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Author Topic: Stripped spark threads on powerhead  (Read 926 times)

June 10, 2018, 12:11:00 PM
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Brendanpd28

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Stripped spark threads on powerhead
« on: June 10, 2018, 12:11:00 PM »
 Rebuild my carburetors and replaced the ignition coils today. Seem to be running much better until a spark plug literally blew right out of the powerhead when test running. I knew it was a little bit stripped but I didn’t think it was that bad!  Can I re-tap these threads? Or is this motor junk now?  I really just can’t catch a break with this motor LOL!! Thanks.
Brendan P. D.

June 10, 2018, 12:36:38 PM
Reply #1

SteelHead

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Re: Stripped spark threads on powerhead
« Reply #1 on: June 10, 2018, 12:36:38 PM »
Brendon , you didn't say what motor you're running but with the info you give , depending on your mechanical skills and budget (you) can fix it . There is a product on the market called Heli-coil that is made just for this issue . If you can take the head off your self and do the repair that's the way, I would go, the repair kit is pricey but any local machine shop can do the job or a auto shop you are familiar and trusting of . You will save a lot of gas money by pulling the head off yourself .The biggest problem would be getting it back together (wiring and such) right . Take pictures and label as you go .Use a little dab of a good anti-seize on the plug threads too.  Good Luck !  :91:   
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June 10, 2018, 12:47:40 PM
Reply #2

Brendanpd28

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Re: Stripped spark threads on powerhead
« Reply #2 on: June 10, 2018, 12:47:40 PM »
Thanks for the tips!! It’s a 1990 Evinrude 88 spl.  Pulling the head should not be much of a problem depending of course how the bolts come out.  I will look into the heli-coil.
Brendan P. D.

June 10, 2018, 02:06:34 PM
Reply #3

Brendanpd28

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Re: Stripped spark threads on powerhead
« Reply #3 on: June 10, 2018, 02:06:34 PM »
I’m seeing a lot of debate on forums about heli-coils vs. time serts. Could I run into any heat transfer issues with my 88 spl using a steel heli-coil? Just want to make sure I do this right the first time! I can’t find anything in my manual about this issue.Thanks!
Brendan P. D.

June 10, 2018, 02:51:08 PM
Reply #4

Brendanpd28

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Re: Stripped spark threads on powerhead
« Reply #4 on: June 10, 2018, 02:51:08 PM »
This is what I’m thinking of going for.....
Brendan P. D.

June 10, 2018, 03:48:59 PM
Reply #5

theFunsmith

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Re: Stripped spark threads on powerhead
« Reply #5 on: June 10, 2018, 03:48:59 PM »
 I have used helicoils on head cover bolts on outboards (going into aluminum head) before with good results. I hadn't seen the time-serts until I read about them here. I took a look at them and am kind of impressed really. They look like they do offer a benefit over the helicoil in sealing potential, and it wont have the tab like the helicoil running through the center of the coil (used for installation) and won't interfere with the end of the spark plug. I think a spark plug may be one excellent spot to go with the time-sert. I would recommend whatever method you choose to repair it, that you remove the head to do the repair and put a new head gasket on upon reassembly. No good can come from introducing the metal chips into the cylinder should you try to repair it in place.

June 10, 2018, 07:12:26 PM
Reply #6

Brendanpd28

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Re: Stripped spark threads on powerhead
« Reply #6 on: June 10, 2018, 07:12:26 PM »
Thanks Funsmith! Heli-coils seems pretty straight forward and looks as if they have been used for my application many times. I was just concerned about the dissimilar metals regarding heat transfer. I don’t know enough about time-serts but will research further. I was contemplating doing the repair in place using grease to catch the shavings especially since they mainly come outward when inserting the tap, but I agree it’s not worth the risk. If it’s as simple as pulling the cylind head and installing a new head gasket then I’ll play it safe and do that. I’ll just pray that the old retaining bolts budge since they haven’t been removed in 28 years lol!! Thanks!
Brendan P. D.

June 10, 2018, 11:22:27 PM
Reply #7

theFunsmith

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Re: Stripped spark threads on powerhead
« Reply #7 on: June 10, 2018, 11:22:27 PM »
You may have no trouble at all, but a good soak with penetrating oil on the head bolts can't hurt. I have seen induction bolt heaters as well that seem to work well If there is any corrosion around the bolts that prevents easy removal. I don't know if they are rentable, but a you might talk somebody at a shop into zapping the head bolts for you if they are giving you trouble. There are several styles of induction bolt heaters, there were certainly a few times I wish I would have known about this method.

https://www.youtube.com/watch?v=YJElT9xK3bk

If it were me, I would look hard at the time-serts. After watching some videos, it looks like Ford techs use them in their repairs of  the aluminum factory heads when their spark plug threads let go.


