Frozen Dain Plug

[xenus7850]

OK, this has really been a project and need some expert advice. I have a frozen drain plug on my lower unit (merc. 2004 5.0). I haved used a large screwdriver, heat, impact screwdriver, punch, etc. Finally I tried to easy out it, but still no go. I have now taken the lower unit off and have managed to free it, but now have a new problem. When trying to easy out it, I drilled though the threads on the lower unit, particularly where the o-ring seats. I cannot get the drain plug out now as it stops when it gets to that section. I am sure that I will have to have it drilled out. What can I do though to get a new pug in there to seal? Do they have over sized drain plugs to accommodate? Anyone now if there is still a drain plug behind the prop on a 2004 merc B3? I have not looked yet. Thought of it after the damage was done. I don't know if by chance there is a drain on the bottom and behind the prop. Would I be able to take it to a machine shop and have them drill the old one out, re-drill a bit of a larger hole and have them make me a new drain plug to fit? I am looking for options here. If it turn out that there is an extra drain plug behind the prop, what about welding the one at the bottom in the lower unit closed and then just using the one behind the prop going forward. Please help with any options that you think would be of help.

 

[northernmerc]

Re: Frozen Dain Plug

You certainly have a problem there! As you mention, the first thing to check is if you have that second drain hole behind the prop. If so, get the old plug out and plug the damaged hole. Some JB Weld on a new drain plug should seal that permanently; likely no need for a welder. (However, pity the poor next owner who tries to get that loose.)

If you don't have a second drain hole, then take it to a good machinist and have them drill an oversize hole at the present drain location and tap it to an oversize. There may not be much extra metal to work with around that hole, so you might want to pay to have this done right - unless you are confident in your own skills.

 

[mla2ofus]

Re: Frozen Dain Plug

If you don't have the second drain plug, and if the hole is approx. 5/16", tap it w/ 1/8" pipe thread and find a brass 1/8" plug w/ allen head. If you can't find a brass one, use steel w/ lots of antiseize on the threads. The reason I suggest allen head is so it will be flush or close to it.
Mike

 

[xenus7850]

Re: Frozen Dain Plug

Ok, I called a dealer and a marine shop, the are both telling me to buy a new lower unit housing for my B3, which is about $800-$1000. I can't believe that I cannot fix this problem besides replacing the LU. Here is what I am looking to do, please let me know if this will work.

I plan on having a machine shop machine the LU drain hole out to 3/8 inch NPT, then I plan on putting a recessed (allen fitted) 3/8" NPT stainless steel plug in there. I would assume that I would need to use some plumbers tape just to make sure it is water tight.

My question is, should this work? Will it be water tight? I leave my boat in the water for about 6 months at a time, any concerns about water seeping in? Any issues that I have not thought of, or a better way to do this?

 

[ifixf18s]

Re: Frozen Dain Plug

Interesting problem you have there. I had a simular problem on my engine but it was for the thermostate housing, The bolts broke the easyout broke I had a mess. This is what i did to fix it, I got a dremil tool with a bit about 1/8 Dia. I was able to start in the hole i drilled in the center of the bolt, then i slowly worked my way outboard, using plenty of lubricant, i used PB Blaster found at the auto parts store. Need to be careful and have a firm hand, and have plenty of light so you can see well (through safety glasses). Go a little at a time around whats left of the plug, when you start to see the Threads showing stop and use a tap to clean out the rest of the threads. Thats what i did for the thermostate housing bolts. It took a lot of patientce. Here is a little advice on easy outs. Its very important as you probably know to be in the center of the bolt, ect. sounds like you was off the center quite a bit, trying to steady the drill bit with the slot in the plug. Next time try using a ball file with the dremil and file down the slot making a concave shape in the center then use the drill bit,should keep you in the center. If this works for you i would think that you might want to flush the lower unit the best you can since there will be metal contaminates in it. Good luck

 

[northernmerc]

Re: Frozen Dain Plug

Ok, I called a dealer and a marine shop, the are both telling me to buy a new lower unit housing for my B3, which is about $800-$1000. I can't believe that I cannot fix this problem besides replacing the LU. Here is what I am looking to do, please let me know if this will work.

I plan on having a machine shop machine the LU drain hole out to 3/8 inch NPT, then I plan on putting a recessed (allen fitted) 3/8" NPT stainless steel plug in there. I would assume that I would need to use some plumbers tape just to make sure it is water tight.

My question is, should this work? Will it be water tight? I leave my boat in the water for about 6 months at a time, any concerns about water seeping in? Any issues that I have not thought of, or a better way to do this?

If the machine shop does this properly, it should work. The machine shop should be able to tell you if it will work when they see it. Teflon tape on the threads may help keep water out and oil in, although it would be better if you can use another seal, much like the original plugs have, as well.

I would recommend disassembling the lower unit before having the work done. You don't want filings in there with the gears.

 

[xenus7850]

Re: Frozen Dain Plug

OK, good news first, it appears that drilling and retapping to 3/8 NPT has done the job. I flushed the LU out using diesel fuel (4 Gallons) and made sure that I could get every shaving out of there after it was drilled and retapped to 3/8 NPT. Then a let it set and made sure that all the diesel fuel was out, then filled the LU up with 10w 40 to make sure all was out and then drained that out real good. When I had 10w 40 in there though, it leaked a tiny bit from the new drain plug, but I had yet to really tighten it down. I applied some liquid plumber paste and tightened it down good and it appears to be holding.

The bad news (maybe), I have reattached the LU 3 times now, however the seams to be a VERY VERY SLIGHT gap in the very front by where the shaft goes into the upper housing, actually even in front of that by where the water drain hole is. It is in the very very front of the lower unit by the back of the transom. I would say it is about 1/50 of an inch, like I said, VERY VERY small and the length is only about 2 inches.

Can this be normal? If not, what should I do? I don't know if it was always like this as the LU and UU have had bottom paint on them, so that small cracked would not have been noticeable then.

 

[northernmerc]

Re: Frozen Dain Plug

I can't say for sure since I don't have the same model of motor to look at. But as long as everything seated well and tighened up good, you should be OK. It might be cast that way. If this is in the spot that I think it is, you have no gasket there and aren't trying to keep water out of that area anyway. Please correct me if I'm missing something.

 

[chuckb]

Re: Frozen Dain Plug

Hi,

I discovered a great way to losen frozen drain plugs or any other aluminum or heat sensitive parts. Buy yourself one of those portable steam cleaners such as sold by Shark, Monster, or any other you may see on those obnoxious late night infomercials. A few minutes of hot concentrated steam at the stuck part will losed it up. The steam is only a few degrees below boiling (100C/212F) and will not damage your lower unit. In fact, I've found that the steam also seems to break-up the oxidation that usually causes stuck aluminum parts.