So have you done this by plugging in your scan tool or reflasher ? What scan tool and can you tell me all the recalibrations you did on the 496 OEM Marine PCM 555 --

Actually I am not asking to know but telling and posting no way in the world you can do that nor I for An OEM Marine PCM 555 and ECM 555 and currently with all the MARINE OEM controllers. They are locked tunes.

Actually there is 5 people claim they can reflash PCM 555 but 3 of those 5 send them to the same place. Only people that I know can reflash PCM 555 is 2 and then OEM Mercruiser.

I have good luck with NGK TR55IX and do not touch the gap for 496 Marine engines. Had real good luck with these as well in Volvo 496's. Seemed to help at idle 4 sure as well for the Volvo's.

Now I have not bought these NGK's for the past 3 years because I buy in bulk and reorder when I run low.

Already knew this NGK makes the AC delco spark plugs for this - The NGK rep told me this years ago. Plus NGK makes a few other AC Delco spark plugs as well.

Also in the link below read my posts - ALSO like I said do not touch these gaps. You off center the double platinum tips. Its in the link from my posts below.

I Can careless what Rayler said years ago about reducing the gap to .050. - Wrong - Possible miss fires can take place.

http://www.offshoreonly.com/forums/g...s-496ho-2.html

I've never done it on those motors, but was thinking there had to be a way to do it since because I've done it on other motors. There has to be a way top adjust everything. No harm, no foul meant. I'm simply brain storming here.

I understand. I was being a tad out of line because I knew 100 percent that oh no you did not recal any ECM 555 or PCM 555 controllers no matter what software you have. Possible by not clearing that up - others might believe --- yes one can retune 555's. Just saying.

injectors
 

you should probably clean the injectors. They are very accessible and cheap to service.