Thanks for the reply fellas…. We have hit it with dry gas (tried that before we discovered sea foam … may have to try that now too) and we have replaced all the plugs and wires. I believe the choke solenoid was replaced as well.
On my Thompson 240 which is a 5.7 merc, the carb had to be adjusted (re-jetted?) to troll at slow speeds. I wasn’t sure if there was an adjustment that needed be done the big block 8.1 volvo to enable slow speed trolling or if in fact it was an issue such as water in the fuel or what you had listed B-Can Man. The boat was originally set up for salmon fishing off of Lake Michigan