# stripped threads



## bobberboy (Aug 25, 2010)

Can someone tell me what the implications of this ad are? This is the kind of motor I want for my current project.

https://minneapolis.craigslist.org/dak/boa/1918981501.html


The listing is long gone. It was for a '62 Johnson ss 40hp with stripped threads. The threads turned out to be the bottom cylinder spark plug hole.


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## Usmctanker (Aug 25, 2010)

A good machine shop can drill and tap the block. Shouldn't be a huge deal. I bet you could even call a shop and get a rough estimate.


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## hossthehermit (Aug 26, 2010)

Consider the possibility that this may be an excuse to make a compression check difficult. Just sayin'


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## bassboy1 (Aug 26, 2010)

What threads are stripped? From the sounds of it, there was a big problem anyway (seems to imply cyl. head or possibly crankcase, my bet is on the former), and when going in there to fix it, they really buggered something up.


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## Pappy (Aug 26, 2010)

I believe the reference is to the common 14MM spark plug threads - an easy, at home repair using an insert purchased at any Napa store. One head gasket and one insert and you are back in business. Heck of a price on that vintage engine as well! Those were excellent runners and you can't go wrong if that is the only issue minus the normal servicing of fuel and ignitions systems. If that were near me it would already be at my shop!


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## bobberboy (Sep 1, 2010)

Pappy said:


> I believe the reference is to the common 14MM spark plug threads - an easy, at home repair using an insert purchased at any Napa store. One head gasket and one insert and you are back in business. Heck of a price on that vintage engine as well! Those were excellent runners and you can't go wrong if that is the only issue minus the normal servicing of fuel and ignitions systems. If that were near me it would already be at my shop!



I finally got a response yesterday. Guy was out of town. It is the plug thread so I'm going to see it next week.


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## bobberboy (Sep 16, 2010)

I brought home the motor tonight for $25. The owner is retired but used to repair outboards. He has a shop connected to his garage just for his outboard work - pretty sweet. We had spoken on the phone and I told him about the 18hp Johnson I had from my runabout project - https://www.tinboats.net/forum/viewtopic.php?f=4&t=14785 - and he offered to trade me even up for the 40hp so I said yes. When I got there he looked at my motor and noticed the paint was discolored around the bottom cylinder head and told me that was from overheating and probably meant a scored cylinder. I assumed he knew what was what and it really wasn't good news for the 18hp. The starter was good and the lower unit too so he still offered me a trade of my motor + $25 for the 40hp and I took it. The 40 has electric start, fuel pump, automatic choke and the lower unit had been replaced at some point. The paint is pretty good too - it must have been stored indoors. My 18 was so sun-bleached you could hardly read the name anymore. I do have to deal with the bottom cylinder spark plug hole being stripped but compared to the 18 that seems pretty simple. I am glad to not have to do all the work to the 18 as motor mechanics isn't my strong suit. I also found a guy nearby in Wisconsin that said he'd take my '52 Johnson 5hp towards the labor to get the 40 running if I decide to have a pro do it instead of me. All-in-all I think I did ok on the trade - we'll see.


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## Hanr3 (Sep 16, 2010)

Helicoils.

Simple screw type insert to replace stripped threads. Used on engines and other parts allt he time.

https://www.helicoil.in/helicoil.htm


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## Ranchero50 (Sep 16, 2010)

Kind of an odd story. Does the 40 look like it was taken apart for inspection or anything? Seems odd he's trade you for a 18 that needs work without fixing up the 40 to make some decent money off of it. Just really odd.

For the stripped hole, I would first eBay a replacement head if possible, then it's only a gasket to make it 'right' if that's all that was wrong with it. Heck, I'd pull the head off just to check the bore condition and keep from contaminating the engine with metal while doing the thread repair. I wouldn't do the repair on the engine. The NAPA kits are great and can save a lot of grief on difficult engines.

Helicoils are frick'n junk, garbage, not intended for this application. Helicoils are for repairs that are not going to be taken back apart, ever. look up Key-sert, thet are a solid threaded insert that works very well. We use them often, either comercial ones or shop made for different applications.

Jamie


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## Quackrstackr (Sep 16, 2010)

Ranchero50 said:


> Kind of an odd story. Does the 40 look like it was taken apart for inspection or anything? Seems odd he's trade you for a 18 that needs work without fixing up the 40 to make some decent money off of it. Just really odd.



That's exactly what I'm thinking. The guy runs a repair shop and doesn't fix that himself?

I don't know what was wrong with your 18 but I hope he didn't see an easy mark coming...


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## perchin (Sep 16, 2010)

Quackrstackr said:


> Ranchero50 said:
> 
> 
> > Kind of an odd story. Does the 40 look like it was taken apart for inspection or anything? Seems odd he's trade you for a 18 that needs work without fixing up the 40 to make some decent money off of it. Just really odd.
> ...



I'm afraid I have to agree...... you see this kind of stuff on craigslist all the time...."just needs a little tlc....just needs carb cleaned, just needs a $15.00 part" .....well if its so easy, than why do these people not do it themselves and make a lot more money off a perfectly running machine???? probably because it really means there is more to the story.

I hope yours is not one of them cases.


