It works great. I've done exactly that for years. Not so much anymore as i premix now. When i had oil tank in bilge area, inevitably, some oil WAS spilled while filling tank sooner or later. I put plug in, added detergent & Mean Green & about 3" of water,( dont overload as water is 8.33 lbs per gallon. About 50 gallons willl do. Drive around, stopping fairly hard. It sloshes all the way to the front. You'd be surprised at what washes out( plastics,nuts ,washers,etc etc. & all oil,grease etc.. When you pull the plug you'll need to keep unstopping the drain from all the debris that will be coming out usually. Then it'll be clean as a whistle. Maybe two or three times if it's really bad. I like the dishwasher packets idea also.
Edited by Curtbass (08/28/17 09:03 AM)
'98 Tr20 Triton completly updated & rigged, 05 Magnum c-channeltrailer
'94 Merc 200Xri completly rebuilt & noseconed/low water pickup lower unit.