Stat housing (outer casing where the T-stat sits inside).
4. Temperature was 74 degrees before I started the engine then it rose to 88 after 2 minutes then ranged between 90 and 98 until I shut off the engine after 20 minutes.
5. I repeated the above 4 steps on the other engine and experienced similar results. Temp range was 91 to 109 over a 17 minute run time on muffs + garden hose fitting.

When I returned home, I took a set of identical T-Stats I had removed from my F250's and placed them in a bowl of water measured at 100 degrees per a digital mouth thermometer.

None of the T-stats opened at 100 degrees. I warmed the water up to 109, my highest reading while idling, and again, none opened up - not even partially. They of course all opened when exposed to boiling water (~212).
This all makes sense since the T-stats for an F250 is set to open at 158 degrees.

So - per the above, I can conclude flushing with the engine ON with muffs does NOTHING to clean salt out of the T-stat bores.

My objective is to minimize corrosion in the T-stat bores with the premise that one needs to flush BOTH sides of the T-stat. Well, that does NOT happen in any FW flush procedure I can think of.

Please advise if you have a different view. Thanks, Jack

[boscoe99]

I can see the motor not getting hot enough to allow the thermostats to open when it is being idled. I instrumented an F150 to measure oil temperature and could never get the oil temperature up to a hundred degrees running the motor on flush muffs.

The thermostats should pass water even when they are fully closed.

What you can do is to remove the dump hoses at the bottom fittings and then see for yourself how much water is bypassing the closed thermostat. Then maybe remove the thermostat completely (simulating it being opened) and then see how much water flows out of the bottom of the dump tube.

[fairdeal]

The thermostats should pass water even when they are fully closed.

They do indeed - although I suspect because they are designed to allow a small amount of air to pass when fully closed.

What you can do is to remove the dump hoses at the bottom fittings and then see for yourself how much water is bypassing the closed thermostat.

When I did that with my F225TXRD - using a 60 PSI, 5/8" garden hose connected to the flush port -

I measured flow through the closed thermostat of 200 mLs / minute. That's about 1/2 of a gallon in 10 minutes.

[HMBJack]

Okay thanks guys. It all seems like a total waste of time though.

If in 10 minutes, you're only flushing a Half Gallon, why bother doing it at all?

It seems like a bad design by Yamaha and bad advice to promote FW flushing like there's no tomorrow.
It just doesn't "work" as evidenced by my strict maintenance program (see T-stat bore photo after 14 months above).

Two final questions -

1. Going back to muffs with engine on Vs. no muffs and only flushing with the garden hose fitting - Since very little water passes through the closed T-stat - Does it make any difference in which way to flush? i.e. With Muffs engine on? OR With the garden hose fitting and engine off?

And,

2. Can a small hole be drilled into the face of the T-Stat cover to allow more water to pass through? Like a small hole drilled in the center of the blue mark in the photo above. A half gallon in 10 minutes is terrible! Maybe a small hole will allow a whopping 2 gallons in 10 minutes... Someone could actually measure this if they want.

Justification for drilling a small hole: If the T-stat "leaks" a little, so what? The engine will still warm up to 158 degrees - it just might take a couple minutes longer - so what? At least you won't lose the engine due to T-stat bore corrosion.

[panasonic]

Try just the muffs with the engine running and measure the temp at the thermostat housings then.
I suspect that when you have both the muffs and the engine flush connected there is just to much water being forced through the engine to allow it to come up to temp with the engine at idle. The water is removing the heat faster then the engine can produce it.

A engine at idle under no load is not workin very hard. A big engine like that has a lot mass to heat up to operating temp at idle..no load.

[boscoe99]

Yamaha recommends inspection/replacement of the thermostat every year or 100 hours, whichever occurs first.

If it looks particularly grungy after that amount of time then maybe the inspection interval needs to be shortened. Try every nine months/75 hours and see what is to be seen. Adjust as necessary to fit whatever is happening with a particular motor.

Some may find they can go more than a year or 100 hours. Too many variables for a one size all inspection interval to fit everyone. Where I boated I had a several miles run up a fresh water river before I got to by storage place. My thermostats looked pristine for many years and many hours. Different salt water has diffferingg levels of salt and other minerals dissolved therein.

[HMBJack]

Panasonic - Good point. I might try flushing it on the muffs alone. I however am not confident it will reach 160 degrees but perhaps.

Boscoe - What percent of Owners of the 3.3L V6 four strokes pull their T-stats every year? Or every 5 years for that matter? I am in the very salty brine of ocean off San Francisco. Because of the pathetic design of the flush system in these engines, I agree with you that an annual clean out of the bores is necessary. Kind of like having to remove the fenders of your car to do an oil change. I know you can't throw mud at Yamaha here but I also know you know what a crappy design this is. And the flush, flush, flush message from Yamaha is a joke.

The final take away here is:

Whether you flush on muffs or the garden hose fitting - Don't think for a minute that flushing actually removes salt in your corrosion prone T-stat bores. The salt stays there and accumulates after every trip in the dead end street of your T-stat bore.

