I have an 87 Force 50hp. After changing the water impeller and running in a tub I noticed oil in the exhaust. I drained the lower unit and there was no water evident. Is it possible for the upper seal to be leaking? Or, could this be (the boat has been stored since last year) from last years fogging oil? The oil does smell like lower unit oil, but also similar to the fogging oil. Any help is appreciated. Thanks.