View Full Version : Oddest Thing

07-11-2006, 07:23 PM
This year when I was changing the oil in my 84 S & S I noticed it didn't really drain out that much oil. Upon futher inspection I found out it drained out about 3 1/4 quarts of oil. No big deal I just firgured I had burned up alot of oil last year. But when I changed the oil (5 quarts like I've put in for the last 21 years) it was way over filled and had to take out about a quart of oil to get it close on the dip stick. I put a new oil filter on and I am sure i drained all the oil out, and the boat runs great and shows oil pressure on the guages. Not 2 worried about it but wanted to see if anybody had this happen to them before and if so if it caused a problem.

07-12-2006, 10:21 AM
My 96 is quite different than your 84, but if I just drain the oil out, I only get 3+ qts out of it. Bought a $20 drill pump from Napa and connect that to the drain hose and it sucks it all out. Why it won't gravity drain all the way I don't know.

east tx skier
07-12-2006, 10:25 AM
Just to add one more experience. While my pump was occupied with the transmission fluid, I tried gravity on the oil for the first time last fall and got 5 quarts out.

07-12-2006, 10:25 AM
I always thought it had to do with the angle the motor is mounted. I have gone as far are as pulling the boat down the ramp with the bow low and changed the oil but still only got about 3.5 quarts out.

I have tried about everything short of turning the boat over to drain the oil out.

I have a brother in law who is very anal about getting every drop of oil out when he changed it on his old t-bird. He would actually leave the plug out and let it drip overnight. Then one time he went to a friend shop to do it on his lift only to find he had a second drain plug in the oil pan from the back because of a clearance hump in the pan. He had been leaving a quart behind all those years and didn't know it.

07-12-2006, 10:35 AM
If there's any resistance to air flow through the crankcase, it won't all drain out with gravity. The vacuum created by the oil leaving and the horizontal run in the hose negate the effect of gravity at some point. The oil fill cap needs to be removed and the fitting on the oil pan needs to be below the oil to get it all out.

I think I have gravity drained two boats, maybe. I drained all of the others (over 1000) with some kind of pump and don't know why so many people continue to use gravity. On a car or truck, where there is no restriction from a hose, it works well. On a boat, it takes longer than I want and I have other things to do so I prefer to speed up the process.

ski_king- Yeah, Ford has a better idea. Two drain plugs in the pan isn't one of them. I wonder how many people blew out main seals because of too much oil in the crankcase.