Lower Unit Drain Plugs

colbysmith":3eidk46f said:
As a side note, I asked my local shop how they fix stripped out holes for the oil plugs. This was in regard to the Main's engine oil drain. The mechanic said they don't have that issue, as they "suck" the oil out. I wonder if one can really get all the oil out this way? That drain plug is pretty low on the engine. Colby
Click to expand...

Colby, I have been draining my outboards thru the drain hole (do use a torque wrench, and one can find the proper size screwdriver bit for the torque wrench.

There are a number who say that can get all of the oil out--and I am going to use longer dip tubes and see if I can on my next oil change.
 
Bob, let me know how it works for you. If it's easier to do the main oil change that way, I may consider it. In the mean time, I just ordered some Helicoil insert kits for the two lower unit drain plug sizes (3/8-16 and M8-1.25) to repair those areas. Next time I change the main engine oil (probably this time next year), I'll look at the fix I did with the oversize oil plug and see how it's working. The oversize plug had a smaller 1/4" plug, which might even slow down the mess allowed by the bigger plug. At that time I can either use a Helicoil set I already have and change threads to 1.25, or pull the lower cowl and see if I should just replace the block that the oil plug goes into. Hard to see with the cowl on, but it looks like the oil plug goes into a block screwed into the engine. Suppose I could look at a parts diagram as well... Colby
 
Marco Flamingo":23f8lyzc said:
I thought about using my impact wrench with a screwdriver bit, but first I just took a big honkin' screwdriver to it and it came out easy enough. Was it the right size screwdriver? The Yamaha screw is metric (8mm x 1.25mm thread pitch). It wouldn't surprise me that the slot is also metric. I'm not sure that I've ever seen a metric screwdriver. Yamaha probably sells one just for this purpo$e.

The oil change went without incident, so I'm okay for a few hundred hours.

Mark
Click to expand...

I bought a Snap-On screw driver that fits the slot on Honda, Yamaha, Suzuki, Evinrude/Johnson/OMC & Merc 35 years ago.
That's all it gets used for, Lower unit drain plugs. No rocket surgery involved. The correct tool will last a lifetime. :wink: :beer
 
Many don't realize that there are large screwdriver bits for 1/2" socket drive in slot bits 5/8",1/2",7/16" wide and philips #2,#3,#4. They are also available in the impact wrench sets, but it is rare that an impact wrench is necessary---far better to soak the fitting with PB blaster or other penetrating oil, before putting any torque if the fitting does not move easily. We do carry a 1/2" drive impact wrench in the truck.

I carry a 3/8" drive inch lb 9" (inch lbs). torque wrench onboard the boat, and a 18" foot lb 1/2" drive. (foot lbs), torque wrench in the trailer tools in the truck. With adaptors to fit various size drives.

Conversion from foot lbs and inch lbs to Newton Meters and to meters Kilogram, are available for I OS and android devices. Not all torque specs are in ft. lbs etc.
 
When rigging aluminum sailboat masts most of the attachments are made from materials other than aluminum and they will in time experience "galvanic corrosion". A product that is widely used and very effective in preventing this degradation is "Alumalastic". It is also a non-hardening sealer and would be the perfect solution to cure leaking lower leg drain plugs.

https://burnstines.com/products/alumila ... be-25-case
 
Know this problem well, vicariously, thank God. A less than able buddy buggered the soft aluminum recess into which his drain plug fit, thinking there was a crushable washer to remove. In the end, he carved a new "seat" using an old fashioned water faucet seat repair tool, and found crushable washers to take up the slack. Ten years ago, still going.

It has to be said, however: what a gawdawful engineering decision, to emplace threads in soft aluminum in a hard to reach place. SOP in the real world would be a harder metal insert with hard threads and a hard plug so monkey wrenches could not damage them. Just sayin'!
 
I guess we could all buy e tec engines and only do lower unit once every 3 years .
On my 2016 merc 115.I have oil seeping out ever so slowly out of the drain nut that the new mercs all have . it makes changing oil very easy but it is leaking so I will pull boat change oil and see why the plug nut is leaking hopefully just a gasket .

During hurricane Irma my engine took a hit from a tree branch cracking the cowling (getting it repaired and might paint it to compliment the cd23) just wondering if it jarred something loose ?I see oil around the lower unit in the water ??
 
This last summer, after having my OB's serviced, I found an "Oil Patch" on the concrete below the stbd engine. Called the mechanic and took it back in. He was convinced it was not a leak, but replaced the gasket, refilled (which took nearly nothing) and I was on the way. Again the oil patch, on a clean paper towel this time. Same routine, and again the same, no oil required. BUT, he figured out what was going on....

When they drained the lower unit oil, some of the oil ran down into the stainless skeg protectors I have over the stock skegs. They add about 2 inches in depth, but also keep from wrecking the skegs if they drag. AND, that oil spill was gradually running down through the skeg protector and out through a small drain hole on the bottom of the protector. SO, hosed that out well with WD40 and then go use the boat. No more oil leak and lower unit is still full..

More better.

