I have a older 75 HP Honda 4 stroke tht is on the back of a 2' AquaPatio Pontoon. Motor has been flawless for many years. Did have to change the impeller last year. Brother had it out over the weekend and ran aground on a hidden sand bar. Said motor did overheat but he did get unstuck. Said everything fine for 2 days. This morning called to tell me would only run at WOT for a few minutes before starting to sputter and die. Would start again and do the same thing. Did take cover off and noticed oil was the color of sand. He has checked the fuel tank vent and said it was partially clogged. Will check crankcase vent and change fuel filter. Also will check oil level. Anything else should we look for? Thanks for your help!