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Just thought I would post a heads up on this one. After starting my engine from cold start I always let it warm to operating temp (160) before dropping the hammer. Last season near fall, put it to bed time, it started giving me a check engine warning with alarm and going to limp mode. I shut it off, restarted and monitored what may be causing it, oil pressure normal, coolant temp did not exceed 162. I hauled it back to dealer 200 miles away, they told me they had found styrofoam in my exhaust manifold and although I did not exceed 165 or overtemp the engine, they said it was a differential temp alarm; one manifold was heating or sensing it was heating quicker than the other. I believe they told me if there was 5 degree difference it would trip the alarm. Big repair bill later, next season comes and same thing. Again oil pressure normal, temp 155 check engine alarm. I have discovered that it only does this on the first start of the day when cold. I have also discovered that If I heat it up quickly , like taking off at 145-150 degrees that there is no problem or alarms. I love the power and efficiency of the new gen power, but sometimes miss the simplicity of the old school.
Also discovered that when I changed my water pump impeller this past winter (genuine VP part, not aftermarket) that the supplied O-ring was not the correct one. I have been getting water in the bilge and found leakage at the impeller housing. I kept the old o-ring and saw that there was a visible difference in thickness so I swapped it out, no more leak. Since I changed it out in the off season I forgot about leak checking it come boat season, lesson learned.

Update; Hauled her back to the servicing dealer, diagnostics showed water flow is fine, has bad temp sensors on the exhaust risers. Replaced all 4 (2 per side). We'll see if that cures it.

Thanks for the update. I'll keep an eye on mine

What alarm code were you receiving (Hi Exhaust Temp?). I was receiving this running hard , above 4500. It was not a hard limp but if I kept it under 3500 it ran fine. Water temp and oil pressure were fine. Turned out one of the exhaust manifold anodes was installed backwards. The anode is cut on an angle so if it is installed backwards there is a tendency to obstruct the flow. Ran fine after that.

Stagdad wrote: Tue Mar 26, 2024 1:20 am Update; Hauled her back to the servicing dealer, diagnostics showed water flow is fine, has bad temp sensors on the exhaust risers. Replaced all 4 (2 per side). We'll see if that cures it.

Put it in the water finally, ran great temps all normal.