250 HP 4 stroke 2007 need thread size for Oil drain Bolt

[boscoe99]

It might have taken over 150 pound feet of torque to intentionally strip the threads. It was a struggle even using a breaker bar. Even though most folks that don't use a torque wrench will over tighten fasteners, I can't see anyone ever coming anywhere close to mechanically breaking perfectly good threads on a Yamaha outboard motor drain pan.

Which is why my hypothesis is that over time, given sufficient tightening and un-tightening cycles, the aluminum threads crack and break. Those are cut threads I believe. Not rolled threads. Cut threads are more susceptible to cracking at the root of the thread. Everything is fine until one day it is not.

Maybe.

[robert graham]

It almost has to be a cross-thread problem....how many folks are going to put enough muscle on a drain plug to rip the threads out???

[Capt.Terry]

Once I am done with this, it is time to get that dipstick oil sucker ...
I almost had the Helix coil today got a M14 x 1.5 coil , and the tap was a 14 however I looked at it hard and it was a 14 UNC not the same pitch and I just couldn't find a 9/16" drill bit.. so it looks to be an Amazon or Ebay search to get one reasonable. I think I'll leave the tab on, unless I feel reel good and can get at it with a good needle nose but, why, If I get the coil in and the bolt fits flat. I don't intend to use this port. I almost thought to just fill it in with some epoxy. but that can be a last resort --- a lot of thank you's out to you all for the help. all these blunders become good learning skills. What is the Phrase "too soon we grow to old and too old we grow too smart" > cheers guys.. see you on the water > I hope

[rodbolt17]

typically the thread damage is done on removal. the AL tends to gall to the SS and its done.
that is also why unless absolutely nessasary I don't remove the plug.
I am good at heli coiling them.
I have a special made tap for the F115-150 motors.
grease the drill, grease the tap. flush with kerosene when done.

[boscoe99]

Hmmm. I had not thought about galling. Could certainly be the case.

[panasonic]

typically the thread damage is done on removal. the AL tends to gall to the SS and its done.that is also why unless absolutely nessasary I don't remove the plug.
I am good at heli coiling them.
I have a special made tap for the F115-150 motors.
grease the drill, grease the tap. flush with kerosene when done.

Rodbolt hit the nail on the head, only slight galling from stainless steel fasteners will tear the aluminum threads to pieces in short order.

Bosceo I have seen lots of threads crack and jam up on the fastener from repeated tightening and loosening cycles...thus stripped out holes. BUT this I find is generally in hard aluminum such as 7075-T6, 2024-T6, 6061..ect Marine grade aluminum is generally much softer and tends to gall and stretch instead of cracking.

Not many bolt holes on A/C that you simply screw a bolt directly into aluminum threads. They are mostly all heli-coiled right from the factory to begin with...which is stronger and much easier to repair. There are hundreds of helicoils on just one engine alone....mostly in the magnesium cases.

I am sick of fooling with helicoils...

I also agree with Townsends on the torque being to high in the first place....I lock wire my oil plug on my bike..don't ask why. I just do.

[panasonic]

Once I am done with this, it is time to get that dipstick oil sucker ...
I almost had the Helix coil today got a M14 x 1.5 coil , and the tap was a 14 however I looked at it hard and it was a 14 UNC not the same pitch and I just couldn't find a 9/16" drill bit.. so it looks to be an Amazon or Ebay search to get one reasonable. I think I'll leave the tab on, unless I feel reel good and can get at it with a good needle nose but, why, If I get the coil in and the bolt fits flat. I don't intend to use this port. I almost thought to just fill it in with some epoxy. but that can be a last resort --- a lot of thank you's out to you all for the help. all these blunders become good learning skills. What is the Phrase "too soon we grow to old and too old we grow too smart" > cheers guys.. see you on the water > I hope

Capt Terry,

You realize you will need a "helicoil tap" and the corresponding tap drill. They are not the same a standard tap....

