Draining Oil from the engine..

[ZZ13]

I was able to contort myself yesterday to look under both of my engines (350MAG). My starboard engine is original and has the drain plug right in the middle of the pan and has a hose attached to it which disappears into a maze of other stuff. I assume this is the drain tube designed to be pulled through the transom drain plug to drain the engine oil (my 175 Sport does it this way). Since I am always in the water I can't do that. But, anyone know if I reach in and grab the hose if it will freely pull toward the front of the engine? If so, then I can hook the oil sucker to the end of it to get full drainage. Unfortunately, my port engine is new and only has a plug on the center of the pan. No hose on that one. Interestingly, I could actually reach in there and wrench off the plug if I wanted to to get that last 1/4-1/2 quart out (I'd just drain that last little bit onto one of those oil absorption pads). Getting it back on in the tight quarters scares me though so I don't plan to do that.

 

[Lazy Daze]

There "should" be enough slack to get that oil hose to a point where you can get at it in at least a somewhat comfortable manner (as long as it's not wrapped around anything else). I've done this on a few boats and it's worked out on all the ones I've tried so far. You might find that it's actually easier to drop a retrieval line down the backside of the engine and pull it up that way (or to the side). The trick will be attaching the retrieval line to the plug, duct tape might work fine for that. I've done it before - just can't remember how I did it!

When I had my engine out of my current boat ('99, before that quick drain thing was standard) I added it - but that was easy since the engine was in my garage. BUT, on another boat I used to own I was JUST able to reach the drain plug (by feel only) and it wasn't too bad to remove the plug and reinstall the oil hose. Just throw a bunch of oil absorbent rags down there, along with a shallow tin foil pan (with more oil absorbent rags in it). The pan will collect most of it - just be careful pulling it out so you don't spill it.

 

[src]

Removing every last drop from the system requires that either the engine be sloped so that the drain is the lowest point, or dropping the pan. Neither of those is something you can easily arrange while the engines are in the boat, and the boat is in the water. Just not gonna happen. Even using the drain plug doesn't guarantee that the drain is the lowest point of the pan. If you want to get obsessive about it, have them put it on a hydraulic trailer and slope it however you want.

But really, unless you have seriously abused your engines, you don't need it back to "factory clean" before adding the new oil. And if you have abused them, then you need to do back-to-back oil changes with some run time between anyway.

Don't let the quest for perfection get in the way of "plenty good enough".

 

[320Bob]

General question for those of you that use a 12V oil extractor like my Jabsco. I changed oil in a boat for the very first time last Saturday and I let run for about 7-8 minutes or so until the girgling diminiished but not completely stopped. Should I be letting it run until all girgling stops? Also I think I made a mistake by not removing the oil filter first to let the oil drain back into the pan before starting the pump. I think as a result of these two things that I may have left about a 1/2 quart in there because it only took 6 qts out of a total capacity of 6.5 quarts.

 

[IanBat]

Here is a pic of how the Mercruiser 7.4L (454) dipstick tubes are mounted.

The garden hose fitting on the top of the dipstick will get the most oil out because, the fitting is the lowest part of the oil sump.
The thin tube wont do any better with this set up.

Just make sure you know what set up your dealing with to properly do an oil change.
Many boats are different.

As stated, make sure you check your setup.

I was down in my bilge today, so had a good look under my engines. As I thought, mine have standard automotive dipsticks and sumps on them. The dipstick tube enters the sump about 2/3 up from the bottom. Thus in my case the better method is the tube down the the dipstick tube.

I serviced the engines last September, ( we are just entering winter now) when I saw air bubbles coming up the tube, I jiggled the tube and got more oil.

My oil now is still clean on the dipstick and I run the boat every week minimum.

So again as said, make sure you know what your set up is


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[Gunn]

Glad this came back up; I was looking under my 2003 4.3MPI engines just last night too and thought to check where the dipstick tube routed to. While mine is slightly different than the photo above, they do route to the very bottom of the oil pan. The tube ends on side of the lower end of the oil pan.

 

[electricaldoctor]

General question for those of you that use a 12V oil extractor like my Jabsco. I changed oil in a boat for the very first time last Saturday and I let run for about 7-8 minutes or so until the girgling diminiished but not completely stopped. Should I be letting it run until all girgling stops? Also I think I made a mistake by not removing the oil filter first to let the oil drain back into the pan before starting the pump. I think as a result of these two things that I may have left about a 1/2 quart in there because it only took 6 qts out of a total capacity of 6.5 quarts.[/QUOT

Perhaps, the other 1/2 quart is in your oil filter??

 

[320Bob]

General question for those of you that use a 12V oil extractor like my Jabsco. I changed oil in a boat for the very first time last Saturday and I let run for about 7-8 minutes or so until the girgling diminiished but not completely stopped. Should I be letting it run until all girgling stops? Also I think I made a mistake by not removing the oil filter first to let the oil drain back into the pan before starting the pump. I think as a result of these two things that I may have left about a 1/2 quart in there because it only took 6 qts out of a total capacity of 6.5 quarts.[/QUOT

Perhaps, the other 1/2 quart is in your oil filter??

I'm pretty sure the oil that drained back into the pan was less than 1/2 quart but could have been as much as half that amount.(cup of coffee vs. pint of beer!:grin

 

[Lazy Daze]

Even if a dipstick tube doesn't travel externally to the bottom of the pan (like in the banjo fitting above), it's always been my experience that the regardless of where the tube enters, it continues to darn near the very bottom of the pan. I'll admit, I've never seen a dipstick tube physically enter (be attached to) the actual side of the pan as IanBat mentions - I've only ever seen them enter at the block. But everything I've ever seen with Mercruiser is that the tube extends to (basically) the bottom of the pan. Which is why using the tube as the method for oil removal has always worked. Again, I don't doubt there's stuff out there I haven't seen, but for the people on this forum with Merc's, sucking it out through the tube is fine. I know this because I'll make a note of how much oil I pull out so I know how much to put back in.

 

[Gunn]

And my thought is that if Merc puts threads on the top of their dipsticks, then it must be for good reason! I mean they wouldn't have that feature if the tube didn't go down far enough to get the oil out.

Tom

 

[Molson]

We should have Flarepoman in here to give his expertise, as its an oil thread.

 

[IanBat]

And my thought is that if Merc puts threads on the top of their dipsticks, then it must be for good reason! I mean they wouldn't have that feature if the tube didn't go down far enough to get the oil out.

Tom

Again probably right. Mine do not have threads on them.


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