So right you are! I swapped those from one motor to the other earlier since I didnt hear the pissed off viper anymore coming from that motor. Wont even move to open. I tried to go buy a marine unit, but nobody was open or had it. So i did some further investigation and was able to find the same identical part, just not painted in automotive brand. A paint job and 2 minute install later that problem is fixed (gonna keep an extra one of these around for future).
Mercrusier part number 862998
Advance (BWD 50550)
Car Quest (734874)
The only difference was the addition of a spring inside on the shaft and the shaft went all the way to the top instead of only half way. Im sorry but I should have taken a picture.
Idle is Fixed! YEAH

OK, so in the meantime while I was running around chasing parts, my tech found the large fuse (square block with U shaped metal fuse inside) that was corroded and had been arching that was located near the trim pump motor. He said that it supplied power to all the accessories, ecu, etc.. Thinks it may be the entire problem with the high end, but would need to replace to know for sure. I had already had to replace the one on the starboard early in the season since I could not even get my trim pump motors to work. I wasn't surprised to see this one in the same condition. I think from now on when I find something bad like this I am going to automatically replace it on the other side as well.

So, until next time, maybe Wednesday I will have another update.

Thanks everyone so far for your help and hopefully I can help someone else by giving good notes on my issues.

OK, Well IAC is replaced and the main fusible link. We put it into the water and still had popping through starboard motor TB, and once it warmed up the port motor would still kick out at high RPM. Im just fed up with this issue and ready to take it to someone that can knock this problem out!

Who knows a technician that is awesome? Close to Hampton Roads? I will take a day off and tow it to you if I can get this problem fixed.... I have a Land N Sea account so parts are no issue. After the replacement of the fusible link/fuse we had a problem with the port side tach which is a new issue. So now the tach is intermittent also, I just want a master tech that I can count on for assistance or problem solving! Diagnosis shouldn't be a CRAP SHOOT........... Needing help understanding my issue ????????

I can run it still, but scared of damaging the engine with backfire and such which is most likely lean running issue (under load). I love my boat, but I am scared of enjoying it with issues . I have spent over 23K in parts and labor since Feb.

Someone please help me get this straight, I am getting to the point of being tapped out on time and money.

Anyone............................................ ...........

Check for a cracked fuel pickup in the fuel tank before you spend a bunch of money changing parts.
maybe try switching fuel lines at the tank.

Try spacing the Crank pos sensor away from the reluctor wheel apx one # 10 flat washer thickness will do.If it gets close it does wierd stuff. hf...

I will try both of your suggestions....... I will let you know how it turns out. I wish i could get my hands on a laptop with software to really see all aspects of the issues.

THANKS FOR HELP FROM EVERYONE SO FAR!!

You smoked your iac then that smoked your ECM!

Any update having same issue donzi zx 28 mercruiser 6.2 wont rev past 4000