You should be able to find a helicoil KIT on eBay or amazon that will include the proper tap, drill bit, insert tool and a few coils.

[oldmako69]

All this yammering about TQ is fascinating.

Allow me to derail the thread, but ever so slightly.

My (new to me at 125 hour, 2005 F225 engines) now have about 250 hours on them. This spring while replacing the zinc's I decided to pull the spark plugs and take a look. Every single plug took two hands and a ton of ass to break free from the heads.

While not Andre the Giant, I am 6'3 and 240 and still reasonably fit (strong)for a worn out old man. They were so damn tight that I would have used my breaker bar, had it been in my truck. I've removed large brake caliper and suspension bolts on trucks that popped free with much less torque.

In 40 years of messing with cars and boats, I have never been so fearful about pulling plugs. I have to assume that they were factory installed with such low hours on the engines. Fortunately, I got them all out, and they all looked fine.

But what the hell?

I put them back in with the same amount of force that I have always used on aluminum heads, which is to say, not much. I did not use a T wrench.

Back to your regularly scheduled programming.

[TownsendsFJR1300]

I lock wire my oil plug on my bike..don't ask why. I just do.

Same here, safety wire...

[panasonic]

All this yammering about TQ is fascinating.

Allow me to derail the thread, but ever so slightly.

My (new to me at 125 hour, 2005 F225 engines) now have about 250 hours on them. This spring while replacing the zinc's I decided to pull the spark plugs and take a look. Every single plug took two hands and a ton of ass to break free from the heads.

While not Andre the Giant, I am 6'3 and 240 and still reasonably fit (strong)for a worn out old man. They were so damn tight that I would have used my breaker bar, had it been in my truck. I've removed large brake caliper and suspension bolts on trucks that popped free with much less torque.

In 40 years of messing with cars and boats, I have never been so fearful about pulling plugs. I have to assume that they were factory installed with such low hours on the engines. Fortunately, I got them all out, and they all looked fine.

But what the hell?

I put them back in with the same amount of force that I have always used on aluminum heads, which is to say, not much. I did not use a T wrench.

Back to your regularly scheduled programming.

Mako, where the plugs you took out have very dry threads? I use a lube specifically designed for plugs in aluminum threads, although I can not remember the name of it right now. It is a stick, sort of like a grease pencil, and just a little bit on the threads and no more stuck plugs.

Having the engine warmed up before removing the plugs helps them come out much easier as well.

I have never used a torque wrench to install a spark plug either...

[pstephens46]

All this yammering about TQ is fascinating.

Allow me to derail the thread, but ever so slightly.

My (new to me at 125 hour, 2005 F225 engines) now have about 250 hours on them. This spring while replacing the zinc's I decided to pull the spark plugs and take a look. Every single plug took two hands and a ton of ass to break free from the heads.

While not Andre the Giant, I am 6'3 and 240 and still reasonably fit (strong)for a worn out old man. They were so damn tight that I would have used my breaker bar, had it been in my truck. I've removed large brake caliper and suspension bolts on trucks that popped free with much less torque.

In 40 years of messing with cars and boats, I have never been so fearful about pulling plugs. I have to assume that they were factory installed with such low hours on the engines. Fortunately, I got them all out, and they all looked fine.

But what the hell?

I put them back in with the same amount of force that I have always used on aluminum heads, which is to say, not much. I did not use a T wrench.

Back to your regularly scheduled programming.

Betting someone other than factory did that bit of nonsense. My boat had 240 hours so I assume they were replaced at least once before me.

Rodbolt has probably broken the factory seal on a few spark plugs in his time. Wonder if any were as tight as yours?

[oldmako69]

They have 240 on them now, but I pulled the plugs at probably 180-190.

Threads were dry as a bone. Tips smoke grey and uniform across all 12.

THIN coat of anti-seize on the threads and hand tight on the way back in.

