Stripped Spark Plug Hole?

[Yellowstone]

So, long story short, per my other post, I believe I have my JW-10 running great after lots of great advice here and on FB group. I did everything the right way versus the OK way from what I can tell, using the coil locating ring and timing tool and reworking the carb settings a bit. I even got it to stop leaking/dribbling gas. Problem is after about 10-15 seconds of running great, it died, and I noticed the back spark plug popped out. The hole is stripped. I had carefully and slowly torqued them in at the recommended 20 foot pounds. Should I just be hand tightening them versus what the service tech manual says?

Anyway, what would you suggest? I started looking for a replacement head and know I should be a new gasket on if I go this route. The cheapest one I saw on ebay was $75. I also see there are replacement thread kits available. Have you or would you ever go this route? I know another options is to see if you can find a parts motor. One was available for $20 recently that I could have/should have bought. Going to check with my neighbor too who’s wife supposedly has some of these same motors lying around his shed. Thanks!

[drifter]

I have done this repair several times using a thread repair kit which consists of a reamer/tap and 14mm thread inserts. Got mine off of Ebay for around $8 but many auto parts stores carry them for around $15. They worked extremely well for me . Simple and quick.

[squierka39]

For $75 you should get a whole JW for that. Heads at our swaps go for around $10. Try the want ads here. If you haven’t joined yet, join up, go to a swap meet. Someone might even give you a JW head. Also, yes the thread kits work fine.

[Mumbles]

To repair the stripped threads properly, you must use inserts designed for spark plug threads, not the regular wound wire inserts used for general thread repair shown in the third photo. The proper inserts get swaged into place with a bit of red hi-temp silicone on them.

[bobw]

Mumbles is correct about the type of thread inserts you have to use for this repair. I used one of these on a stripped plug on a ’72 Evinrude 25hp and it worked perfectly. As an alternative, here’s a link to a list of parts for 1955 Evinrude and Johnson 3HP. They have a used cylinder head for $10 and I believe it will fit your 1954 model.

https://thebrazilianconnection.com/55e3parts.html

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[olcah]

I also have stripped plug threads in a head. I believe the OMC recommendation of 20 FTlb is just WRONG. Now I put plugs in by feel and use a short wrench for a lot less less torque.

What is experience of others?

• This reply was modified 4 years, 7 months ago by olcah.

[Yellowstone]

Thanks guys. Wow, my original post was all over the place. A bit rushed on the way to church this morning. Anyway, I may try the replace thread using the plug-specific kits you recommend. In doing more research online, is it recommended to pull the head off? If so, I know I am supposed to put a new gasket on. Would like to avoid doing that if possible. But would rather do it the right way. Thanks.

[bobw]

Some folks might put grease on the tap to catch any metal shavings, but I would pull the head off.

Olcah – yes, I think 20ft-lb on the plug torque is too much. I got to 16 at the most or 1/2 turn of the plug after the plug gasket seats against the head when turning by hand.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[Yellowstone]

Ok, I see the helicoil kit is $22 on amazon. Looks like cheaper ones out there but mixed reviews. That with the price of the new gasket, I may just buy a new head then IF I can find one for less than the kit. My wife asked me again, WHY did you pull this thing apart when it ran? I don’t get it? I started to explain how one cylinder was shot, and the other not good and she’s like, wait, wait, I don’t need to know. Just forget it. Haha. BTW, I was encouraged to see the water pump peeing water nicely. Before I replaced it you had to put your hand under it to tell if anything was coming out.

This engine and new hobby has taught me a lot so far. We have a 25 year old Larson runabout in beautiful condition with a 115 HP Yamaha that I bought 5 years ago to take the kids tubing. All I’ve ever done to it is make sure it has plenty of Yamalube in the blend tank. Just the other day I was thinking, geez, I probably should have replaced the gear lube several years ago at least.

[amuller]

Helicoil thread inserts work fine if properly installed. Sometimes they are used on new motors. I would take the head off. If you do it carefully you should be able to save the gasket. But if the head bolts don’t want to move, you can grease up the tap to catch chips and probably be OK.

But these heads should be easy to find. Disregard ripoff ebay prices. You can lap them flat if you have something that can serve as a surface plate. Piece of plate glass, or even a table saw table is likely good enough.

IMHO, contrary to a lot of official advice, it is often safer to tighten plugs by feel. Especially if using anti-seize that may have a low coefficient of friction. And torque wrenches have their own issues, such as the pointer hanging up so you keep on pulling. Of course, a new plug will have a new crush-type gasket and so the feel of the first tightening will be different.

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