Merc 5.0 EFI running at 130 with no thermostat

[T1vande1]

Bought the boat this year. After long runs at idle it warmed up and would alarm and shut down after adding power. (Showed 170).
Changed the temp sending unit and it showed 210.
Removed the thermostat and it runs at 130. New out drive water pump. The motor has a pump attached to the engine not hoses.
Boat is a 1999, 280 hours, all freshwater.
Any ideas?

 

[CliffA]

try a new thermostat....130*F is 'WAY' to low of a temp to run an EFI engine at.....should be 170 - 180*F at least....

cliff

 

[Lazy Daze]

New out drive water pump. The motor has a pump attached to the engine not hoses.

This part is confusing. Do you have an Alpha or a Bravo drive? In other words, is your impeller a belt-driven setup or is the impeller in the outdrive?

Obviously there's an issue somewhere. Was the impeller changed AFTER the issue started? What was the condition of the old impeller? What was the condition of the impeller housing? What was the condition of the t-stat housing (you need to physically look in all the passageways for obstructions). Are the top of the elbows getting hot? Check for good flow coming to the t-stat housing. Pull elbows/risers and check passageways.