[fairdeal]

2. Can a small hole be drilled into the face of the T-Stat cover to allow more water to pass through? Like a small hole drilled in the center of the blue mark in the photo above.

I actually tried that. Must have some record of the result; I don't recall but doubt it made much difference.

[boscoe99]

Panasonic - Good point. I might try flushing it on the muffs alone. I however am not confident it will reach 160 degrees but perhaps.

Boscoe - What percent of Owners of the 3.3L V6 four strokes pull their T-stats every year? Or every 5 years for that matter? I am in the very salty brine of ocean off San Francisco. Because of the pathetic design of the flush system in these engines, I agree with you that an annual clean out of the bores is necessary. Kind of like having to remove the fenders of your car to do an oil change. I know you can't throw mud at Yamaha here but I also know you know what a crappy design this is. And the flush, flush, flush message from Yamaha is a joke.

The final take away here is:

Whether you flush on muffs or the garden hose fitting - Don't think for a minute that flushing actually removes salt in your corrosion prone T-stat bores. The salt stays there and accumulates after every trip in the dead end street of your T-stat bore.

This is a Yamaha dealer site. Separate from Yamaha the engine maker. They let us do pretty much here whatever we want to do. There are some strange filters that prevent us from typing the word goold (without the extra o) but that is about it.

We can and do throw mud at Yamaha here. I am one of their most vocal critics when it comes to their data. It stinks. All of it. I have long advocated for different designs in certain areas but Yamaha does not care what their consumers want. Give me a real electrical generation system for one. A belt driven alternator if you will.

As poor as the flushing system might be, what else can Yamaha say but to flush, flush, flush. Better to flush and maybe do a small bit of good than to not flush at all.

Now as a solution to your problem have you thought of using a horse trough filled with water into with the lower unit can be lowered? Or a flush bag? I have used same and can confirm that the water in the trough will get hot. I suspect hot enough such that the thermostats are fully opening.

Pretty good, not bad, I can't complain. Because actually, all them engine brand designs are just about the same.

[99yam40]

I would try kicking the RPM up to 1000-1200 while flushing to see if that would put enough heat to open the stats

[oldmako69]

For a bunch of supposedly very smart guys, whoever the guys were that designed, and then signed off on this cooling system weren't using their noodles. Too much Sapporo and sake perhaps?

I'm watching this thread because one of my engines already shows evidence of salt rot in the T-Stat bore, even though it only has 200 hours. So I'm guessing that my other one is on the road to hell as well. What a load of salty crap.

These engines appear to have not one, but at least three Achilles heels. Good thing they're so inexpensive.

[HMBJack]

Boscoe - You're a great resource to us. Thank you for what you do on behalf of all of us who use this site for help with our Yamahas. I, for one, greatly appreciate what you and your colleagues do for us here.

As to flushing - I cannot use a flush bucket or bag since my 33' boat is stored in a slip up high on a floating hoist (called a Hydro Hoist). I wish I could since the flush water would certainly get HOT and likely open up the T-stats.

Page 48 of my 2006 Owners Manual says "inspection/replacement" of the thermostat every 200 hours or 1 year. I see it has changed to every 100 hours now. Given the lousy flush system, this now becomes all the more important.
As stated, I truly don't believe many 3.3L V6 Owners actually pull their thermostats. Why? Because it's kinda hard relative to flushing which is easy but mostly a pointless act. Flushing looks good and makes you feel good but it's a waste of time.
You can use all the Salt Away and fresh water you want but those T-Stats will lock shut before you can say "Turn on the hose".

So instead of flushing, your time is better served pulling your T-stats as often as you can (at least annually) to keep your bores from accumulating salt. Yes, it's a bit of a pain to pull them without dropping a bolt or stripping the threads in the block. But I think it is worth doing. And doing often. And buy a few extra T-Stat housing bolts. Because you're sure to drop one or two along the way.

[panasonic]

Try just the muffs, don't turn the water on full blast, let the water pump do the work... as if the boat is tied up at the dock idling waiting to go. As Yam stated above bump the idle speed up a bit as well. I think that will work.

[HMBJack]

Yes, I will certainly switch from always flushing engine OFF on garden hose fitting to flushing with muffs and engine ON now.

I suppose even though the T-stats remain closed, jamming 90-100 degree fresh water up there with the water pump pressure can only help.

I will report back on the results of this mid year after I reach 100 hours or so.

Thanks.


Lastly and FWIW, I looked at my maintenance log, and the salt in the photo up above in my first post was after 14 months and 270 hours of use flushing only with the powerhead garden hose fitting.

[pstephens46]

FWIW, I run my motor with two hoses. F150TXRD. 65 degree tap water. I have noticed the exhaust water "pulses" between warm and cold while idling. The T stat will open momentarily and then cool down and close. Hard to imagine the F250 doesn't heat up enough to open either t stat at all.

Even still, I have found enough of a "salt bridge" from time to time to cause some pitting in the bore.