[MaurFishin']

I apologize upfront for the length of this, but my problem is a little involved.I own a pair of 2002 F225 4 strokes with 650 Hrs on a 28Ft pursuit CC that have been dealer serviced. Used in Salt Water-boat stored on lift and engines flushed/maintained religiously. Externally engines have no signs of corrosion and look new. They run perfectly. UNTIL, I got an overheat alarm on port engine at idle only (I have temp ga's and water press ga's also). At any speed other than idle, engine cooled down to almost normal and engines ran flawlessly. After checking all obvious stuff, the dealer & yamaha diagnosed a leak in gaskets/water passages going up to the Power head (PH) that kept water from getting there at idle speeds. They pulled PH & saw corrosion/erosion in these "dry exhaust" areas starting 1/2 way down the upper exhaust guide down thru lower exhaust guide,oil pan,exhaust manifold. All these parts need to be replaced.My frustration is Yamaha's explanation of Why this happened. Yamaha says it was due to lack of maintenance (corrosion) and to prevent recurrance, the only suggestion was to use "Ring Free" I don't agree with their diagnosis.How can corrosion start at the upper exhaust guide when this is a "Dry exhaust" area? Does enging flushing reach this area? I think it may have been a coating or an assembly problem maybee even electrical leaks causing galvanic corrosion. Does anyone have experience seeing this kind of damage and what do you think could have caused it? Yamaha will not divulge this information-possiblly due to potential recall liability.Thanks alot-Maur Fishin'I have letters/pictures sent to yamaha but to no avail.

[rodbolt]

hello I have not seen such corrosion issues yet. but with salt water anything is possible. are you using the engine flusher with the engine off or flushing it the better way with the muffs? with the engine off the factory flushers on most motors cannot properly circulate water. while better than nothing its poor at best. has the water pressure control valve been serviced latly? pictures here would be nice. but so far I have not seen corrosion issues. some of my commercial engines have over 3000 hours so far.

[MaurFishin']

rodbolt, Thanks for replying!I use factory flush with engines off 15-20min each use. Pressure control valve was checked OK & replaced. (I'm new to this message Bd & not sure how to attach pictures.)Does flushing with the muffs flush the upper/lower exhaust guides area where my corrosion started? I don't understand how it would, looking at the cooling/exhaust system schematics in the service manual diagram.I would be TOTALLY satisfied with 3000 hrs & no major repairs! But having this problem after 650hrs concerns me. Yamaha is not willing to investigate this any further.Also, the compression on this engine was 185-190PSI. For a 9.9:1 ratio is this normal or high? If high, could it mean I have carbon deopsits?Thanks Again for your help!ALSO:Just so I am being totally clear, the corrosion started on the "Dry" exhaust side of these castings and progressed into the water cavity passages side. The water passages showed no signs of corrosion except where the mating surface/seal had failed from the exhaust side.I can email you pictures if you're interested.hjmessemer@teammsi.com Thanks

[MaurFishin']

RodBolt:Just so I am being totally clear, the corrosion started on the "Dry" exhaust side of these castings and progressed into the water cavity passages side. The water passages showed no signs of corrosion except where the mating surface/seal had failed from the exhaust side.I can email you pictures if you're interested.hjmessemer@teammsi.com Thanks

[Biguns]

I own a pair of 2002 Yamaha 225 four stroke outboards and had to replace both exhaust tubes they had failed due to corrosion same as yours and apparently its a manufacturers problem.