2011 seadoo boat 150 speedster surging up and down on full throutle but idles fine in neutral and changed the plugs and new gas and tps sensor and still no differnce

SOURCE: I have a 1994 ford

I've been trying to get the timing procedures for this model, as I have a 94 aspire. sounds like you have something (a timing light) hooked up and can see the the timing mark moving, but I assume when you say you've shorted st1 to ground, that eliminates the computer control of idle. So the the computer is out of the equation, right? Or is it not electronic ignition?
I have eliminated some idle roughness by cleaning and setting spark plug gap, new air filter, and if its time, a new gas filter. Then, cleaned the sensors inside the air filter compartment, and the intake manifold. I'd heard of using wd40 on the same part of a taurus referred to as a oxygen sensor. But eventually, cleaning the plate that opens to let oxygen into the intake manifold is a good idea. I have 160,000 miles on my aspire ( 4 door hatchback 5-speed manual) and it gets 49 mpg on trips. I replaced the gear oil with mercon dextron last winter, It may have helped increase a few mpg. Also, check for vaccum leaks in your vaccum hoses. that's all I can think of right now.

SOURCE: Idles bad

Sounds like you may have an upper intake manifold leak. Typically the gasket between the Plenum and the lower intake dries up and gets sucked into the intake a little causing a leak and a high idle issue. The repair requires the removal of the plenum and replacement of the gasket. NOTE: there is a torx bolt hidden between the center plenum runners and can only be seen by looking straight down at the top of the plenum and it may be covered in dirt. If you have to use a bar to pry off the plenum you probably have missed a bolt. Typically it is the one noted above. Best of luck.

SOURCE: rpm shoots up to 3500 dwn to 1500 up again down again .

scan it check tps sensor.also check for sticking throttle linkage.also check idle speed control.

SOURCE: Idle up/down in park/neutral Gas smell exhaust dies on turns

Check your PCV valve and Map Sensors.

SOURCE: 1998 Ford F-150 4.2 V6 starts and idles fine ibut bogs when step

i had a van do this same thing to a tee turned out to be a broken key pin in the harmonic balencer causing the timing to ****** replaced balencer and ran like a dream there is a crank sensor grid on the balencer when the key pin broke it trew the timing off