gearcase drain plug leak

[Tony Sopranzi]

Hi,
I have a 2010 Yamaha 25hp motor. I recently had the dealer do a gearcase
service. The motor came back leaking lube at the drain plug. The dealer replaced the red washer on the plug with a black washer which he said was an improved product. We talked about the possibility of an old washer still in the
case or damaged threads or gasket seat. Within a few hours after arriving at home, the case was still leaking. I returned to the dealer and asked that the
cause of the leak be identified before doing anything else. One day and a half
later they called to say they used an "O" ring and in that day and a half there was no leaking. When I picked the boat up I fingered the drain plug screw head and there was oil residue on it. The attending employee opined perhaps it was residual. A possibility I thought. Upon arriving home I cleaned the plug with solvent until it was clean. the following morning there was a puddle of lube under the skeg and the plug and skeg wree wet . Any ideas as to the cause? The dealer has been very accommodating but I'm afraid that something untoward may have occurred during the gear case service. Thank you in advance for your professional opinion.
Tony

[pstephens46]

There was a guy who reversed the two plugs recently. Put the drain screw in the vent hole and vent screw in drain. Hard to imagine a service center doing this. Is it possible they grabbed a screw from another motor by mistake? If that is not the case, something is damaged. The old gasket worked pretty good, the new one should be even better. I would take the screws out and inspect them and the seating areas.

[DennisG01]

This one shouldn't be rocket science. Either the male or female threads are buggered up and the plug is, for lack of a better word, wobbling in the gearcase such that it doesn't stay tight and loosens up from vibration, or there's an issue with the sealing/mating surface.

Have you tried tightening the plug? Does it tighten or "rock" a bit?

The plugs should have the same threads and sealing surface so swapping plugs "shouldn't" cause this effect. But I say that without ever even seeing the model engine in question - only saying this from every other gearcase I've ever seen.

Are you positive that the leak is coming from the drain plug and not the vent plug?

[panasonic]

Take it back to the dealer and tell them not to call you until it is fixed properly and not leaking a speck. When you pick it up ask them for the exact details of the repair on paper. I fear they buggered the threads on the case and would think they would have already replaced the plug if it had bad threads.

But fooling with it yourself at this point it may give them the excuse that you somehow had something to do with it.

My two cents.

[rodbolt17]

unless they stripped the thread and it wont tighten it is not a thread issue.
I have seen the sealing surface on the plug damaged by a hand impact.

[TownsendsFJR1300]

Plz post your model #.

There is a FLAT, GASKET that goes in with the drain bolt, NOT an O-RING.

With the top screw still installed, you can remove the lower drain bolt, install the proper flat GASKET and re-install. Good and snug.

Re-check after a days outing..






.

[pstephens46]

There is a new gasket/oring. Don't know for how many models but assume the flat red gasket was creating issues. The screw becoming loose was the issue I noticed. The update bulletin was posted on another forum.

[TownsendsFJR1300]

There is a new gasket/oring. Don't know for how many models but assume the flat red gasket was creating issues. The screw becoming loose was the issue I noticed. The update bulletin was posted on another forum.

Apparently the new and improved ISN'T so improved...(No mention of leaks previous to this service)

Just like the new and improved mushroom poppit valve...

[pstephens46]

Found it

https://www.bandofboaters.com/forum/...unit-vent-plug

[TownsendsFJR1300]

Found it

https://www.bandofboaters.com/forum/...unit-vent-plug

Interesting...

Sounds like the gasket probably wasn't lubed (as mentioned in
that snippet) and probably bound up, ripped, etc.

It'll have to come off and inspected and / or replaced at this point.

It also mentions ALL new drain gaskets will be this...


.

[dray0151]

Last time I ordered and got the gaskets I got the new black ones. Just assumed it was again new and improved, but no note of any type about different process to install. Since my new ones did not leak I must have has a bit of oil on them which I usually will do with a gasket and just screwed in snug no torque wrench to use on a screw like this.

[Tony Sopranzi]

leaky gearcase drain plug

et al,
Thank you for your input. The model is: F25LA ser. 6BPk 1005486

The flat red gasket was not creating any issues. There was no leak with the red gasket installed. The leak occurred after the lube was drained/replaced. The tech may not have replaced the old red gasket with a new one.

The red gasket was replaced with a flat black gasket then the "O" ring.

