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Old 18-07-2015, 21:04   #1
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Stripped thread in impeller housing. Now What ??!!

The impeller was getting old, so I replaced it. However, although I was being very careful not to use undue force, one of the holes in the impeller housing/dome got stripped as I was attaching the housing/dome back to the engine. The other two bolts are OK. Two solutions:

1) Get new housing/dome.

2) Drill larger hole in impeller housing/dome, tap it and insert larger diameter bolt. (Concerned about strength of hole once more metal is removed - not much to spare on the circumference of the housing/dome now).

Any other suggestions ?

It's a Sherwood G02 pump.
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Old 18-07-2015, 22:24   #2
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Re: Stripped thread in impeller housing. Now What ??!!

There are a number of products like helicoil, etc., that replace the bad threads with new ones the original size. They come in kits that include a drill bit, tap and new threads. The advantage is the hole is only opened enough to install the new threads. The insert is like a bushing threaded on the inside and outside. The insert is usually stainless. If put in with locktite, they become permanent.
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Old 18-07-2015, 22:30   #3
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Re: Stripped thread in impeller housing. Now What ??!!

Quote:
Originally Posted by macbeth View Post
The impeller was getting old, so I replaced it. However, although I was being very careful not to use undue force, one of the holes in the impeller housing/dome got stripped as I was attaching the housing/dome back to the engine. The other two bolts are OK. Two solutions:

1) Get new housing/dome.

2) Drill larger hole in impeller housing/dome, tap it and insert larger diameter bolt. (Concerned about strength of hole once more metal is removed - not much to spare on the circumference of the housing/dome now).

Any other suggestions ?

It's a Sherwood G02 pump.
I'm not familiar with this pump but...
Can you drill two smaller holes either side of the stripped one
or
Can you drill right though and use a longer bolt and loose nut.
or
Can you use metal set in the stripped hole and loosely fit bolt coated in silicone grease. Tighten after metal set has gone off.
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Old 18-07-2015, 22:40   #4
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Re: Stripped thread in impeller housing. Now What ??!!

Do it right, use a Heli-coil. Easy peasy.
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Old 19-07-2015, 06:09   #5
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Re: Stripped thread in impeller housing. Now What ??!!

I like wotname's suggestions. However what is "metal set" ? If this does not work I"drill right through. Thanks


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Old 19-07-2015, 10:42   #6
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Re: Stripped thread in impeller housing. Now What ??!!

I'd try some thread sealer like Loctite first. Obviously it wont help if there's no thread at all, but if there's a little then might be worth a try. Also use a new bolt, as typically the bolt will have lost some thread too.
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Old 19-07-2015, 11:28   #7
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Re: Stripped thread in impeller housing. Now What ??!!

Drill and tap a new thread for all of them, and if the next size up imperial thread is too big a jump, try a metric size, there might be one in-between.
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Old 19-07-2015, 11:34   #8
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Re: Stripped thread in impeller housing. Now What ??!!

If there is enough room, the best fix would be a stud with a nut and washer to hold on the cover.
With a stud it could be as simple as drilling and tapping just a few threads deeper and using devcon 200 or some other metal filled glue to fill around the stud in the old stripped hole.
The beauty of the stud is it does not ever have to be removed from the pump for service.
Take any machining to a machine shop where there are enough tools and knowledge to get a worth-while repair accomplished. Never attempt to drill and tap using a portable drill unless it is an emergency.
By the the way a heli-coil requires a much larger hole than the bolt being replaced. Heli-coils are mostly used to install stronger threads in low strength metals.
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Old 19-07-2015, 12:15   #9
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Re: Stripped thread in impeller housing. Now What ??!!

Macbeth

I agree with Oleman devcon (or similar ) and a stud have done it on my old yacht . Maybe just a longer stud will screw deeper into the thread .
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Old 19-07-2015, 14:05   #10
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Re: Stripped thread in impeller housing. Now What ??!!

If there is room a helicoil will restore the original thread if space is available. If not, just try and use the tap for the original size thread to clean out the impeller side and then the die to clean up the screw that goes in, or replace the screw with a new one. Once you do that you may not need to use the helicoil. Next best bet is helicoil. I'd stay away from the loctite idea unless it is an emergency and you need to get underway NOW.

Reference: 10 years navy experience working with electromechanical weapon systems repairs. 5 years working on my own boat and cruising Mexico.
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Old 19-07-2015, 14:10   #11
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Re: Stripped thread in impeller housing. Now What ??!!

Quote:
Originally Posted by macbeth View Post
The impeller was getting old, so I replaced it. However, although I was being very careful not to use undue force, one of the holes in the impeller housing/dome got stripped as I was attaching the housing/dome back to the engine. The other two bolts are OK. Two solutions:

1) Get new housing/dome.

2) Drill larger hole in impeller housing/dome, tap it and insert larger diameter bolt. (Concerned about strength of hole once more metal is removed - not much to spare on the circumference of the housing/dome now).

Any other suggestions ?

It's a Sherwood G02 pump.
A Helicoil should fix your thread fine. I'm not sure what size you are talking or whether it's a blind hole. A Helicoil does not enlarge the hole very much at all. Only by the depth of a thread. You can do it easily yourself but use a drill press to keep the pilot hole square. Any engineering workshop will do it for not very much as it would only take me 30 minutes to do. Google Helicoil for more info.
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Old 19-07-2015, 16:28   #12
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Re: Stripped thread in impeller housing. Now What ??!!

Hi

are you talking about the cover? when you say domes? if so there is not much stress on it. but drilling it out could make the hole too big even for a helicoil and drilling through wouldn't be good. But you can as suggested above, get some epoxy paste, such as steel putty, any auto parts will have it, clean the hole, leaving what threads there are and insert a small rod made from the epoxy and coat a new screw the same size and thread into the hole, with out the pate. when the epoxy is set, about an hour, back the screw out and install the cover.
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Old 19-07-2015, 16:31   #13
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Re: Stripped thread in impeller housing. Now What ??!!

I did the same on my johnson pump housing which had six screws so I moved to a speed seal cover - something I had planned to do but hadn't gotten around to - which works on four, works out fine!

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Old 19-07-2015, 16:56   #14
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Re: Stripped thread in impeller housing. Now What ??!!

Pretty much all of the solutions suggested so far will work.

I looked up a Sherwood "G02" and could only find a G2, does your pump look like this:



If so, I'd be tempted to replace the bolts with studs. The reason being that the housing is easier to install on to 3 studs than it is to hold in place with one hand and then run the bolts in with the other hand, much easier to put the housing on and then it stays there while you can start the nuts, and it is pretty much reversible if you ever change your mind. Use epoxy or locktite, and on the one that is now stripped see if you can either feed a bolt in from the back or epoxy a nut or two onto the back side.

Lastly, the simplest option is if you have this pump pictured is to install the 2 non-stripped bolts and then use another bolt the same diameter but longer and simply back it up with a nut as it looks like you have the clearance in the back.
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Old 19-07-2015, 17:13   #15
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Re: Stripped thread in impeller housing. Now What ??!!

Quote:
Originally Posted by macbeth View Post
I like wotname's suggestions. However what is "metal set" ? If this does not work I"drill right through. Thanks


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Metal set = devcon, steel putty, etc.

Helicoils are the proper fix but the others will get you going if you haven't acess to best practice!
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