Jetting ballpark?

[nitrotate]

Hi everyone I'm new to the forum and new to jetboats but I have fair amount of experience with 2 strokes and understand jetting pretty well.

I recently bought a 1997 Seadoo Speedster with twin 720 motors. Single carbs with accelerator pumps. The guy I bought it from had recently replaced one of the carbs because the old carb cracked. He didn't realize it but the crack caused a lean condition from what I can tell and melted one of the pistons so I am rebuilding both engines to start from square one.

Note: I'm in Colorado at about 5300 ft elevation.

The original carb on the running motor has 170 main jet & 65 pilot
The new carb on the other motor has 167.5 main jet & 70 pilot
1.5 needle/seats
Completely cleaning carbs and rebuilding with all new internals
Initial pop off tests are right around 38 to 40PSI for both carbs Neither of them have the black springs in them.
Everything is stock including air boxes.

Here's my questions since I can't seem to find much info about the speedster specifically:

1. Ballpark jet sizes for my elevation?
2. Correct popoff psi?

Thanks in advance for any help!
Tate

 

[POPPS]

Okay,,,I have not raced at that elevation...but by applying basic "tuning"principles...the higher the elevation,,,the less oxygen,,,then the mixture of air:fuel would get richer,,,less,,,air,,,that therefore you would lower your jet sizes.,,which on cold early mornings at a race site,,,the carbs need fuel,,,the sir being cool,,,richer in oxygen,,,and that in the afternoon,,,we either re/jet to being leaner,,,or...even changing the timing curve,,,

 

[nitrotate]

Thanks for the response, yeah I'm familiar with that concept and how to adjust. I guess my problem is, I don't know what size jets these boats may have come with if you bought it at elevation or what they come with at sea level? If the came with 170 mains at sea level then I know I need to go down in size OR if this boat was always here in Colorado and someone already jetted it properly with 170's then I'll just stay there. Either way, once I get the motors back together I'll do some plug checks etc. to see where I'm at. Was just hoping to understand what these would have come with from the factory back in 1997.

 

[POPPS]

Just pull the plugs,,,they will tell you almost everything about your jetting