Outboard VS I/O

[mawshj]

sounds to me like you are trying to fix a problem that does not or should not exist, I have an old 85 evenrude 175 rebuilt that
idles at 550 nicely, the biggest problem I have is trying to maintain steerage when running a crab line or trolling for rock.
Most service guys like to adjust the motor to 750 to 1000 rpm
and this may be needed on a 4 stroke to maintain oil pressure but does not bother a 2 stroke. if you tinker a little I think you could get your motor to run slower. Every one including the dealer told me my engine would carbon up at slow speed, but I run a crab lline at 550 all day and I have not had a problem in 20 years ?? I blow the engine out at high speed on the return to the start of the line for another pass./ But I have trolled for 6 hours at slow speed. I worry about carbon but I have not seen it.