2004 and earlier F225 thermostat housing

max366

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If you have an F225 engine pre-2005, be aware that the tstat (copper) will corrode the block (aluminum) where the tstat sits. When it corrodes through, salt water is sprayed into the air intake and will trash the engine. How do I know? - my stbd engine now has a new powerhead. My port engine is somewhat corroded but I caught it in time.

Turns out that starting in 2005, Yam changed the design of the housing where you access the tstat and it included an anode, I suspect to help mitigate the problem. They now show a revised housing for the pre-2005 models, using the 2005+ part. The current exploded view for the 2004 225TXRC show the new housing with the anode- part 26 on crank 1. (The 2003 model also shows this change - I'm not sure if the 2002 and earlier show it but it's likely). The revised part # is 6P2-1240H-00-9S. I found them on ebay (used) for about $40 each- better than $75 new.

I hope this helps someone else avoid the very costly issue due to a crazy design by Yamaha. BTW, both my engines had the mid-section corrosion; another really bad design.
 

seasick

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max366 said:
If you have an F225 engine pre-2005, be aware that the tstat (copper) will corrode the block (aluminum) where the tstat sits. When it corrodes through, salt water is sprayed into the air intake and will trash the engine. How do I know? - my stbd engine now has a new powerhead. My port engine is somewhat corroded but I caught it in time.

Turns out that starting in 2005, Yam changed the design of the housing where you access the tstat and it included an anode, I suspect to help mitigate the problem. They now show a revised housing for the pre-2005 models, using the 2005+ part. The current exploded view for the 2004 225TXRC show the new housing with the anode- part 26 on crank 1. (The 2003 model also shows this change - I'm not sure if the 2002 and earlier show it but it's likely). The revised part # is 6P2-1240H-00-9S. I found them on ebay (used) for about $40 each- better than $75 new.

I hope this helps someone else avoid the very costly issue due to a crazy design by Yamaha. BTW, both my engines had the mid-section corrosion; another really bad design.
Sorry about your problems but thanks for the tip.
 

Sharkbait282

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Thank you very much for the information/education! Will be looking into this topic in the spring!

Bob.
 

Oceanbean

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Hi guys,

There is a string under General discussion on the T-stat housing corrosion issue and countermeasures.
Here is one of my posts on the subject last Feb.

I am happy to say - that when inspected for this years winterization and service (Nov 15, 2015) - both motor T-stat housings were fine. The epoxy holds up and welded in sleeve is like new.

Inspection of the T-stat and these countermeasures seem to be working.


Postby Oceanbean » Feb Tue 24, 2015 12:50 pm

Hi all, This is unfortunately another Yamaha issue. Corrosion at the T-stat housing. I have a pair of 2004 F225, 600 hrs. I was "fortunate" in that during my winterization this Nov, the shop I have do my work - knows to look for this. They probe the T-stat housing for corrosion. If the wall is permeable - they pull the powerhead and weld a sleeve in the Block of the T-stat housing. If not permeable, they apply an aluminum infused epoxy to the T-stat housing. It now becomes an annual inspection (an extra cost - because you have to pull a lot of stuff out of the way to get to the T-stats). I did the mid sections 2 years ago. I do flush after every use (engine warm) and change all the anodes. These motors are professionally serviced and maintained. Very disappointing. The motors run great. Now that I have done the mid sections, new oil pan, oil pumps, seals (the complete mid section job) due to corrosion and now the T-stat housing. I can only hope I can manage the corrosion "disease" to get a few more years out of these.

My understanding is the T-stat housing corrosion is not limited to the V6's four strokes, but has presented itself in all HP's of that genre. I suggest to all - inspect and take correction action. Maybe even pro-active application of the aluminum epoxy in the T-stat housing. What happens on the V-6's (I am only familiar with the V-6's) - if the T-stat housing is permeated, salt water blows out and gets sucked in the air intake - water in cylinders - hydraulic locked up, the motor is junk, and/or salt water is sprayed all over by the flywheel, motor soon be junk. This happened to a friend of mine this past summer.

OceanBean
2004 GW 282 F225's
Long Island, NY
 

max366

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Thanks for the link. Coincidentally, I did apply the aluminum loaded epoxy to the corroded areas on the thermostat housing last spring (after cleaning the aluminum block extremely well) and I'll report on how it's holding out after the winter. I also put it on the thermostat to isolate it from the housing since it just about touches the block. What were they thinking?!

The point I was making is that by changing the external tstat housing to the newer design that includes an anode, it should help alleviate the bad design issue.
 

Sharkbait282

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For anyone with a 2005 or older 225 or 250 four stroke, this is what the difference in the new thermostat housing on the right is compared to the old style on the left.

We bought the boat Feb 2015, and I'm going to go out on a limb and bet that we're pulling out 3-5 year old thermostats . . . I'll be opening these up annually from now on to monitor corrosion inside the housings.



I will say that the new style housing is a significantly tighter fit on at least the port side of the motors next to the intake/throttle assemblies. This isn't nearly as difficult to do as most threads make it out to be, especially after a read or two through Sim Yamaha's how-to document. And there's a yamaha part number for the little black band tie that's shown in the parts diagram . . . it's a zip tie. Just use a zip tie.

2005 and older 225 owners . . . if you don't know which you have, the new style housing has a bolt/screw on the outboard face. Old style does not.



Sorry about the big photos. Need to work on my re-sizing skills.
 

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fishin trip

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I had a 2005 225 with 165 hrs 5yrs old. I flushed my engine after every use and had it winterized and serviced every year .the thermostat got a hole in it ,salt water was sucked into the intake and shut down the engine.Yamaha said I didn't flush the engine and they had no problems with the 225 four stroke. now my dealer tells me he has seen the same thing in a few 150's.Iv'e got a 96 evinrude and never have had a problem.
 

max366

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I pulled the tstats on my stbd 2004 F225 today to see how the aluminum loaded epoxy held over the 2015 season, about 100 hrs. While the epoxy held in the corroded divot I had last year at about the 8 o'clock position, the other epoxy applied to the block flaked off when I scraped it. The epoxy was supposed to be suitable for under water but it seemed to break down.
Cleaned up the aluminum and removed the epoxy that wasn't adhered. I'm trying a thin coat of 5200 this year inside the entire tstat hole in the block. I also applied 5200 to the outside of the block tstat housing- just in case a hole forms, at least the coating should divert the water for a little while making it evident that a problem exists.
BTW I'm installing the external tstat housing with the anodes as mentioned in an earlier post. When the old housing is removed, it opens up the area making it much easier to get a the block.
We'll see how the 5200 holds up!
 

Ridenreel

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I pulled the tstats on my stbd 2004 F225 today to see how the aluminum loaded epoxy held over the 2015 season, about 100 hrs. While the epoxy held in the corroded divot I had last year at about the 8 o'clock position, the other epoxy applied to the block flaked off when I scraped it. The epoxy was supposed to be suitable for under water but it seemed to break down.
Cleaned up the aluminum and removed the epoxy that wasn't adhered. I'm trying a thin coat of 5200 this year inside the entire tstat hole in the block. I also applied 5200 to the outside of the block tstat housing- just in case a hole forms, at least the coating should divert the water for a little while making it evident that a problem exists.
BTW I'm installing the external tstat housing with the anodes as mentioned in an earlier post. When the old housing is removed, it opens up the area making it much easier to get a the block.
We'll see how the 5200 holds up!
How did the 5200 hold up for you? I’ve had the same problem and thought about trying 5200.