Loss of power at high altitude

[TKE381]

My Mercury 50 hp engine is running very rough at 9000 ft. I normally run it in Oklahoma at about 1000 ft. I expected the same power loss issues that you get with any gas engine, but I have lost about 50% power and it stalls often at low rpm. Additionally, it is hard to start. Any ideas? Anyone else experience this? Is it normal, or is something else wrong?

 

[Laddies]

Re: Loss of power at high altitude

At that altitude you will have to change the high speed jets as well as adjust the idle, with less oxegen you need to lean things down

 

[wilde1j]

Re: Loss of power at high altitude

You will lose ~ 30% with the motor properly jetted.