Don't be lazy with your oil changes!
Don't think that your boat doesn't need an oil change based on what see on your dipstick!
During my pre-season prep on my newly acquired 2005 Maxum 1800 SR3, I noticed something disturbing and wanted to pass it along to you guys. The prior owner must have thought this even though he told me he changed the oil every season. When I looked at the dipstick it looked really clean but when I drained it (the proper way) the colour shocked me. It was "dark black" (very dirty) and couldn't have been changed in years. It was so sad to see as the engine was recently rebuilt and only had 105 hours on it. I realized why.
The dipstick on this particular year engine (2005 4.3L) and possibly many more models, doesn't feed through the engine block and dip into the oil from above. Instead the tube runs down the side of the engine to a "T" fitting attached to the drain on the oil pan. That's fine for checking the oil level, but because of this, oil in the oil pan never really mixes with the oil in the tube and doesn't change color or represent the actual condition of the oil.
It also won't show signs of water in the oil. How ridiculous is that? Especially on a boat engine!