Yes, paper clip pins A and B
Can also read codes (if any) with a resistor type LED or using a digital meter with tone mode

https://cimg8.ibsrv.net/gimg/www.off...9a6b14cbd8.jpg

Well Im guessing I found alot of my problem. Ive been reading alot of topics on the injectors in these and cleaning them should be routine maintenance, so I pulled them out lastnight and sent them to smitty. In the process found my throttle body extremely gunked up, iac and iac port where full of gunk. So cleaned throttle body out, replaced iac with new, now waiting on the injector report. Fingers crossed
https://cimg0.ibsrv.net/gimg/www.off...a7628dbbd3.jpg
https://cimg1.ibsrv.net/gimg/www.off...dc8ecf6c70.jpg
https://cimg4.ibsrv.net/gimg/www.off...66dfffe062.jpg

You should always have a scanner.

Well unfortunately my repairs didnt change anything. I had the injectors sent to smitty, cleaned the throttle body as it was nasty, replaced the iac and relearned, replaced most of the vent tubing going to intake. We did find a fitting in the upper plenum that was clogged, I believe it was the vent coming from the VST. Took the boat out yesterday and it did the same thing, wierd thing is it will run at idle all day long in gear with no surge, its always bt 900 to 1200 rpms where it will start surging. And then when I take off after putzing around for awhile it fill cough and pop for a couple of seconds before cleaning up. I might try to pull the plugs this week and see what they look like. Other wise the I have an apointment July 6 to see that they come up with.

I dont know if a faulty TPS will cause this or not, fill us in when you get it scanned

What would cause the IAC to get so gunked up?

Padraig

Crank case vapor. Happens in all motors but the 502s have a low tension oil ring on pistons from the factory so even fresh it has more blow by than Other motors. Multi port injection put injectors below the intake me and fold so none of that stuff gets naturally washed off

So, clean the IAC yearly???

Padraig

If your flame arrestor gets black easy from motor blow-by then I would move the hose away from the arrestor and place in a bottle to catch the oil vapors

I didn't have any issues with my VST 502 IAC (several years, forget how many), nor my current cool fuel 509 IAC (4 years)

Have you replaced the ignition components? Plugs, cap, rotor, wires? There's a module under the cap that was pretty ugly when I replaced all of mine.