Thread Repair - Helicoil, Keysert, or oversize hole?

[Tinkerer]

A couple of 5/16 UNC threads have stripped in the leg where the bolts go that hold the gearcase on my '67 Evinrude V4 60HP. It's exclusively a salt water motor.<br /><br />I don't know enough about metals and corrosion to know which is the best way to go.<br /><br />I have Keyserts but they're carbon steel and I assume they'll rust out in about 5 minutes and damage the alloy on the leg as well. I like Keyserts because they can be fitted with ordinary tools, but the hole has to be oversized to 3/8 to tap for the Keysert. There's enough meat to do it. I can get stainless steel Keyserts.<br /><br />You wouldn't believe how hard it is to find a 5/16" UNC Helicoil repair kit here, nor the price (about AU$60 versus about half that on eBay shipped from the US with postage included). But they're stainless steel (but maybe not marine grade) so I expect they're better than carbon steel. I'd rather not use them because of the cost and the fact I end up with a very expensive tap I'll probably never use again.<br /><br />The other possibility is to drill and tap the holes to take 3/8" bolts, which is the same size as the Keyserts. The bolt heads are on the underside so the difference in size won't be noticed. The issue then is what grade of 3/8" bolt I need and whether I can get it.<br /><br />Epoxy thread repairs won't work as they can't take the torque. <br /><br />I could use Loctite thread sealer on the carbon steel Keysert when I insert it and on the bolt when it goes in, but it's almost a certainty that some part is missed and corrosion will start.<br /><br />What's the best way to go?

 

[ob]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Since you got the room to oversize to 3/8" and the drill size to tap would be slightly less than 3/8" ,it's a no brainer.Just oversize up to 3/8" and you'll be set.I recommend 316 stainless if you can get it for the replacement bolt.Otherwise 302 or 304 will suffice.<br /><br />I use either no/oxide grease(sparingly) on the threads or any marine grade grease on assembly.

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

ob<br /><br />You're a champion, mate! That's the way I wanted to go, 'cos it's so easy.

 

[DHPMARINE]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Tinkerer, If helicoil is not an option go for the keysert stainless idea.If you oversize the bolt think about the wrench size.Can you get into there and tighten it up?And loosen up later to pull the lower unit?<br /><br />Actually,you say you have stripped 2,so buy the helicoil set,because more will let go and you'll be ready.<br /><br />DHP

 

[JB]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Both ob and DHP make sound arguments for their recommendations.<br /><br />I lean toward ob's suggestion because it is simpler and leaves only one interface of dissimilar metals.<br /><br />I haven't dealt with your exact problem, but I have solved many a similar problem by going a size larger and using the right bolt.<br /><br />Good luck.

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Thanks all. They're all good points.<br /><br />Although they sit in a recess the head on the oversize bolt is the same size as the originals, so access won't be a problem.<br /><br />The threads were stripped when I got the motor. I don't plan on stripping any more. Unlike the previous owner, I use a torque wrench and stick to the manufacturer's torques. <br /><br />I'll stick with the oversize hole because I end up with the same size hole as a Keysert but only two metals instead of three. Also, I can't find a helicoil in the right size (would you believe none of the major auto trade suppliers in a city of +3million people carry more than a few, all in the wrong size).<br /><br />Now for the laugh bit. I went to an auto supplier that is open on New Year's Day. The only SS bolts they had are metric. I couldn't remember the conversion but worked out that 3/8" is 10mm, by comparing drill bit sizes etc in the store as I couldn't find a vernier. So I bought the 10mm SS bolts which I discovered when I opened them looked a lot like 5/16", which they were because after all my careful checking of sizes I'd picked up 8mm instead of 10mm. Needless to say I worked this out about half an hour after all the stores had shut. Some things don't change.

 

[OBJ]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Just an added note here Tinkerer.....before you assemble the lower unit back to the midsection, coat all the bolts real good with a gasket sealing compound. This will help keep the corrosion down and the bolts from seizing.

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

OBJ<br /><br />This raises a point I've pondered at times (I do a lot of pondering standing in my workshop with a beer in my hand. In fact, I've been doing quite a bit of pondering over the Xmas break, as is attested by the small mountain of beer cans I'm cunningly secreting from my wife, by putting her empty champers bottles on top of my beer cans in the garbage bags so that she thinks she drinks way more than she does and won't comment on my drinking.).<br /><br />Are we better off using sealing compounds like the various Loctite products that generally harden to keep water and corrosion out or greases that probably wash out? I'm fond of Copper-Eze (a copper based grease) in auto applications but in marine / alloy ones I'm not sure it won't start up bad corrosion.

