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Somebody Explain this to me Re: T-Stats Question

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  • HMBJack
    started a topic Somebody Explain this to me Re: T-Stats Question

    Somebody Explain this to me Re: T-Stats Question

    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



    Attached Files
    Last edited by HMBJack; 03-08-2018, 04:26 PM.

  • HMBJack
    replied
    Iíve owned 3 F225ís and 2 F250ís 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 weíre all curious.

    Leave a comment:


  • boscoe99
    replied
    Originally posted by oldmako69 View Post
    You forgot,

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

    Leave a comment:


  • boscoe99
    replied
    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.

    Leave a comment:


  • HMBJack
    replied
    Old Mako

    I havenít heard of that one. Whatís the fix?

    Leave a comment:


  • oldmako69
    replied
    You forgot,

    3. The stalling at idle issue.

    Leave a comment:


  • HMBJack
    replied
    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.

    Leave a comment:


  • oldmako69
    replied
    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.

    Last edited by oldmako69; 05-11-2018, 11:21 AM.

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  • TownsendsFJR1300
    replied
    Originally posted by fairdeal View Post

    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...

    Leave a comment:


  • HMBJack
    replied
    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.
    Last edited by HMBJack; 05-11-2018, 09:50 AM.

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  • fairdeal
    replied
    Originally posted by TownsendsFJR1300 View Post
    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 ....

    Leave a comment:


  • TownsendsFJR1300
    replied
    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...

    Leave a comment:


  • zenoahphobic
    replied
    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.

    Leave a comment:


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

    Leave a comment:


  • HMBJack
    replied
    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.


    Last edited by HMBJack; 05-09-2018, 10:25 AM.

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