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Mercruiser 5.0 mpi constant alarm

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Desmond9408

New member
Hi

i have bought a second hand boat with a mercruiser 5.0 mpi v8 motor in recently. I use it mainly to pull tube or wake board behind the boat. Every now and a agian when i switch off the motor (to get the person behind the boat back into the boat) And then when i switch it back on i get a constant alarm. I have noticed that the alarm only goes on when the temp is at 200 deg. The boat shop where i bought the boat from said it is a over revving alarm but we sont rev the motor flat out. Is this a correct fault analysis? How do i solve this as it is a constant problem.
 
Hi, welcome to marineengine.com!!

Wondering how did the dealer come to a conclusion that it's simply an over revving the engine issue causing the warning horn when there appears to be a potential overheating issue if the engine temperature is truly reaching 200 degrees at any point of time.... Did he scan the fuel injected "ECM" system or just talk on the phone?

The engine temp alarm will sound at 196 degrees as you should only see right around 160 - 179 degrees as a very maximum on the dash gauge depending on many factors of boat to engine component riggings because you should have a 160 degree thermostat in the engine unless it's a closed cooling system using antifreeze which is less common to see from new.

Do you have an "Alpha" stern drive or a "Bravo" drive?
What year is the engine/boat?
Has the sea water pump impeller and/or impeller housing been changed at all/recently?
Any other known services done to the engine recently?
 
Hi

thank you for the reply.

as far as inknow the boat have a alpha drive on. It is a 2006 year model. Im not sure about any modifications or when the impeller have been changed. The dealer said they connected a computer that showed the error code for over revving




[
HTML:
QUOTE=boat_tech;568272]Hi, welcome to marineengine.com!!

Wondering how did the dealer come to a conclusion that it's simply an over revving the engine issue causing the warning horn when there appears to be a potential overheating issue if the engine temperature is truly reaching 200 degrees at any point of time.... Did he scan the fuel injected "ECM" system or just talk on the phone?

The engine temp alarm will sound at 196 degrees as you should only see right around 160 - 179 degrees as a very maximum on the dash gauge depending on many factors of boat to engine component riggings because you should have a 160 degree thermostat in the engine unless it's a closed cooling system using antifreeze which is less common to see from new.

Do you have an "Alpha" stern drive or a "Bravo" drive?
What year is the engine/boat?
Has the sea water pump impeller and/or impeller housing been changed at all/recently?
Any other known services done to the engine recently?[/QUOTE]
 
Hi

he said he connected a computer to the motor and that gave the ove revving error.

The motor is 2006 mercruiser 5.0 v8 (260hp). The. Otor have 600 hours on.

The boat hace a alpha drive. I have no idea to what modifications have been done to the motor or when the impeller have been changed
 
Change or test the stat. first, Overreving will create air bubbles in cooling system,thus running hotter than normal. Running without a stat. will cause engine to overheat also. Are the water inlets on drive blocked up?
 
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