Oil change problems

I've just purchased a used

I've just purchased a used boat with a 4.3 EFI Mercuiser and I decided to change the oil. Because of design of the back of the boat there is very little room around the sides of the engine. I can't see or find a drain plug on the engine. The only place that oil could be drained out the pan would be where the dip stick goes into the pan and it's not possible to reach it. I did warm up the engine and pumped the oil out the dip stick tube but only got 3 quarts out before it started to suck air. Is there a drain plug out of sight or reach? I don't like the idea of leaving 2 quarts of old oil in the motor. When I added 5 quarts of new oil the dip stick showed over full.
Is this the only way to change the oil on this beast?

did you use the dipstick tube

did you use the dipstick tube or put the hose down the tube? connecting to the threaded fitting works the best

"There may be a rubber hose wi

"There may be a rubber hose with a brass plug threaded into it located on the engine. If this is the case, you pull the rubber hose through the water drain hole in the transom and then un-screw the brass plug to drain the oil."

Thanks for the advise. I'm

Thanks for the advise. I'm sure there isn't a rubber hose hanging down to drain the oil so I guess my only option is to pump the oil out. It just seems like a poor way to change oil when you leave a quart or more of dirty oil in the motor when the oil gets changed. Thanks

"3 quarts, plus .5 quart in th

"3 quarts, plus .5 quart in the filter. then if you were 1/2 quart from fully filled...that's most of it....If you change oil a couple times a year, that remaining .5 quart or so will be a non issue."

Remove the oil fill cap when s

Remove the oil fill cap when siphoning oil from the pan. Oil should be at operating temp.