Regarding the oil problem, search the forum for 'oil seperator'. The two hoses running over the top back of the intake manifold to the oil seperator disinigrate and the oil seperator plugs up, so those pieces need to be replaced. And the hoses should be insulated, as the intake manifold gets cold from all the winter air going thru it.

As for towing, the X5 with factory tow hitch is rated for 5000 or 6000 pounds, depending upon configuration. That's been talked about lots too.

Post some pics with your boat hooked up to the X5!