gearcase drain plug leak

[panasonic]

On my plug there is as the link shows a whole in the middle of the head, I can not say what it is for but I too do not think it has anything to do with venting maybe how the bolt was cast to get the magnetic end on it. That is what the OP I think is talking about.

688-45341-10-00 YAMAHA PLUG, DRAIN

Yes you are correct sir.

[TownsendsFJR1300]

On my plug there is as the link shows a whole in the middle of the head, I can not say what it is for but I too do not think it has anything to do with venting maybe how the bolt was cast to get the magnetic end on it. That is what the OP I think is talking about.

688-45341-10-00 YAMAHA PLUG, DRAIN

Agreed 100%.

[rodbolt17]

this is to funny.
3 pages on a simple leak.
why not simply pressure test the unit and fix the darn thang?????????????
it is two flat surfaces with a gasket.
aint rocket science.
that hole in the plug is simply for production line assy.
makes it fit a tool.

[fairdeal]

that hole in the plug is simply for production line assy.
makes it fit a tool.

I would love to see it.
apparently a flat-bladed driver with a 3 mm centering stud
but I've searched the 'net without a finding a trace...

[panasonic]

I would love to see it.
apparently a flat-bladed driver with a 3 mm centering stud
but I've searched the 'net without a finding a trace...

A driver tool that is in the production lathe to spin the plug blank to turn down the shank and cut the threads is what rod bolt is talking about. Other end is held by a tail stock.

The plugs in my engines are not like that..no hole in the head from manufacturing, made by a different process.

Having said that it is possible that the OP plug is leaking past the magnet and out through the center hole in head.

[Tony Sopranzi]

leaky drain plug

You got it right. Thats what I was referring to. Hey I'm no machinist or expert in anything. Just thought they had to vent the cavity the magnet gets pressed
into so the displaced air can escape. Sounds good anyway.

[DennisG01]

There's definitely no venting of the gearcase through the plug - that could end up being a way to easily let water IN. The only way oil could leak through the plug is if the hole is drilled all the way through the length of the plug/threads. Never having seen one of these, I can't say one way or the other... but how deep is the hole compared to length of the plug?

What "air being displaced" are you talking about? When you fill gearcase? Sure - but that's why the VENT plug is removed.

Does gear oil show up inside that hole? If you clean the area well, you should easily be able to figure out where the oil is seeping out from.

[ausnoelm]

I think he means to "vent" the air in the hole the magnet goes into when it is pressed into the plug, as mentioned, it is a pretty simple concept, a nice flat surface, mating to a nice flat machined surface on the plug, with a gasket/washer between them, as long as the plug screws in nice a square, and the two surfaces are OK, it cant leak, so, something is wrong, it was/is cross threaded, stripped, or damaged.

[rodbolt17]

production tooling on the assy line is a tad different than the tools we use.
while I might do 4 or 5 plugs a day the line may do hundreds.
it is a stupidly simple two flat surfaces with a gasket. one surface is damaged.

[Tony Sopranzi]

leaky drain plug

I totally agree - it is so simple but when a dealer is on the hook he's got to go
through his progression before hitting the end of the trail. I just downloaded
some pix off my I-Phone into my computer. If I can figure out how to get a couple of pix onto this site, you'll understand what led me to surmise that thre is a problem with the plug itself.

Here goes - It says I have uploaded two files.

[Tony Sopranzi]

leaky drain plug

here's a better photo

[Tony Sopranzi]

Well that didn't work. lets try again.

[boscoe99]

Yamaha has tools that defy my ability to adequately describe them.

Picture the water pump tube on an F250 with a 30" drive shaft. Lower unit is removed. A tool goes up inside the water pump tube. A drill motor turns the tool. The tube is cut from the inside out by a distance of 5 inches. Another tool then fits over the cut end of the tube. A drill motor turns that tool and rounds the end of the tube so that it will nicely slide into the water pump housing. Voila, the water pump tube is now the length that is needed for a 25" motor.

[boscoe99]

What do most hate most about flat bladed screw driver bits? They slide out of the damn slot. Can bugger up the screw or worse, adjacent structure. Or allow one to stab oneself in the hand.

Why not a bit to prevent this? So Yamamoto can install screw after screw after screw without buggering up a brand new pristine lower unit.

[pstephens46]

Well that didn't work. lets try again.

Try the new screw. Assume the dealer is paying for it. If that doesn't work, helicoil as mentioned.

Suggest the postimage for posting pics. Rodbolt can't view the format you used.
He uses an Apple II from 1977.