Lower Unit Plug Repair--STEP 1 - Striper Talk Striped Bass Fishing, Surfcasting, Boating

Van · 02-22-2007, 05:06 PM

Well that freakin' lower plug on my engiine finally stripped the threads on the gear case. I took the LU off and brought it to the dealer. They gave it a valiant try by drilling out the case, and installing a helicoil for the plug. But it would not hold during the pressure test.
The helicoil is not perfectly aligned to let the plastic washer make full contact.

We talked about a few fixes (such as just sealing right over the plug with marinetek or like) and forgetting about it. But I am way to picky to do that. Sooooo I took the LU home and talked to my machinist here at work. Heres step one of the plan. I will remove the helicoil and see what depth of metal remains. Seems there is plenty of material before I'm into the gearcase for some new threads. I removed the carrier to access the inside of the plug hole.

Van · 02-22-2007, 05:08 PM

Once carrier is out, can barely see back side of hole in pic (at about 3 o'clock)

More to come as I progress..

macojoe · 02-22-2007, 07:57 PM

I had to do this 20 years ago on a 74 Johnson,

After you get that shaft out you will need some long snap ring pliers to get the rest out.
I used needle nose vise grips and ground the tips small this way I could grab the split ring and then use the screw on the handle to closer up the ring so it comes out, same for going back in, put it in and unscrew to let the ring open back into place.

its easy when you get there, just drill and tap new hole, clean all meteal shavings out and reassemble.

Good Luck!

TheSpecialist · 02-22-2007, 08:13 PM

Won't that require a larger plug??

Van · 02-22-2007, 08:55 PM

MJ, I'm not going to remove the shaft. I can get to the back side of the hole and put a rag there or someting to catch the drillings. I heard putting heavy grease on the drill bit keeps more filings on the bit.
I might just clean out the case with brakecleen when I'm done to make sure all the pieces are out.

Spec, its not going to be a regular plug like we have now, the 1/4 npt is larger than the hole there now.
If not, I can go to 3/8" npt also, but I should be OK. As I progress we shall see.

I will post as I go.
I wnat to replace the shaft seal before I'm done too.

Raider Ronnie · 02-22-2007, 09:02 PM

How the heck did you strip the plug anyway???
Your motor isn't that old !!!

thefishingfreak · 02-22-2007, 09:59 PM

whats the problem? it leaks during pressure test? looks like a decent fix there. maybe you got the wrong washer in there.

take the helicoil out and put a bigger drain plug in there. your gunna need a bigger plug anyways if you start drilling.

thefishingfreak · 02-22-2007, 10:02 PM

the helicoil is crooked, i read too fast..

the case is soft enough a good tap should cut nicely without the drill.

Raider Ronnie · 02-22-2007, 10:09 PM

Looks like an excuse to get rid of that loud,gas guzzling, smoky 2 stroke and get an etec or a 4stroke if you ask me !!!

JohnR · 02-22-2007, 10:25 PM

How about replacing the nose cone with one of the freshwater tpyes - check out ScreamandFly.com and do a search there...

Van · 02-23-2007, 08:47 AM

Quote:

Originally Posted by thefishingfreak

whats the problem? it leaks during pressure test? looks like a decent fix there. maybe you got the wrong washer in there.

take the helicoil out and put a bigger drain plug in there. your gunna need a bigger plug anyways if you start drilling.

The shop that put the coil in said there are no plugs that are bigger, even from another manufacturer. The coil was so crooked I could see the impression in the plastic washer all on one side.

The problem is if I go to another bigger machine thread the head will be huge for that diameter and it will stick way out of the LU. So I think the good solution is the tapered pipe thread and a NPT plug. We use these things at work to hold thousnands of psi. It should hold fine for under 20. If all goes well it will be recessed just right and there will be very little flow disturbance in front of the prop.

Van · 02-23-2007, 08:50 AM

Quote:

Originally Posted by Raider Ronnie

Looks like an excuse to get rid of that loud,gas guzzling, smoky 2 stroke and get an etec or a 4stroke if you ask me !!!

4 STROKE NEVER !!!!
LOVE MY 2-STROKE !!!!
But an new 225 e-tec would be nice.

Van · 02-24-2007, 03:15 PM

packed the inside of the case with a rag to catch drillings, drilled out the old hold 7/16" then started to tap with the pipe tap.

I went a deep as the tap could go, but its a blind hole so it would not go as fara s I needed. by putting the plug it it sticks out too much.

So back to my shop and my I'll cut 1/4"-1/2" off the tap.
That should get the taper deep enough so the plug will be flush or just recessed.

Also picked up new seals for the prop shaft and drive shaft, a new o-ring and zinc for the carrier.

I'm getting there and it looks like it will work, the pressure test will tell.

Mr. Sandman · 02-24-2007, 03:41 PM

That looks like it should work. If not, I am sure you can find another lower unit pretty cheap from a blown or tired 'rude. What is that a 175? Zac's has one for a 150, I think that it is the same shell.

thefishingfreak · 02-24-2007, 03:45 PM

what about the little magnet in the drain plug?

Raider Ronnie · 02-24-2007, 03:55 PM

You using a tapering tap or a bottom one ?
You need to finish it off with a bottom tap.

Van · 02-25-2007, 01:39 PM

Sandman-The local shop said they can find a LU from a blown engine and swap out the guts. But the labor costs will be a killer, I don't think i would tackle that big a job. But if this fails, thats my only option.

Mike-I am moving the magnet to the top plug may not be the best but better than nothing. At the end of the season, I will run the LU in the driveway to get it all mixed up then dump it, it will come out pretty quick through that new hole.

Yea Ronnie its a tapered tap, I used 2,, the first was the slow taper type then I uses the one in the pic. It is almost bottoming, but I cant drive it in too far because of the shape of the case. Thats why I'll cut it and tap again, I'll cut it twice if I have to,. I'll finsh off with teflon tape and thread sealant. (not sure which kind yet).

I will post results, this may come in handy for others.

Van · 03-25-2007, 08:33 PM

Installed all new gaskets and seals--prop, main shaft, shift rod, carrier, and all the orings. Put on the new water pump, and pressure tested from the top oil overflow and the "all new" bottom plug. Held 14 psi in both directions !!!!

Filled her with oil and she is ready !!!

Just got to touch up the paint on the cone and install, bring on those basses !!!!!!

Van · 03-25-2007, 08:34 PM

Pressure tested and passed !!

Squid kids Dad · 03-25-2007, 08:41 PM

Good job Van

Mr. Sandman · 03-30-2007, 05:54 PM

Nice work. I am glad you got it repaired....its always something with boats eh?

Van · 03-31-2007, 09:07 AM

Quote:

Originally Posted by Mr. Sandman

Nice work. I am glad you got it repaired....its always something with boats eh?

Yea, I thought this would be the year I did not have to work on anything. NOT....

1) Lower Unit repair
2) New GPS install
3) New and improved floor drains and scuppers
4) Home made outriggers