​Ok ... Here are the details.
I own a 2006 Honda Aquatrax F12X. It does not go above 20 mph. So far, this is what I have determined:
-- On the hose, it revs to 6500 RPM. In the water, barely 2000 RPM
-- There are no obvious cracks in any turbo hoses.
-- The solenoid that opens the air passages for the turbo does engage when the throttle is squeezed, and air passes through the mechanism.
-- The wastegate actuator arm moves freely when given a boost of air through a foot pedal bike pump. It is difficult for me to regulate the PSI, but I would guess 12 psi pushes it open, and it appears to move in and out without difficulty. I have greased it considerably and there is no rust or corrosion.
-- The small turbo impeller on the narrower side of the rubber coupler hose spins freely. This used to get bound, and I would spray it to get it to spin freely, but that is not the problem now.
-- My display is faded and I can't see if there are any error codes. However, there is no warning light on.
-- When I put in the lanyard, the warning light does not come on, nor does it beep.
-- When the ski was plugged into a Honda diagnostics computer, it showed an error code 46. However, everything with the MST tested fine.
-- When I put a boost gauge at the "T" on the side that would normally go to the actuator arm, I read 5 psi maximum whether I was on the hose or in the water on a trailer.
-- Wide open throttle on the water fails to get the actuator arm to move.
-- Jet Ski International seems to think it is the turbo that is failing to produce enough boost.
-- The guy who put it on the diagnostics computer thinks my ECM has failed.

Naturally, I don't want to start replacing parts, especially when the turbo is about $1k and the computer about the same. I will send the display to someone who refurbs the screen to make it legible for $200, but would like to know how much I have to spend getting it to work, first.

Any thoughts would be greatly appreciated. Thanks.