Hi Tom, It's sometimes referred to as the "station wagon effect". Depending on weather conditions, the engine exhaust can roll up over the transom into the cockpit.
I know you said you don't have a bimini, but I first noticed the exhaust fumes after motoring a long time one day after installing my bimini and connector. Never noticed it before. I removed the connector and vast improvement, but still a hint of it. I checked my exhaust system and it seems fine. I haven't been able to get to the boat in months for various reasons. When I do, next steps are to:
recheck my exhaust system.
add fuel injector cleaner (maybe poor combustion).
if still noticeable install my aft weather cloths to see if that helps.
If still happening call a diesel mechanic to have the system checked out.
I know you said you don't have a bimini, but I first noticed the exhaust fumes after motoring a long time one day after installing my bimini and connector. Never noticed it before. I removed the connector and vast improvement, but still a hint of it. I checked my exhaust system and it seems fine. I haven't been able to get to the boat in months for various reasons. When I do, next steps are to:
recheck my exhaust system.
add fuel injector cleaner (maybe poor combustion).
if still noticeable install my aft weather cloths to see if that helps.
If still happening call a diesel mechanic to have the system checked out.