gearcase drain plug leak

[fairdeal]

You don't want a machined larger screw as now you won't have an adapter to re-fill the lower unit that fits...

Actually, a not-uncommon approach for a stripped Yamaha M8 plug is to drill and tap to 3/8-16

then stop by the Mercury dealer for a plug.

The plastic lube pump will now connect directly, no adapter needed.

[TownsendsFJR1300]

Thanks Tony,

Sorry to hear it but that's what I thought/posted earlier.

It sucks they screwed it up to start with, but to NOT tell you, and get it out the door sucks even worse.

Pretty sad a tech can't install a simple drain plug...

As their leery on doing a heli-coil, I would check local machine shops and have them do it. Let the dealer pay for it, perhaps pull the LU if the machine shop prefers it off.

As noted earlier, It can be heli-coiled W/O issue and you'll have steel threads being much stronger than stock aluminum threads. RB posted how many threads to remove from the coil.

You don't want a machined larger screw as now you won't have an adapter to re-fill the lower unit that fits...

Per another recent post, your correct with the thread size.

I'd find another dealer if possible for future repairs or DIY, you'll know it's done right...

Plz update once your up and running..



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[Tony Sopranzi]

leaky drain plug

Scott,
Took the boat back to the dealer yesterday. Over the weekend I bought
a new Yamaha plug and new Yamaha gaskets. When I removed the original plug they had installed with the "O" ring I knew by how tight it was screwing out that it was cross threaded. the "O" ring and plug head had what appeared to be failed sealer of some sort. For the record I tried the new plug and new gasket. Screwing in the plug was just as tight going in - definitely crosse threaded. I had to try it myself. So tight you cant feel the gasket seat in the hole. With one gasket it leaked. We tried a double gasket and over a period of about 2 -3 hours the plug was collecting oil in the screwdriver slot and forming a droplet. Also measured the plug and thread pitch which worked out to be 8mm w/a 1.25 pitch. I found a 8/1.25 nut at Ace Hardware and it threaded on the original plug nicely. It also threaded nicely on a 8/1.25 tap. Yesterday morning I took the boat down and presented my findings to the service dept. I told them Yamaha wouldn't be very happy seeing a "O" ring and sealant on one of their drain plugs, demonstrated how the plug should feel going into the hole with the nut on the plug and told them they needed a "tapered" tap so it would line up with the hole and keep the tap straight. Also mentioned they should turn the tap
a couple of turns then back it out a half turn repeatedly as they tapped out the threads. They either get a successful tap, if not re-tap for a larger plug,
or heliicoil (which they don't wish to do) or replace the gear case casting. Ball is in their court. will let you know how it turns out. They'll probably keep it a few days.

[TownsendsFJR1300]

Update?

Any updates Tony???



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[Tony Sopranzi]

leaky drain plug

Thanks all for the nice comments on the boat. It was built (not by me) off of
Nexus Marine (Seattle Wash) plans here in Florida. All I did was clean it up,
put new trim tab cylinders on it and a few other things, sand the brightwork and give it a refresher coat on all the varnished surfaces. Nexus Marine calls it a "San Juan Dory" after the San Juan Islands up there on the Northwest coast.

[TownsendsFJR1300]

Definitely a very neat boat!!

[panasonic]

what a nice boat! Who ever built that is certainly a craftsman. My father, grandfather, great grandfather all built wooden boats..from punts to small schooners.My cousin has built 17 boats so far.. I love the feel of a wood boat in rough weather...a lot more solid under your feet. Not many building wood boats anymore.

[dray0151]

Oh my gosh!!!! I'd be afraid to move that out of the garage!!!!

[DennisG01]

That's a pretty Dory. My mother, now 70, tells me stories of being a kid and using a Dory to get from one place to another up on the coast of Maine (her, her 4 brothers and parents). I've seen old pictures of their Dory... it never looked like that! It got them where they needed to go, though!

[boscoe99]

That garage looks better than my living room.

[boscoe99]

I would think the cases would be drilled in a jig so that the screw plug would be centered in the hole. If thats the case, this plug is apparently fitted in there at an angle. Will confer with the dealer tomorrow. I'm not fond of
helicoils, but I'm afraid thats where he'll want to go rather than eat a new gear case.

Why not? Some Yams come with them already installed. Many engine makers use them in production, particularly when soft materials such as aluminium are being used.

[Tony Sopranzi]

Boat leaky gear case is on

16' Dory - enjoy the photos.

[rl=https://postimg.org/image/d6nbc991r/][/url]

[TownsendsFJR1300]

Simple, pull the plug, inspect threads, surfaces, plug...

If they buggered up the threads, you can always yank the LU and bring it to a machine shop. I don't think I would trust them for this repair IF the tech cross threaded a simple drain screw.

I wouldn't hesitate using a heli-coil BUT getting the angle correct (perpendicular) is super important..

*I would think, in the machining process at the factory, that hole and threads
are all cut/machined at the same time.

[Tony Sopranzi]

leaky drain plug

I know - its so funny - 5 pages now. Must be a record lol. Lots of very good
analysis though. I too thought perhaps it was wicking from the raised end of
the screwdriver slot and collecting at the hole. Good possibility. Soooo,
under very close scrutiny (laying on my back armed with a halogen flashlight, Q-Tip, paper towel and a very small thin bladed slot driver, I was able to determine that there is no oil in the upper end of the slot. There is some oil residue on the lower end of the slot. There is no relief hole through
the top of the screw head down into the magnet cavity. The screw head is
not centered in the hole - its offset high and to the upper right of the hole looking at it head on (laying on my back). There is oil between the screw head and case on the upper right and its flowing down to the bottom of the case hole. There is no longer a droplet on the screw head. moving around clockwise there is more space at the bottom and lower left between the screw head and case hole then the gap tapers off as it nears the top of the case hole I didn't see an oil concentration on the upper left of the screw head. Looks like most if not all of it is on the upper right draining down the case hole to the bottom and out. The sage who suggested the oil may be migrating up the screw driver slot and draining from the center hole is closest to the truth. I think as the oil accumulated on the right side it found
a path in the screw driver slot and the pressure from the leaking oil just pushed it up the slot to the hole and out.
I would think the cases would be drilled in a jig so that the screw plug would be centered in the hole. If thats the case, this plug is apparently fitted in there at an angle. Will confer with the dealer tomorrow. I'm not fond of
helicoils, but I'm afraid thats where he'll want to go rather than eat a new gear case.

[DennisG01]

Regarding the idea that the hole goes all the way through the plug. Thoughts... All manufacturers use a magnet in the drain plug and nearly all of those plugs do not have a hole - meaning, I don't think the hole is there for "venting" during the installation of the magnet. Secondly, from one of the earlier pictures that were posted, it appears the depth of the hole is very shallow - it even looks like you can see bottom of the hole as it looks like you can see where the drill stopped drilling. You know how when you stop drilling, the bottom of the hole is "angled" to match the drill bit?

Have you tried putting a screwdriver on it yet and "feeling" how secure it feels?

Because of the angle that the plug is at under the gearcase, it is quite possible for oil to leak out from around the plug head, start to collect at the bottom of the plug head, but also wick it's way slightly uphill as the oil collects, before eventually dripping off.

Clean the area VERY well and then closely observe it. It shouldn't be hard to figure out where the leak is coming from.

I mean this in a fun way so please don't take offense... Holy crap, we have nearly 70 posts about an easy to identify leak source!