F50TLR Over Heating Alarm Very Tough

[Oakleyboatrepair]

09/2005 F50TLR Four stroke fuel injected Keeps setting off overheat alarm. Thus far a new impeller has been installed impeller housing gasket. Have performed a flush. Have removed all Annedroids and replaced with new none of them were broke. Have removed powerhead and water jacket cover. There was a lot of calcium but spent the time and put a lot of elbow grease into it and made sure I cleaned it to the best I could. Before reinstalling powerhead make sure all passageways could easily be blown through with air and water while plugging off other passageways. Before removal of powerhead the outlet stream was not increasing as much as it should While increasing rpms. I am basing that information off of an identical motor we have here at the shop. Just to be safe a new temp sensor was installed. Thermostat and thermostat housing have all been checked new thermostat was installed. I am completely stumped. The only thing I have not done is pull the cylinder head. Has anyone came across anything like this and have any pointers as to where to look next. I didn’t want to pull the cylinder head unless it was necessary but that may be where this is leading. And I do have the Lower Units submerged in a tank. Any help or suggestions would be greatly appreciated.

[99yam40]

if you had a lot of build up in the other passages, you can bet there is the same around the cylinder cooling passages under the head

[Oakleyboatrepair]

I’m thinking the same thing. We will know later today I will post pictures and results. Thank you for the response.

[TownsendsFJR1300]

Plus 1, ^^^.

The head is going to be MORE clogged than the cylinder liners.

Been there / done that (on a 2 stroke 200 Yammy). We accessed the liners strictly thru / with the heads off and of course the heads
.

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