I have a Mariner 115 HP outboard on a 1986 16 foot Champion bass boat. Purchased boat, with motor mounted, in June 2009. Last year and starting this year, when I first start up the outboard and travel out to the no wake buoys, it runs fine. Upon acceleration it takes off fine. However, as the day wears on and I stop to fish for a period of time (30 mins., an hour, or more) the engine gets harder and harder to start each time. Once started, I give it a little bit of throttle, up to 1100 rpm (around 4.7 mph) and then give it full throttle (hole shot) to get up and move to new fishing spot. At that moment the engine bogs down and if I don't pull back on the throttle, it will quit. It will sometimes take me 4-6 or 7 attempts but eventually it will get up and once going it runs fine. Had the motor check this spring by an experience outboard mechanic. Compressions are great (120 to 125) for each cylinder. Only 1% to 4% air pressure loss so the rings are good. In idle, the engine runs great and given throttle it does not quit. Only when in gear and needing to move does it quit when doing the hole shot as the day wears on. The mechanic cleaned the carbs, put in new spark plugs, adjusted the idle screws (1 1/4 turns out). Some where 2 or 3 turns out beforehand. I mix the oil (50:1) in the fuel tank (no fuel injection system). Advice is appreciated. Thank you.
