Ihave a 1984 80 hp exaust thru hub merc .Ijust got it and have ran it in tank quiet a few times.Is it normal for these motors to put out a good bit of oily residue.
I have a 50HP Johnson with exhaust through hub. I always winterize it in late fall by cleaning it with engine tuner and then using fogging oil to store for winter. When I fire it up in the spring there is always a heavy residue from the exhaust. Also if your oil gas mixture has too much oil you may have this problem. Does it smoke more than normal?
If it is a really heavy sheen you might have a leaky fuel pump diaphram that is not causing any problems or maybe a check valve in the recirc system on the bottom cylinder maybe malfunctioning--longshot.