June 14, 2018, 10:54:39 AM
Reply #8

Brendanpd28

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Re: Stripped spark threads on powerhead
« Reply #8 on: June 14, 2018, 10:54:39 AM »
Update:   Found a parts motor for Cheap money. Going to use the cylinder head and one of the carburetor float bowls off of that instead of ordering a new bowl and using a heli-coil.  Got the cylinder head off today.... all bolts came out with ease thankfully! I snapped a couple pictures of the cylinders, a little bit a scoring it looks like but I have about 90 to 95 PSI on all four cylinders. I figured that was relatively decent for such an old motor. Anybody see anything I should be concerned with here? Thanks!
Brendan P. D.

June 14, 2018, 01:33:59 PM
Reply #9

wingtime

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Re: Stripped spark threads on powerhead
« Reply #9 on: June 14, 2018, 01:33:59 PM »
Those cylinders look great.  You can still see the cross hatching from when they were honed.  Depending on what gasket you have OMC used a special non hardening sealing compound on the gaskets.  Make sure you get the torque specs on the head bolts and torque them in sequence.  You usually torque them in stages... not the full torque on the first pass.  Also use the OMC sealing compound or marine grease on the bolts so they don't stick in the future.  Also the bolts need to be re-torqued after about 20 hours.


As for the taping the spark plug hole on the motor.  Not a big deal just use lots of grease on the drill/tap to catch any metal shavings.  or just run a shop vac with the nozzle right on the hole as you tap it.
1998 Explorer w/ Etec 250


1987 170 w/ Evinrude 90

June 14, 2018, 02:12:01 PM
Reply #10

Brendanpd28

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Re: Stripped spark threads on powerhead
« Reply #10 on: June 14, 2018, 02:12:01 PM »
 Thanks wing time!  I am just taking another cylinder head from a parts motor to swap it out instead of drilling and tapping. Felt like the best route to go.  I am currently trying to figure out how the water passages work around the cylinder for my own education. There’s a gasket that separates the face plate of the cylinder head  from the cylinder head itself. The picture below makes it look like the Deepwater passages on the cylinder head are all clogged up but that’s mainly just the gasket still on there. But the smaller passages on the face plate we’re pretty much full of gunk and grime. Interesting since I haven’t had any overheating issues other than the instance at the very beginning of the season.  Makes me want to pull off the Portside cylinder in inspect while I’m at it Lol!
Brendan P. D.

June 14, 2018, 04:02:16 PM
Reply #11

theFunsmith

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Re: Stripped spark threads on powerhead
« Reply #11 on: June 14, 2018, 04:02:16 PM »
She does look due for some kind of flush. Glad you got it figured out. There is no band-aid fix as good as repairing with oem parts when you can.

June 15, 2018, 02:22:49 PM
Reply #12

wingtime

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Re: Stripped spark threads on powerhead
« Reply #12 on: June 15, 2018, 02:22:49 PM »
I'd absolutely pull the water jacket cover off the other head.  This is why you need to use something to flush these motors if they are used in salt water.  Salt away, salt terminator vinegar. Etc etc.  See if you have a local outboard rebuilder that can hot tank or media blast those heads for you.  Now is the time to do it while they are off in  your hands.  At the very least soak them in hot water with vinegar or greased lightening.
1998 Explorer w/ Etec 250


1987 170 w/ Evinrude 90

June 18, 2018, 01:44:41 PM
Reply #13

Brendanpd28

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Re: Stripped spark threads on powerhead
« Reply #13 on: June 18, 2018, 01:44:41 PM »
Update:  local outboard mechanic gave me this cylinder head to swap onto my motor.  Looking at the condition of the interior I would say this is absolutely a no go. He is claiming that all of the mating surfaces are all  that matters and they are in good shape.   Does anybody think some of these gouges can be cleaned up a bit in the cylinder head will not create any issues with my Pistons if the mating surfaces are in great shape?  I am very uneasy about putting this on my motor in its current condition  but I am not a powerhead expert. Thanks!
Brendan P. D.

June 18, 2018, 02:32:22 PM
Reply #14

Capt. Bob

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Re: Stripped spark threads on powerhead
« Reply #14 on: June 18, 2018, 02:32:22 PM »
Flip over the cylinder head in the photo that is shown 4 posts back (I believe you took that off your motor :ScrChin:).

How do they compare?
]
Capt. Bob
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