carb jetting and timing for alt.>6000
 

My father in law has a 24' chapprell (sp) full cabin with a sbc and volvo penta duo prop. It's totally stock and i'm wondering what should be the timing for the altitude he runs it at (6000ft)? also it has a holley carb and the bowls have never been off so I don't know what the jets are but i'm sure they are stock. What should I change the jets to for the altitude? ( the carbs a little vaccum secondary.) All the numbers I got off the engine are as follows volvo penta 570 570A/ps 4100130470 868389 . the boat was set up to run here in las wages like 2000 ft altitude I only get about 4100-4200 rpm's and thats it. I don't live near the boat so I'll have to check everything in a month when I go back up there. Thanks for the insite
Rick

Keep in mind that I am no expert....

You need to look at the jets to see where you are at before you
start changing things. In the higher altitudes, there is less air
therefore he is running too rich for the conditions. Less air with
the same amount of fuel. You need to check the plugs to tune it
down a few sizes to make the air/fuel ratio goes back to its
optimum settings.

Again, you need to see where you are at with the jets and the
plugs (dark and wet or light tan).

I lost about 10mph going to Lake Tahoe (3000 - 4000ft) higher
than our normal boating areas. I didn't bother with the tuning
for a week trip.

Good luck...