5.0Fi using oil but no smoke and no water in oil

1996 Four Winns w/ 5.0Fi Ford. It has used quite a bit of oil (quart @ day) when used for tubing and skiing for several years. It generates quite a oily sheen on the water at idle but shows no water in oil, does not smoke, and no major leaks in bilge. Still runs strong and is not run WOT. I have not done a compression check yet and I am just putting out some feelers for thoughts on this. I have owned the boat for 10 years and maintain it myself. Have not had any major repairs done to it and wondering if I should plan to rebuild it.

1. How many hours are on the engine?
2. Can you rule out, with 100% certainty an oil leak; oil pan, valve cover, oil cooler, filter etc.?
3. Pull your plugs and inspect their condition. They will give you a good indication on internal combustion conditions. Post a picture.
4. An oily sheen on the surface of the water, while at idle, is often indicative of a rich carb.
5. Execute a compression and leak down test. Post the results. These tests will point you in the direction of failing rings, valve guides etc.

Most importantly, if she still runs well, gets you out and home, I'd keep a few quarts of 30W onboard and run her. Thats my $0.02.