2006 mercury 150 2 stroke outbard rpm pulling back at crusing speed

[charger]

Hi,

my 2006 150hp 2 stroke outboard is reducing the rpm when i try to go cursing or full throttle, the audible alarm system is bypassed so I cannot see where the problem is.

The cooling looks fine and the 2 stroke tank on the engine is full.

Any ideas what the engine is protecting itself from?

 

[guyjg]

...the audible alarm system is bypassed...

Why so?

 

[charger]

alarms were bypassed by previous owner due to high cost of replacing the unit (2000$) in the middle east

 

[guyjg]

The cooling looks fine

If it has been 3 or more years replace the impeller. Inspect the thermostats and test their operation or just replace them.