Stripped Inside Lower Unit Threads and repair solutions

[Bergertime]

Dropped by the storage yard yesterday to bring back some ropes and stuff and I noticed that one of the lower unit mounting bolts was missing.  My motor,  98 Johnson has 4 of these that bolt up under the cavitation plate.  Went to Home Depot and found a replacement but when I was putting it back in I found that the inside threads are now stripped.  I was a little surprised by this since I had the lower unit off a month or so ago for an impeller replacement and this was not noticed.  

Anyway, looking for suggestion on how to remedy this..  In doing some research I have found there are a couple suggestions out there and I am wondering what would be the correct way to fix.  Is there a short term fix I can put into place so I can use the boat until work can be scheduled.

Option 1: Drill and/or thread the hole to the next larger size

Option 2: Use one of the thread insert products on the market which involve drilling a larger hole and inserting a new thread insert

Option 3: All ears?

Once again.. Hoping for a mechanically inclined suggestion :)


Bruce

[seabob4]

I'd go with a Heli-coil.  Ask Marc, Aerospace uses millions of them.  Determine the thread size of the current bolt (most likely 3/8-?), then buy the kit that restores the hole to that thread size...

That's what I would do...

[John Jones]

Yep, helicoil.

When I bought my 60 Yamaha used I was going to replace the water pump and such before I put it in the water.  One of the lower unit bolts brought the threads out with the bolt.  Just carefully drill the hole with the proper size bit and screw in the helicoil you are done.  It has held up for six years with at least 3 water pump changes with no issues.

Figure out the bolt size and thread pitch and you can buy a kit with the proper tap, and insertion tool as well as a few coils.  The package will tell you the proper drill bit size.

http://www.amazon.com/Helicoil-5546-9-M ... s=helicoil

[Bergertime]

Thanks all for the suggestion.

[wingtime]

Yup Heli coil.  should be able to find a kit.  You drill and tap it and then thread in the helicoil.  The Helicoi is stainless so you will have stainless threads so it will be stronger than new.

[GoneFission]

Make sure you use a stainless model if you do the heli-coil thing.  Another option is Durafix (a low temp aluminum filler) - clean and fill the hole, then drill and tap with the correct bit and tap.  Durafix info is at:  http://durafix.com

[fishnutz]

After 30 yrs in the auto service biz, have not used any Heli-Coils in over 15 yrs.....much stronger and permanent repair using Time Sert repair kits, easily found on the internet   www.timesert.com


Rob

[RickK]

Maybe this is an opportunity to capture this info in the Resources forum for these thread repair options.  I'll move the topic.