 

[OBJ]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

I use a regular gasket sealing compound that can be purchased at any auto store. It's fairly common and comes with a brush applicator. It's a brownish in color. Has very good adhesive qualities and works very well. I think I would stay away from locktite on the fasteners. Might make it harder to get them lose after a while. I coat the whole fastener when I'm using the compound. I've had real good results using the stuff.<br /><br />The other problem...(cans)...well.....hide them best ya' can....cans are easier to conceal than Bud Longneck Bottles.... ....why is it that pondering is easier with beer??????

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Originally posted by DHPMARINE:<br /> Actually,you say you have stripped 2,so buy the helicoil set,because more will let go and you'll be ready.<br /><br />DHP

You're right. The others aren't too flash either. I'll do the lot now. It will also avoid crossed threads in future when somebody (likely me) doesn't remember or realise that there are mixed sizes on the same fitting and forces a bolt into the wrong thread.

 

[lark2004]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

with the Gasket sealer, Permatex aviation gasket sealer (non-hardening) is what you want. You can get it from Repco(expensive), Autobarn(great if you want a radio!), or Supercheap(don't ask for help, the 15y/o kid behind the counter won't know, but the price is cheap). You probably already have some lying a bench somewear if you're like me and tinker on all sorts of engines.... (stainless helicoils are ok to use, since you are putting stainless bolts in the corrosion isn't any worse than before, but do not assemble dry, as stainless on stainless can bind(also called galling) very easily)<br />Good luck with it mate.

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Originally posted by DHPMARINE:<br /> Tinkerer, If you oversize the bolt think about the wrench size.Can you get into there and tighten it up?And loosen up later to pull the lower unit?<br />DHP

This is embarassing, but I'm used to it as I'm an idiot.<br /><br />DHP was right, so I should set the record straight.<br /><br />The same size bolt heads that I said were on the 3/8 were in fact on the 8mm 5/16 equivalent I'd picked up by mistake, not the 10mm 3/8 equivalent I meant to pick up. I attribute this clumsy oversight to my natural stupididy (how else could I pick up an 8mm bolt pack for a 10mm when I was wearing my glasses) compounded by excessive tiredness caused by prodigious consumption of beer over Xmas (if I'd slept normal hours I couldn't have drunk half as much).<br /><br />The heads on the only 10mm SS bolts I can find, there being no 3/8 SS I can find, won't allow a socket or spanner in the recesses.<br /><br />I am now the proud owner of a 5/16 Helicoil kit.<br /><br />I wonder what damage I'm going to do with that?<br /><br />Kids, don't try this at home!

 

[OBJ]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Tinkerer....the new issue of Trailer Boats magazine has a real good article on the use of Helix Coils. Don't know if that mag is in your part of the world or not, but if it is, it's worth the read.<br /><br />EDIT: Here's the link to their site.<br /><br /> http://www.trailerboats.com/

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

OBJ<br /><br />Thanks. I doubt we get it although there's a local mag with a similar title, but I'll keep my eye out for it.

 

[DHPMARINE]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Tinkerer,<br /> <br />Thanks,I was just trying to point you in the right direction.<br /><br />OBJ<br /><br />That article should be mandatory reading.I see more and more good things in Trailer Boats Magazine.<br /><br />DHP

 

[OBJ]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Indeed so DHP.....they got a good crew workin' for them.

 

[lark2004]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

obviously better than it's australian namesake, Their articals rarely look at maintenance or anything that the owner can tackle themselves. It mainly looks at all the new rigs and engines that we can only dream of ever owning.

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

Originally posted by lark2004:<br /> You can get it from Repco(expensive), Autobarn(great if you want a radio!), or Supercheap(don't ask for help, the 15y/o kid behind the counter won't know, but the price is cheap).

