Leaking sparkplug threads in 140 v4 and options for fixing it.

[indyfiero]

Model j140tlcos

First a little background. I bought this boat a month ago as a project under the assumption the motor was shot. The seller told me it had blown a piston ring and had low compression. I checked the compressiom before buying and was surprised to find 3 cyl at 125 and one at 115.

One thing i noticed after getting it home was that the top starboard cylinder sparkplug was rethreaded with some kind of insert. Sav a thread or something. Sometimes this insert would come out attatched to the plug and sometimes it would stay in the head.

I knew this wasnt great but figured if it would sometimes bite and stay in the head i would just tighten it up good and leave it be. Turns out it backed itself out of the threads today while i was out on the water and left me stranded, needing a tow.

It also, even when tight, leaks a small amount of oil and gas mix around the threads, telling me its no longer sealing properly.

What are my options here? It looks like, if i can even find one, a cylinder head for this thing is going to cost a fortune brand new. The used ones i see on ebay look like theyve been run over by a lawn mower. Can i find another insert for this thing and try to use the existing threads? Should i take it to a machine shop and let them try to fix it?

 

[oldboat1]

Depends on how handy you are. Ever do a helicoil? Might visit an auto parts store and take a look at a package, and check the instructions. Have difficulty seeing how one would back out, but reviewing installation instructions in light of what you have might help. Otherwise, a shop should be able to handle it for you.

 

[510freak]

You could red loctite the hell out of the sav a thread to help keep it in. As for the sealing issue not sure. You or a machine shop could put a timesert in. They are much better than a helicoil. They actually repair the threads stronger than original seen them used many times in head bolt thread repair

http://www.timesert.com/html/sparkplugAluminum.html

http://youtu.be/pLVDb0xcvMo

 

[fhhuber]

http://www.brillman.com/store/produ...8qGBT7wIh-UTEx7AdkDZOymVjGZfLnW0EuhoC42Hw_wcB

You'll have to look up what oddball larger adapter you need to use to deal with your already somewhat overdrilled (for the save-a-thread or helicoil that is already there) spark plug hole.

oversize drill and tap for an adapter such as this. Red locktite the adapter in place.

Best to pull the head when doing the drilling so you can keep the metal shavings out of the cylinder. Pulling the head on some of these old outboards can be "entertaining" due to the gasket sealing to both the head and block.

Helicoils are temporary and do tend to leak. an actual internal/external thread adapter will be as good a your installation.

Note: The slight "flange" with hex is important. That prevents the adapter from eventually turning on into the cylinder. The "save-a-thread" can end up with most of it doing no good, deep in the cylinder hitting the piston.

 

[Chris1956]

That is a solid insert, right? If so, first clean both the insert and block with acetone. Thread the insert onto the spark plug.Then mix a small amount of marine-tex and apply it to the insert's exterior threads. Now crank the spark plug and insert into the block and let her harden. The insert should be permanently installed into the block.

 

[kenk63]

Depends on how handy you are. Ever do a helicoil? Might visit an auto parts store and take a look at a package, and check the instructions. Have difficulty seeing how one would back out, but reviewing installation instructions in light of what you have might help. Otherwise, a shop should be able to handle it for you.

done this many times with spark plugs both aluminium and cast iron heads, works if done correctly,

 

[indyfiero]

Thanks guys, I'm going to try to track down a replacement insert. If that fails I'll go the loctite or marine-tex route.