Harvey
SleepyC :moon

IMGP6689.sized.jpg
 
I second what everyone said about a large screwdriver that fills the slot.

Another thing is that the tip of the screwdriver must have sharp square edges. A screwdriver used as a prybar or can opener soon develops rounded edges on the tip.

A little work on a bench grinder can square up a rounded tip. (Careful, don't overheat the tip!)

Quality screwdrivers (Snap-on, and the like) have hardened tips to resist wear.

A screwdriver tipped socket or socket insert is also a good choice, and can can be used on a torque wrench to control tightening.

Larry H
Retired outboard mechanic
 
A hammer driven impact wrench is magic. if you can get it done with the right size screwdriver, that’s great. Corrosion sucks sometimes. The impact wrench was invented to solve this problem before mangling the screw unusable. I got a 10$ harbor freight unit, and for all I use it for it’s worth it.
 
An update. First, the slotted bit screw driver that fits is a #4 or 3/8" bit. Not only do I have that large screwdriver I mentioned earlier, but just recently also bought an impact driver set that has the right size slotted bit. Also, the helicoil repair appears to have worked. Time will tell....But the helicoils are stainless steel, so I'm hoping they seal them selves in real well due to normal galvanic adhesion. (Corrosion...) Drain screws (3/8 x 16 on the main and M8 x 1.25 on the kicker) appear to fit in well also. Next project is going to be finding some inexpensive washers for the M8 Screw. (The 3/8 are fairly easy to find...) Now that the stripped threads are repaired on the lower units, I was going to torque the screws to the proper limit so I pulled out my shop manuals and.....guess what... no torque limits listed. The Tohatsu shop manual does list 13 N-m (9 lb-ft) for an M8 bolt, but nothing specifically for the drain screw. Couldn't find anything in the Merc shop manual. So for those of you that say you are torquing them with torque wrenches, I'd be curious what settings your are using and where you found the specs? Colby
 
Wish I had the problem of striping the screw
I have an evenrude etec with aluminum lower unit
Someone over tightened the drain plug and stripped the thread in the hole
So now the hole has to be repaired
 
Colby, generally the torque is 6 to 8 foot lbs. I use a 3/8" torque wrench which reads in inch lbs, and it more compact to carry on the boat. You will still want to use a crush washer.

jkswor, I don't think anyone is is stripping the "screw"--it is the "hole"--threads which are aluminum in all of these outboard motors which is soft. The "screw" is usually Stainless steel, which is much harder than the aluminum. Solution, is to insert a Helicoil.

The below image shows how a Helicoil is inserted into your aluminum lower unit.

l-installation-process.jpg.pagespeed.ic.Q1sl9nWS8b.jpg
 
Also, regarding tapping out the stripped threads in the hole. I then used mineral spirits to flush out the lower unit of the filings. Pumped the Spirits through the vent hole, backwards from how we put the oil in, so I was not pushing the filings up thru the interior. Ran the Spirits thru until I didn't see any more filings. Then let it dry a bit before putting the oil in properly. Colby
 
I wouldn't want filings in my lower unit either. But on the flip side, those aluminum chunks are much much softer than the hardened steel gears and a stray one probably won't cause a problem. I hate this kind of stuff.....
 
When tapping for a Helicoil in a lower unit, generally there is grease put on the drill bit, (and tap) and the drill out is slow, pulling any bits of aluminum out as you go along. Same with the tap. I fund that tapping aluminum particularly, it is go forward, then back, wipe off any bits of aluminum. forward and back, etc. you can keep pushing forward with the tap I probably would run some lighter oil before putting in the 90 weight gear oil.

Some plugs have a magnet to pickup iron particles. One of the negatives with replacement screws, is that they will probably not have the magnet in the end of that screw.
 
I think that method of tapping (little at a time, backing out, then back in, works pretty well in any material. As for the magnetic screws, neither my main or my kicker came with a magnetized screw. However, you can find them aftermarket fairly easy. I still don't run one in the kicker, but I do in the Main. Colby
 
colbysmith":17kxioxd said:
I think that method of tapping (little at a time, backing out, then back in, works pretty well in any material. As for the magnetic screws, neither my main or my kicker came with a magnetized screw. However, you can find them aftermarket fairly easy. I still don't run one in the kicker, but I do in the Main. Colby
Click to expand...

That's my experience too - especially with thicker materials. The tool doesn't take long to lock up inside because of the chips and filings. I have TIG welded lower units with problems like this. I think it is best way to repair them, but lots of ways work. I've welded lots of cracks in lower units as people like to hit rocks with them.....damn rocks!
 
An O ring is a sealing rubber and seals by filling the void where it fits. Getting "hurkey" with the plug is foolish as it does not seal that way. A slight tug with a screw driver is all that is needed. If it leaks it is a bad o ring or the sealing surface is damaged.

Plugs with a crush gasket need to be tight but not o ring seals.

Jack
 
Sorry to bring this back but, I have read that helicol does not seal well and some recommend using a mercury drain plug. However I can't find how to drill and tap to that size. Anyone know what size bit and tap to use for a mercury drain plug
 
Back
Top