‘95 Johnson 115 hp quit running and leaking oil

Help. Last week I was running down the lake, on plane, and my 115 hp Faststrike was purring like kitten. Running perfect. Then it sputtered like it wasn’t getting fuel, and eventually died. I never did get it restarted, and was stranded. As I tried to start it over and over, I noticed a lot of blue smoke. Eventually I had to use trolling motor for bout 3 miles to get back to dock and go home.
Throughout the week I searched for the problem. Pulled the plugs, which seemed ok, a lil oily, but seemed normal. After a few days, I noticed very black oil leaking from around the prop. It’s never done this before, and I’m sure it’s related to my problem. But I’m not a boat mechanic. Need some ideas what could be wrong. I’ll be taking it to a mechanic soon, as I don’t have the equipment or tools. Any simple checks I can make to diagnose this problem?
History, I did replace fuel pump last year and tested that the fuel/oil mix would alarm. I also replaced the fuel/water filter early this spring. I’ve ran the boat several times prior to this with no problems.
Its a 1995 Johnson 115 hp Faststrike, and very clean. How bad is this gonna hurt me $$?

Did you check fuel delivery from your fuel tank? You might have a fuel restriction.Maybe even do a fuel sample. You may have water in the system. Undo the fuel line from your engine. Use the primer bulb to squeeze fuel from your tank into a clear container. If it comes out cloudy . Let it sit and seperate. The black oil residue is most likely from too much oil coming from your exhaust housing. You did say there was a lot of smoke

Thank you for the quick reply. Yeah I can check the the fuel delivery. That’s simple enough. I just never thought about it since it was running so well at the time, and on plane. It was so sudden when it quit.

The black oil is probably just unburnt fuel mixture. You may have lost fire for some reason (power pack, coil, stator). You need to check for compression on each cylinder and that spark jumps a 5/8" gap with a good blue snap.

You need to do a compression test too. An engine running at speed that just dies could be a piston seizing.

Fuel delivery is definite possibility as well as a failed ignition component.

Spark test results? 7/16 minimum, all plugs out, nice fast cranking speed. Hot blue/white spark. Correct......oil/gas at exhaust is from excess. Riopka is onto your problem. Could run $300 in parts.