I have a 2000 50hp mercury outboard serial number OT062056. I do a tune up on it every year before I take it out for the first time to include spark plugs, and fuel filter. But the last two or three times ive had it out this spring it has started up with no problem and ran great in the early part of the day but as the day goes on it starts to run slower until it can not even get going over six miles per hour. I do not have a tach but it dose not sound to me as if it is getting to full rpm and as if it is under a lardge load. after a long ride home it it just wound down and stalled when at full throttle this did not occur at half or even three quarter throttle and it started right back up and idled fine. it has got me quet confused. And im just wondering if this could be one problem or many and what the problems could be?
