"My engines are Crusader 350CI
"My engines are Crusader 350CIDs and I put a separate line, with a metal ball valve "on/off' selector in each line, from the bottom of each oil pan, (used a fitting that had the same thread size as the oil pan plug) to a "Y" fitting on the inside transom in the engine room.
The single line from the "Y" goes to a 12V engine oil pump mounted on the transom.The pump has about a two foot clear line that can be put into a "dirty" oil container.
I have two electrical lines with small alligator clips on each end and when I want to change the oil from any engine it is just a matter of selecting the engine with the ball valve, and then hooking upo the electrical clips to the pump and house battery and pumping out the oil.
Been that way for about 6 years now....no problems ......however the engine oil must be hot/warm for the pump to be at the peak of its efficency."
From 600 kts to 6 kts