***I had a plug blow out of a head once. Car was a 99 Infiniti Q45 with aluminum heads. I had replaced the plugs about 60-80,000 miles prior, but that's a guess. They were supposed to be 100K plugs.

At any rate, driving down the interstate the car instantly develops a hell of a miss. I am about 2 miles from my exit, and its 0400 and I gotta pee. The car has over 200K on it an owes me nothing at this point. So, I slow down and limp home.

Pop the hood the next day and the damn plug is just laying there, still connected to the coil. The tip of it looks like hell.

I buy a new plug. It won't thread in. I think the old one just got loose and slowly unscrewed itself. These are plugs with LOTS of thread, almost an inch. What I figure is that the compression pop at each ign cycle acted like a hammer on the bottom of that plug. And, over time that hammering ruined the threads in the alum head as it banged on the plug. Just ripped them all to hell.

This is one hell of a complicated engine with acres of plumbing and electronic connectors and crap across the top of it. All of which is now probably about 13 years old and has gone through several thousand heat cycles. NO WAY I was going to pull all that crap without breaking half of it in the process. And, the parts prices were insane. Plus, what else am I going to find in there when I get the head off?

So, I cut new threads and stuck a helicoil in there. I brought the piston to TDC and jammed a kleenex into the hole. Then I took the tap and filled the flutes with vaseline. I cut just enough to feel confident that the tap would find its way back into what I had just cut if I removed it. I then backed out the tap and cleaned all the metal out of the flutes. I Re-vaselined and re-cut. This I repeated several times until I had the bore cut. When I peeked into the bore I could see some very small bits of metal on top of the kleenex.

I took a pencil and jammed the eraser into the vaseline and then jammed this into the bore and gently pressed it into the kleenex. Pulled it out, wiped off the metal and repeated. Did this till there was no metal. Used a dental pic and worked on the kleenex till it came out. Pretty darn sure I got all of it.

Threaded the new 100K plug in and drove that car for anther 50K before I finally donated it to the local PBS radio station. Worked good, lasted a long time.

[panasonic]

They have 240 on them now, but I pulled the plugs at probably 180-190.

Threads were dry as a bone. Tips smoke grey and uniform across all 12.

THIN coat of anti-seize on the threads and hand tight on the way back in.

***I had a plug blow out of a head once. Car was a 99 Infiniti Q45 with aluminum heads. I had replaced the plugs about 60-80,000 miles prior, but that's a guess. They were supposed to be 100K plugs.

At any rate, driving down the interstate the car instantly develops a hell of a miss. I am about 2 miles from my exit, and its 0400 and I gotta pee. The car has over 200K on it an owes me nothing at this point. So, I slow down and limp home.

Pop the hood the next day and the damn plug is just laying there, still connected to the coil. The tip of it looks like hell.

I buy a new plug. It won't thread in. I think the old one just got loose and slowly unscrewed itself. These are plugs with LOTS of thread, almost an inch. What I figure is that the compression pop at each ign cycle acted like a hammer on the bottom of that plug. And, over time that hammering ruined the threads in the alum head as it banged on the plug. Just ripped them all to hell.

This is one hell of a complicated engine with acres of plumbing and electronic connectors and crap across the top of it. All of which is now probably about 13 years old and has gone through several thousand heat cycles. NO WAY I was going to pull all that crap without breaking half of it in the process. And, the parts prices were insane. Plus, what else am I going to find in there when I get the head off?

So, I cut new threads and stuck a helicoil in there. I brought the piston to TDC and jammed a kleenex into the hole. Then I took the tap and filled the flutes with vaseline. I cut just enough to feel confident that the tap would find its way back into what I had just cut if I removed it. I then backed out the tap and cleaned all the metal out of the flutes. I Re-vaselined and re-cut. This I repeated several times until I had the bore cut. When I peeked into the bore I could see some very small bits of metal on top of the kleenex.