The boat won't go near the water until the leak is corrected.

The leak is definitely not at the vent plug but rather at the drain plug.
also not coming through the rear prop shaft seal.

The dealer has yet to articulate what the cause is - they're just changing
out gaskets. I do know they did not have a new drain plug in stock. They may have ordered one when they put in the "O" ring.

I hadn't considered that the tech may have tried to put the vent plug in the drain hole - its possible. Its also possible the tech cross threaded the threads. When I took it back the first time, a different tech did the replacement and when he hand threaded the drain plug in he said it stopped,
feeling like there was a burr or something in there but eventually he was able to screw it down to the seat against the gasket. That may have exacerbated
the problem.

If the threads are damaged, and if they tried "chasing" them before they
put in the "O" ring and it didn't stop the leak, perhaps it may require going to
a larger drain plug from a larger gear case (if they make larger plugs) and re-tap the hole for the larger plug If there is enough room up there to take a larger plug.

What a mess. All because I was too lazy to do it myself. Will know more
tomorrow when I inform the dealer he hasn't treated the cause of the leak yet.

[TownsendsFJR1300]

et al,
Thank you for your input. The model is: F25LA ser. 6BPk 1005486

The flat red gasket was not creating any issues. There was no leak with the red gasket installed. The leak occurred after the lube was drained/replaced. The tech may not have replaced the old red gasket with a new one.

The red gasket was replaced with a flat black gasket then the "O" ring.

The boat won't go near the water until the leak is corrected.

The leak is definitely not at the vent plug but rather at the drain plug.
also not coming through the rear prop shaft seal.

The dealer has yet to articulate what the cause is - they're just changing
out gaskets. I do know they did not have a new drain plug in stock. They may have ordered one when they put in the "O" ring.

I hadn't considered that the tech may have tried to put the vent plug in the drain hole - its possible. Its also possible the tech cross threaded the threads. When I took it back the first time, a different tech did the replacement and when he hand threaded the drain plug in he said it stopped,
feeling like there was a burr or something in there but eventually he was able to screw it down to the seat against the gasket. That may have exacerbated
the problem.

If the threads are damaged, and if they tried "chasing" them before they
put in the "O" ring and it didn't stop the leak, perhaps it may require going to
a larger drain plug from a larger gear case (if they make larger plugs) and re-tap the hole for the larger plug If there is enough room up there to take a larger plug.

What a mess. All because I was too lazy to do it myself. Will know more
tomorrow when I inform the dealer he hasn't treated the cause of the leak yet.

I would insist, when they remove the drain bolt, to see the threads on the LU. The metal SS drain bolt would survive easily.

Sounds like the original tech, cross-threaded the screw, then installed an O-RING to "get by".

If the threads are messed up, your best off (either them or machine shop), installing a heli-coil or time sert.. It'd be the same size threads when done AND, you now have STAINLESS STEEL threads, much stronger than the aluminum.

Look at the parts fish for your engine:
2006 and Later F25LA Yamaha Outboard LOWER CASING DRIVE 1 Diagram and Parts

(deleted wrong information)...


*Just as a side note, I install heli-coils in carb float bowls in generators to make sure they can be FULLY drained. But, I use RED loctite, wipe out excess and let dry over night. Those threads are NOT going anywhere.(You can say overkill but I don't have and comebacks or"do overs" with my customers.).

The aluminum below is maybe 1/3 as thick as your LU (but now has plenty of threads):

[dray0151]

[QUOTE=TownsendsFJR1300;149363]I would insist, when they remove the drain bolt, to see the threads on the LU. T

Look at the parts fish for your engine:
2006 and Later F25LA Yamaha Outboard LOWER CASING DRIVE 1 Diagram and Parts TWO different part #'s for each sealing washer.. Odd, why improve/change one and not the other.. I don't believe the thread size is different, just the lower bolt is magnetic..
/QUOTE


Townsend I think the actual part number is the same just shown as 29 an 34 but has part # 90430-08020-00 unless I am seeing wrong?

[TownsendsFJR1300]

Townsend I think the actual part number is the same just shown as 29 an 34 but has part # 90430-08020-00 unless I am seeing wrong?

No, your correct. I don't know why they did it that way. Doesn't make sense but what's new..

The same anodes thru out (at least my engine), will show say part #29 on all of them...