Re: tan oily goo
The tan oily goo is probably from your oil spill, once it mixes with a bit of water. As for the bogging problem, do you have the gray colored Tempo fuel lines still in the boat? If so, they deteriorate with time, especially if you have ever put any additive or ethanol into the fuel, and the insides turn to a slimey goo. This will clog your "last chance filter" buried inside your Mikuni carburetors and cause a lean out at high power. This lean condition can lead to piston seizure, so don't operate the ski at WOT until you get it fixed. Check the bottom of your fuel filter bowl. Is there a brown goo in the bottom?
The fix is to replace all the fuel lines with USCG rated hose and remove and rebuild the carbs, replacing the filter. Looks like you have a twin BN-46i carb setup. Both will have to be done. Hope this helps.