DIY oil changes

[Last Tango]

('06 22ZX, 350 Mag MPI)
I have only tried a couple oil changes on my boat by myself since I got it 3 1/2 years ago. All the other oil/filter changes were done by the dealer during annual or routine maintenance intervals. The first time I tried it myself, the oil filter was on so hard that I could not remove it with any tool. So I took it too the dealer and they struggled with it for about 30 minutes and then finally got it to budge and loosen up (what was left of it). They were the ones who installed that filter, so I got a free filter and change for my inconvenience. I am not one to repeat when once bitten, but the oil change thing is just too easy to NOT do myself. Sort of.
This weekend I tried my luck again. Fortunately, the filter came off much easier this time.
But here is the deal...

Each time I have drained the oil using the convenient Mercury Marine hose attached from the bildge drain plug to to the oil pan (factory stock item), I can only seem to drain about 3 or so quarts. I know the oil sump holds about 5 quarts. I also know that I am not going to get it all out immediately after running the boat for 45 minutes because some needs to drain back over time. I also know there is some oil in the oil filter (but only a few messy ounces since the filter is mounted high on the engine and faces downward).

So how do I get the rest out? Where is it?

The boat was on a slightly angled up work rack, I pulled the hose through the drain plug hole about 12 or so inches, and the oil came out slowly at first (I assume the oil at the end of the drain hose had to be heated up as well so once that happened it came out a little quicker). Yet, it never really pours out like when doing it on my cars.
I have removed the oil filler cap, and removed the oil filter, so there should not be any reason for it not to flow quickly and completely.

Suggestions as to why the last quart or so does not come out?

[VetteLT193]

My 6.2's hold 4.5 quarts total, with the filter. The filter holds a solid half quart. so there should be 4 left in the pan.

Just the way it's designed you can't get it all out. Figure a quart will stay down there. It's just the way it is. I think I got about 3 per side out when I did mine.

-------------------------
Ahh, forget it. I got side tracked and didn't read your whole post. On mine I'm using the dip stick method. you should get all of your oil out. but do figure a good half quart in the filter, and only 4.5 total.

[mrfixxall]

As mentioned on another post,i dislike the newer merc engines because of this reason! It seems that most of the newer merc's only hold 4 to 4.5 qts of oil if your lucky..when i do my 330 hp conversions i replace the oil pans with a 7 qt pan and toss the one that is on the engine..the newer 4.3 seem to hold 6+qts, one thing i haven't tried yer was to compare the newer style dipsticks with the older 350 mag engines(early90's)..that's where the difference may be..if the dipstick is off then the engine would take less oil.

[BUIZILLA]

if you have a bottom exit plug there is a flat washer bung weld on the inside of the pan that's about 5/16 to 3/8 thick... the oil below the bung height will never drain... and the contaminents that settle in that area will never drain either, they just accumulate until the pan is removed and cleaned completely.

[Air 22]

First is to get the oil hot before the change.
Second is to pop a hole in the filter so it drains into the pan.
Third, open oil drain hose through the bilge drain and let it go for awhile,
good time for other detail work.
Finally, sump the rest up through the dipstick with a traditional oil change pump. I normally get another quart this way.
Nothing annoys be more than black oil after a fresh change.
This seems to get most of it. All eight quarts.

Yep...what he said...:wink:

[smbarcelow]

I hook up my Mohler oil pump to the hose connected to the bottom of the pan and get about 5 1/2 quarts out of it. I'm guessing mine holds about 6 quarts. I think that the suction probably drains the oil a bit more effectively than gravity alone.

[Ghost]

if you have a bottom exit plug there is a flat washer bung weld on the inside of the pan that's about 5/16 to 3/8 thick... the oil below the bung height will never drain... and the contaminents that settle in that area will never drain either, they just accumulate until the pan is removed and cleaned completely.

Makes me wonder why there is no pan with a very slightly conical bottom to it, just enough that the residual that cannot drain is minimized. Wouldn't take much it seems to me. Anybody ever seen one done this way?

[Last Tango]

First is to get the oil hot before the change.
Second is to pop a hole in the filter so it drains into the pan.
Third, open oil drain hose through the bilge drain and let it go for awhile,
good time for other detail work.
Finally, sump the rest up through the dipstick with a traditional oil change pump. I normally get another quart this way.
Nothing annoys be more than black oil after a fresh change.
This seems to get most of it. All eight quarts.


Thanks, RT. Particularly the second step about popping a hole in the filter first before removing it.
I ran the boat, in the water, at speed, for about 40 minutes prior to the oil change. I started the oil change process within minutes of pulling it out of the water. I let the hose drain for about 40 more minutes until it was just a drop now and then. I use a funnel and an empty plastic one gallon milk jug to collect the oil. That way I can monitor how much oil has actually come out.
About 30 minutes into the draining, while the egine was still hot, I added a half quart of fresh oil to help kind of "push" out more of the bad oil.

However, from the description of the pan and the bung weld washer, it sounds like getting any more out is unlikely from simply draining. Jeez, all they had to do was put the hole at the farthest lower rear and have a just enough swale in the pan to let it all out.

[VetteLT193]

....
....pop a hole in the filter so it drains into the pan.
....

I read about this trick before my last oil change. it does not work. It seems to me it probably does work if you have a filter installed that does not have an anti-drain valve. The Merc filters have the valve, so you end up with oil coming out of both ends of the filter and even more of a mess. I did the starboard engine using the punch a hole in it method, which sucked. I did the Port engine without doing the hole and just kept a bunch of paper towels around the base of the filter and it remained pretty clean. Just have to go quick.

[VetteLT193]

I put one hole in it last time and I could tell it was staying full. So I added a second hole. pretty large. I used a Phillips screwdriver with a hammer. Waited a good 20 minutes, gave up because nothing happened, had oil coming out both ends when I finally got it off and wound up throwing the sucker overboard into the driveway to keep the mess to a minimum in the bilge.

The next one with no hole was super easy, I just did it quick. It might be a newer filter or some other anomaly. Not much came out of it though. The filters looked odd to me when they were off. I didn't use Merc this time so we'll see how next round goes. The other odd thing is the filters were really stuck on there from the factory.

The more I think about it the less I understand how putting a hole in the filter would allow it to drain if the Anti Drain valve is in tact.

[Last Tango]

With my oil filter, since it was facing down, I could foresee the problem of the oil dripping down once it was loosened, so I wrapped a raggedy old T-Shirt (from Fountain - seemed appropriate) around the base of the filter bracket, to catch any spill. I was glad it was a T-shirt and not paper towels which would have initially only deflected the oil away from the engine, but then straight into the bilge area which is far harder to access to clean.
I threw away the oil-soaked T with the filter still in it when I was done. It also gave me a vehicle for immediately wrapping the hot slippery filter and getting it out of the boat without any dripping. I did allow the filter to drain into my funnel and milk jug as part of my attempting to measure the total oil removed.