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## Pappy (Sep 16, 2010)

It's an easy, do-it-yourself, repair. Best way is to remove the head as has been mentioned earlier. No need to look for a replacement head though unless the head is damaged beyond the plug threads. NAPA does have the correct "Non-Heli coil" type of insert that you drill and insert than tap to seat. They hold incredibly well and are extremaly easy to use. I use probably one per year on the engines I see. Have picked up a couple of very good engines in the last few years that have had this simple issue.


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## bobberboy (Sep 17, 2010)

I don't know ho to respond to any of the above questions. What I can tell you is he's retired and was clearing out his motor business as well. When I spoke to him on the phone he was immediately interested in my 18, and before he had seen it he offered an even-up trade (his 40hp was listed at $125 needing the head issue repaired). He had a few motors left in his shop including another 18 - he may have been intending to combine the two to make one good one. Maybe his 18 needed a lower end, I don't really know. Here's what I do know. I had an 18hp in pretty sorry condition. It was a long shaft and I couldn't use it. I could have sold it as a parts motor but I don't think for my purposes it was worth fixing. What I got was a 40 in return that is exactly what I was looking for. I don't know if I bought a pig-in-a-poke or not. You guys who fix motors maybe know what these would have been worth "as is". I didn't know how to evaluate that. I paid nothing for the 18 and so I paid $25 for the 40 horse. Whether I got screwed or not remains to be seen and I'll be sure to report, either way it goes. I appreciate all the comments and of course had wondered the same things myself. So, as somebody once said, "you pays your money and you takes your chances". Many years ago my brother bought a really sweet '58 Chevy that had sawdust in the rear end to keep the noise down. We'll see.

So what about the paint discoloration? When he pointed it out to me, the paint around the lower cylinder was definitely darker than the top one. That seems like a good indicator of overheating. The deal is done but I'm still curious. 

Now to the really important question. The helicoil or the new head? I want to do a good job of this because it's going on my current project boat.


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## Ranchero50 (Sep 17, 2010)

A helicoil is simply a peice of stainless wire that's coiled up inside and oversized threaded hole. The only think holding it there is the spring tension. They don't work very well in applications under vibrations or stress loads and are horrible on applications where you take the bolt in and out (like a spark plug). The usual senario is you'll be at the river/lake/ocean and foul a plug, take it out and the helicoil comes out too, or falls into the cylinder, or one coil will pop out. You go to put the plug back in and it'll crossthread/not go in/or strip the whole bleeding mess out.

Helicoils






Helicoil fail





Keysert installed.





Keysert installation.





I work on industrial printing presses, print National Geographic, etc. and we won't use a helicoil on anything because once the helicoil fails you have an even bigger hole to repair. If the keysert strips out you just redrill it to the tap size and the keysert threads come right out. Spin in another, set the keys and you're done.

Ideal most effective repair on a spark plug hole in an outboard is replace the head with another good one.

Jamie


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## crazymanme2 (Sep 17, 2010)

If your going to take the head off why not just get it welded up,redrill & tap it out?Just like new!


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## Pappy (Sep 17, 2010)

Last time--------------Just go to NAPA and get the insert kit for the head and be done with it. Some ACE Hardware stores even have the kits. They run from $28 up to $50 for the kit depending on where you buy it. Nice thing about it is that you don't have to drill at all. There is a reamer included with the kit and 3 different length inserts. The inserts are knurled and at the end of the procedure you tap the insert with the tool and hammer to expand the insert into the hole. It is then permanent! You dont need to find a used head although one may be cheaper, go through the expense of taking the head to a machine shop for welding, machining, etc. You have had some good responses here with good information on correct inserts for your application. Do yourself a favor and read some of the profiles on your responders if you are still unsure. An example is that Crazyman appears to be a welder/Millwright so welding would be easy for him (and a good repair) ....not necessarily for you. That should help you make a decision on what is sage advice and what may not be.


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## Hanr3 (Sep 17, 2010)

I'll have to check into those other styles of inserts. Never had any problems with Helicoils. Then again I've never had any real problems with my chevy either, however there are a bunch of people who complain about them too. :mrgreen: 

Sans to say my resume isnt posted on this site. :mrgreen: 

Watch for my trailer update project. I needed new guides, there are advantages to working in a heavy equipment manufacturing plant. :mrgreen:


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## bobberboy (Sep 18, 2010)

Ok. Thanks everyone for the info. I am in no hurry to fix but at least now I have some info. I think I will first do a few searches and see if I can find a new (used) head. That may be the surest fix but I'll see at what cost. Failing that I'll probably try the insert.

Pappy, thanks for your advice but don't get too impatient. There are a lot of guys here who, like me, don't know much about motor repair. I haven't worked on a motor of any kind for a long time - my cars go to the shop where someone who knows how can take care of them. Anyway, I don't think I remember any subject on tinboats where there has been consensus. Usually there are at least a few different approaches to everything and some fit situations better than others. Money, time and skill all come in to play when people decide to try one way or another. My dad once gave me a rather crude kernel of wisdom - "opinions are like a**holes, everybody's got one". Proctology is not among my skills so instead I read, ask questions, sort out the answers and try to learn. 

Thanks again everyone. Once I deal with the above problem I'll try starting the motor and report.


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## Hanr3 (Sep 18, 2010)

There is another option that hasn't been mentioned yet.

JB Weld. 

It wont have any problem handling your spark plug problem. 

Call a few machine shops in your area, they may be able to dril and retap the hole for you at a reasonable cost. Provided you cant find a replacement head.


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