What is the secret to getting all of the oil out of the engine? I know there is drain tube. Last year I ran the drain tube out through the Hull (boat) plug. I started the engine for a few minutes and then drained the oil into a pan.

Issues: the oil just trickled out and took about 1 1/2 hours to drain. No sure it fully drained. bow was not pointed down hill either.

Suggestions?