Somebody Explain this to me Re: T-Stats Question

[HMBJack]

I’ve owned 3 F225’s and 2 F250’s for a collective 2,300 hours of use by me personally and I have never experience a stall at idle.
No worries on a thread de-rail. I think we’re all curious.

[boscoe99]

You forgot,

3. The stalling at idle issue.

Yes, what is the stalling issue about? Have not heard of this one.

[boscoe99]

I can see a thermostat modification being desirable for some motors in some applications. A motor running in salt water that is nominally 75 degrees is going to be different from a motor running in fresh water at 40 degrees. I suspect motor designs (and maintenance plans) are structured for average use in average conditions. One size might not fit all.

[HMBJack]

Old Mako

I haven’t heard of that one. What’s the fix?

[oldmako69]

You forgot,

3. The stalling at idle issue.

[HMBJack]

The only issues with the 3.3L V6's are:

1, The Dry Exhaust Manifolds - which you can fix with your MasterCard or Visa with your Yamaha Mechanic, and
2. The Thermostat bores . This post - if you read every page - will educate you on that. Drilling holes in your T-stats is not a bad thing. You for sure get more FW flush water passing through your T-Stat bores. In my case I have decent water pressure at my slip. But to be very sure, when I can, I now flush with the muffs+ the garden hose fitting. I am very very sure I am flushing my T-Stat bores better than before.

[oldmako69]

I slapped new T Stats in my 200-hour engines last summer before this thread grew legs and hauled itself out of the swamp. Much to my dismay and severe disappointment, they were all crudded up with salt, and there is already corrosion evident in one of the thermo bores. At that time I did not know of the proclivity for the head to consume itself. So, I cleaned it all up and slapped in the new T-Stats.

Thanks for posting the photos. At some point this year, I will pull mine and drill holes as you did. I will also do what I can to the corroded bore before I button it all back up.

I do not have access to city water where I keep my boat. Well-water only, and then only for about 9-10 months of the year since freezing pipes is a problem. So when I want to use the boat in the winter months I don't have the ability to flush. And when I do flush, its at well pressure, not city water pressure. Needless to say, this salt issue is huge to me and anything, no matter how trivial that improves my odds against corrosion is a worthwhile endeavor.

[TownsendsFJR1300]

well, "everything else being equal" -
the engine with a bigger bypass in the thermostat is going to take longer to warm up
and "run colder" until it does

although "in my neck of the woods" - where "cold" means the seawater temp is just below 70F ....

Very true, ^^, but the water temp here (now), (SW Florida) is 80F and gets into the high 80's due to the shallow Gulf of Mexico, and shallow river before I get there..

Even during winter, the water temp might be 65F, my engine takes maybe takes 2 minutes to idle down from 800 to 700 (normal idle).

That vent hole is pretty small and if a slightly larger hole allows more fresh water (or ANY fresh water), to get in there, I don't have a problem with that at all..

Lastly, consider how much more water flows thru the fully OPEN thermostat vs the slightly opened hole...

[HMBJack]

Let's say you want to get maximum life out of your Yamaha four stroke, specifically the 3.3L V6.

Assuming you do all the recommended maintenance by the book - we can all mostly agree on two areas of weakness:

1. The Dry Exhaust Manifold, and
2. The Thermostat Bore

In February, I took care of #1 with my local Yamaha Mechanic. No corrosion found anywhere by the way in my pair of 2006 F250's (1,475 hours). But now I can sleep at night not thinking about that.

As to #2 - this post details everything.

I truly feel my modified T-stats (with weep holes drilled) will help minimize salt crystals & corrosion in the T-stat bore. But if you flush with only the garden hose fitting, you need to have really good water pressure. If your water pressure is less than good, or you want to be super sure you're getting FW through your T-stats, then simply flush with the muffs. I believe this practice + annual inspections will take care of any issues in the T-stat bore.

Now, because of the weep holes (vents) in my T-stats, yes - my engine will warm up to operating temperature slower. But if this was much of an issue, I should see that in my fuel economy - which I don't so far. I idle out of my harbor for a few minutes then, once in the ocean, I put the coals to my F250's to achieve cruising speed. Water temps here are at 55 degrees all year long. So, in my case, no "under heat" scenario and no side effects as far as I can tell so far.

[fairdeal]

Getting more fresh water to the other side of the stats W/O any compromise sounds like a winner to me.

Could Yamaha have done this, sure...

well, "everything else being equal" -
the engine with a bigger bypass in the thermostat is going to take longer to warm up
and "run colder" until it does

although "in my neck of the woods" - where "cold" means the seawater temp is just below 70F ....

[TownsendsFJR1300]

Getting more fresh water to the other side of the stats W/O any compromise sounds like a winner to me.

Could Yamaha have done this, sure... That engine might last another couple of years= No new engine sales

However, there is a planned lifespan for most anything nowadays.

The exhaust stack failure was a big boo boo for Yamaha.


Next time I have my thermostat out, the vent hole will get drilled...

[zenoahphobic]

HMBJack, of course you are smarter than a Yamaha engineer, they have not solved this problem. You will achieve improvement.

To be fair to Yamaha individuals their work is con*****ed by a big corporate machine that usually needs only to achieve minimum performance for least cost; they tend to make one size fits all.

You have the luxury to experiment make your one engine meet your needs. And trial and error is available to all of us whether we are engineers or not.

[BQUICK]

Here is my prototype flusher for 89 200hp. Flushes from T stats down with motor off. Replace cap after flushing and leave it dangling.

[HMBJack]

News Update:

After using my F250's for over 50 gallons since I installed my modified thermostats (see photo), I'm happy to report that ALL IS WELL!

No effect whatsoever on performance or economy (nMPG).

And I have every reason to believe my freshwater flushing is doing a MUCH better job cleaning my T-stat housings thanks to the weep holes I drilled.

I'll report back in the Fall when I pull and inspect my T-Stats and housings.

Curious if the paint I applied to the copper sides of the T-Stats minimizes the crude which develops in there by competing metals (Copper Vs. Aluminum in a wet and salty environment).

No, I don't think I'm smarter than a Yamaha Engineer - just sick of discovering a FW Flush with the current T-stats doesn't really flush or clean anything as illustrated and commented on in the above.

[zenoahphobic]

Seems I remember the automotive motors having the stats on the output of the motor before hitting the radiator for cooling.
they kept the flow down to a trickle until the motor warmed up the water in the motor enough to open the stat so water could be cooled by the radiator

Nothing wrong with your memory you indicate the direction of flow in many engines. I think the design rationale was to push the "rising" heat down through the radiator where the radiator is mounted vertically. I imagine it was thought that at slow flow rates that if the flow was from the bottom to the top in the radiator (not engine flow) that the heat dissipation is less efficient.
I guess convenient physical placement of hoses and the bonnet height had something to do with that convention, together with the "safety" of introducing cooler water to a region where the engine is not as hot first. (But it makes more efficiency sense to do this the other way around, as heat travels quicker the greater the temperature diffence between the water and metal is.
Increased cooling system pressures as cars modernised, increased the coolant temperature before it boils. The apparent need for this was to reduce the volume, and therefore the weight of, water required, and to allow the engine to run hotter to burn off more nasties in combustion ( although obviously one could easily have restricted the flow to do this).
They didn't care if car reliability was compromised. Cars now, when they overheat, do so very rapidly before detection and damage can be avoided!