I took a pencil and jammed the eraser into the vaseline and then jammed this into the bore and gently pressed it into the kleenex. Pulled it out, wiped off the metal and repeated. Did this till there was no metal. Used a dental pic and worked on the kleenex till it came out. Pretty darn sure I got all of it.

Threaded the new 100K plug in and drove that car for anther 50K before I finally donated it to the local PBS radio station. Worked good, lasted a long time.

That's a good lesson on how to heli coil a spark plug hole in situ...for those who don't know how...

[pstephens46]

They have 240 on them now, but I pulled the plugs at probably 180-190.

Threads were dry as a bone. Tips smoke grey and uniform across all 12.

THIN coat of anti-seize on the threads and hand tight on the way back in.

***I had a plug blow out of a head once. Car was a 99 Infiniti Q45 with aluminum heads. I had replaced the plugs about 60-80,000 miles prior, but that's a guess. They were supposed to be 100K plugs.

At any rate, driving down the interstate the car instantly develops a hell of a miss. I am about 2 miles from my exit, and its 0400 and I gotta pee. The car has over 200K on it an owes me nothing at this point. So, I slow down and limp home.

Pop the hood the next day and the damn plug is just laying there, still connected to the coil. The tip of it looks like hell.

I buy a new plug. It won't thread in. I think the old one just got loose and slowly unscrewed itself. These are plugs with LOTS of thread, almost an inch. What I figure is that the compression pop at each ign cycle acted like a hammer on the bottom of that plug. And, over time that hammering ruined the threads in the alum head as it banged on the plug. Just ripped them all to hell.

This is one hell of a complicated engine with acres of plumbing and electronic connectors and crap across the top of it. All of which is now probably about 13 years old and has gone through several thousand heat cycles. NO WAY I was going to pull all that crap without breaking half of it in the process. And, the parts prices were insane. Plus, what else am I going to find in there when I get the head off?

So, I cut new threads and stuck a helicoil in there. I brought the piston to TDC and jammed a kleenex into the hole. Then I took the tap and filled the flutes with vaseline. I cut just enough to feel confident that the tap would find its way back into what I had just cut if I removed it. I then backed out the tap and cleaned all the metal out of the flutes. I Re-vaselined and re-cut. This I repeated several times until I had the bore cut. When I peeked into the bore I could see some very small bits of metal on top of the kleenex.

I took a pencil and jammed the eraser into the vaseline and then jammed this into the bore and gently pressed it into the kleenex. Pulled it out, wiped off the metal and repeated. Did this till there was no metal. Used a dental pic and worked on the kleenex till it came out. Pretty darn sure I got all of it.

Threaded the new 100K plug in and drove that car for anther 50K before I finally donated it to the local PBS radio station. Worked good, lasted a long time.

That's some Macgyver tactics.......

Can you drill/fill teeth too?

I never used anti seize stuff. Never read that I had too. Maybe I should. Maybe I shouldn't. Townsend posted something showing NGK recommending nothing as I recall.

Sometimes I follow directions. Sometimes I don't. Roscoe gets angry if we don't follow directions.

[oldmako69]

As I understand it, the primary reason behind NOT using anti-seize is that it throws off the TQ readings when reinstalling plugs with a TW. Well, I don't. So therefore it doesn't.

Obviously, getting sloppy and getting the stuff on the electrode will create havoc with the spark. As mentioned, I use it very sparingly and carefully only on the threads. Some do, some don't. I do.

To me, the threat of screwing the threads up in that soft head up far outweighs the chance of incurring ignition problems because of it. But I must say, since that episode with the blown out plug, I do give them just an RCH more oomph when installing them now. My concern is that I didn't put that plug in tight enough.

I'm sure that someone will come up with evidence to the contrary with regard to anti-seize and I am all ears. But when I have to go full Cro-Mag in an attempt to remove ALL 12 plugs on a pair of $35K engines (with heads almost as soft as my junk)...I'm going to use it. Pulling those plugs really had me worried.