Mate, sorry I didn't respond on this one. Your last post jogged my memory.<br /><br />Indeed I do have some No. 3 aviation gasket on a shelf. <br /><br />Would you believe Repco down here carries hardly any helicoils, and the first Repco store I rang didn't know what they were. The next one checked the computer for all stores stock and there wasn't much there or in the warehouse.<br /><br />I'll stick with the engineering suppliers I usually go to but they weren't open over the Xmas-New Year break, which is the only reason I rang Repco.<br /><br />Autobarn is definitely the place to shop for overpriced steering wheel covers, fancy gearstick knobs, fluffy dice, and tools you can get at SuperCheap for half the price. <br /><br />SuperCheap is near and dear to my heart. Apart from the great prices on some stuff, as long as you can separate the rubbish from the useable, it's the only place where they pay me to shop.<br /><br />SuperCheap took over another auto parts place near me a couple of years ago and marked the acquired stock down, probably because it was too hard or costly to put it on their computer inventory for just one store. <br /><br />Over a few weeks, as they put it on the shelves, I bought a swag of stuff at about a third to half of normal retail that I couldn't have justified at full retail, like mechanic's stethescopes and stud removers and various engine rebuilding tools. Generally the sort of stuff you'll only use a few times but very handy when you need it.<br /><br />I have to confess that I dithered over picking up an assortment of helicoil kits at about $6 each (retail $45 upwards) but decided it would be dead money in the long term as I might never use them. Yesterday I paid $45 for one kit that would have covered about 7 or 8 kits at SuperCheap if I'd gone with my instinct instead of my head.<br /><br />But the SuperCheap jackpot was the digital verniers. I was looking in a locked cabinet for something else and saw some good quality steel analog verniers for $10 that were a good deal as they were usually about $50 to $60 retail anywhere else. Then I saw a digital one with no price. Got the 15 year old kid with the key to unlock the cabinet so I could check them out and they seemed pretty OK. <br /><br />I need a magnifying glass to read analog vernier scales. I've lusted after digital for ages but don't use verniers as true measuring devices often enough to justify the cost. <br /><br />I figured I might get lucky and pick up a digital vernier worth $120 upwards for maybe $40 to $50, given the way they were pricing their other stuff, although I couldn't see them cutting prices on higher priced tools like this. I'd buy one at $50 for sure.<br /><br />"How much are the digital verniers?"<br /><br />Kid ferrets around in the cabinet for a price. Can't find one. After a while he decides that the $10 price applies to the digitals as well. <br /><br />Bingo!<br /><br />I grab it.<br /><br />We go to the checkout and I'm convinced it's going to come up on the computer at a higher price. The kid looks at me and says: "These are a good price. They're worth more than $10.". Yeah, I think, at least $110 more. The kid is onto me. I'm waiting for the bad news. It's too good to be true. Then he keys it in as unlisted stock at $10. You little beauty! I am a winner!<br /><br />As I wander out to my car I'm thinking it's a pity to leave the other 6 digital verniers there 'cos they're such huge bargains. <br /><br />What am I going to do with 6 verniers?<br /><br />I decide I'll big note myself by giving them to mates. Then I realise that only one of my mates could have any use for a digital vernier.<br /><br />But I've just discovered eBay.<br /><br />So I figure this is a cheap way to try out selling on eBay.<br /><br />I go back and buy the lot.<br /><br />Put them all on eBay in the next few weeks and sold them between $70 and $110 each. Made around $500 profit for a few hours work. <br /><br />That started my eBay career and it's been producing an average of a couple of hundred bucks profit a week for the past 18 months. <br /><br />I owe all this to SuperCheap!

 

[lark2004]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

lol,<br /><br />I would normally just go to a bearing/nut and bolt shop for a helicoil set, CBC are OK, but expensive. I am lucky to have a good shop near me called Pine Rivers Bearings Nuts and Bolts, they have everything I need, and reasonably priced. The auto shops are next to useless for thread repair.

 

[Tinkerer]

Re: Thread Repair - Helicoil, Keysert, or oversize hole?

lark<br /><br />I actually got my helicoils from CBC 'cos they're close to work, but their prices were in about the same range as the other couple of places I go to. <br /><br />The large auto chains here are becoming more useless for anything that's not mainstream and high volume. The Repco stores near me have a much smaller range of tools than they did even 12 months ago and they're getting more like AutoBarn but still with a much, much better spares section.<br /><br />Another reason I like SuperCheap is that they have a decent trailer section in some stores which can also carry odd bits of marine stuff. Also much better paint and body repair stock.<br /><br />And what the %$^& is a Cheesy Poof? Do you put your poofs in cheese up north or what?