How to remove stuck drain screw on Mariner 2M

[conks01]

Hi,

The top gearbox oil drain plug screw on my 1984 Mariner 2M 6A1 2hp outboard will not budge!

I've used penetrating Oil on it, a heat gun, and tapped it with a hammer, but it's being rather stubborn!

Does anyone have any advice what else I can try please? I'll keep with the penetrating Oil over the next few days but it seems pretty stuck!


Many thanks.

 

[Fr J Hackett]

Try a mechanical impact driver with a good fitting screwdriver blade.

 

[Martin_J]

Boiling water, slowly poured over it.. A few kettle fulls throughout the day over about a week..

Don't rush it..

 

[Wansworth]

good fitting screw driver with molegrips on shaft.....refering to its parentage could help

 

[billyfish]

Impact driver, with it laid on its side on a hard surface

 

[ChromeDome]

"Good fitting" is the key word.

Maybe support the screw driver by strong grip water pump pliers on the screw hear outside.

 

[Fr J Hackett]

"Good fitting" is the key word.

Maybe support the screw driver by strong grip water pump pliers on the screw hear outside.

Just using a screwdriver and whatever to turn it relies on the torque ie leverage you can obtain an impact driver will exceed what can be obtained by screwdriver and lever.
All mechanical impact drivers have a selection of bits and there will be a snug fitting one that will do the job

 

[Daydream believer]

Put a large screwdriver bit in a carpenters brace. Lean on it really hard with it in your stomach & rotate the brace. You can apply a lot of weight when pushing in to the slot if you get over it & push down. Then a lot of power on the brace.
Even a bit of metal, like a bit of a plate washer cut down in half, can be put in the brace, if it fits in the slot as you only want to break the seal.

 

[Seashoreman]

No one mentioned a hot air gun? As well as an impact screwdriver of coarse.
I have released 100 year old woodscrews with the heat from a soldering iron.

 

[conks01]

Thanks all. After more penetrating oil, and the help of a mate who conveniently popped round to catch up, managed to crack it open. Now for the impeller....

 

[ean_p]

You could always get some smallish (8-10 inch) Stillsons and lock onto the side of the head but failing that then I'd also think of the impact driver but a powered one not one of the sh*te 'hammer' types which will more than likely crack the casing before moving the screw..........

 

[penberth3]

Thanks all. After more penetrating oil, and the help of a mate who conveniently popped round to catch up, managed to crack it open. Now for the impeller....

That's good. Another tip for the future, try tightening before you unscrew. Only a little bit, with a bit of gentle impact. That can break the bond without damaging the head in the "unscrew" direction,

 

[john_morris_uk]

… but failing that then I'd also think of the impact driver but a powered one not one of the sh*te 'hammer' types which will more than likely crack the casing before moving the screw..........

Au contraire. I have powered impact drivers snd imoscf drivers you hit with a hammer. The problem with the powered one is keeping the bit in the slot. With the hammer type you can position carefully and control your hit impact. No contest for reluctant screws.

The powered one is brilliant for driving sockets and I wouldn’t be without it. And yes it’s got a whole range of power settings before anyone asks.

 

[ean_p]

Au contraire. I have powered impact drivers snd imoscf drivers you hit with a hammer. The problem with the powered one is keeping the bit in the slot. With the hammer type you can position carefully and control your hit impact. No contest for reluctant screws.

The powered one is brilliant for driving sockets and I wouldn’t be without it. And yes it’s got a whole range of power settings before anyone asks.

One of these John?



Then we'll have to agree to disagree.......I've destroyed more of those with an hammer then they have released fixings for me....... ! I never contemplate there use anymore and probably haven't for better than 20 years or more....!

 

[john_morris_uk]

One of these John?

View attachment 173642

Then we'll have to agree to disagree.......I've destroyed more of those with an hammer then they have released fixings for me....... ! I never contemplate there use anymore and probably haven't for better than 20 years or more....!

We will definitely agree to disagree. Used carefully I’ve removed many a recalcitrant screw with an impact driver just like that. Hold it firmly and twist in the direction that you’re trying to unscrew is how I’ve been taught. (Assuming you’ve set it to the right direction in the first place!)

I’ve tried using my Makita impact 1/2” drive wrench with an adapter and screw driver bit and no matter how hard I try and steady it and whatever power setting I use and no matter how gently I squeeze the trigger (it’s variable speed) the thing very quickly jumps out of the slot. It’s a fantastic tool but not for undoing corroded or jambed screws. It’s great for leaving score marks across the casing with whatever screw driver bit you’ve got in it though.

 

[Mark in Portishead]

That's good. Another tip for the future, try tightening before you unscrew. Only a little bit, with a bit of gentle impact. That can break the bond without damaging the head in the "unscrew" direction,

That's a very useful tip which I have also used on several occasions with success. Sometimes, once the screw is starting to move, it pays to repeatedly untighten and re-tighten, each time unwinding a few degree further.

This looks like a steel screw in aluminium. If so, I guess this may be a galvanic corrosion issue and some protection on the threads during refitment might benefit.

 

[Daydream believer]

One of these John?

View attachment 173642

Then we'll have to agree to disagree.......I've destroyed more of those with an hammer then they have released fixings for me....... ! I never contemplate there use anymore and probably haven't for better than 20 years or more....!

I have had one of those for 60 years. When I hold it in my left hand my little finger always overlaps the bit that closes up. So when I belt it, it nips the skin of my finger & I get a 20mm long cut. . If I hold the b..y thing higher up, my hand sticks out the top & I belt the forefinger with the club hammer. If I do not grip it tight it does not work. Gets used about once every 5 years & I know exactly where to find it,-- in its little tin box.
I have probably thrown more F's at that tool- per use -than any other.

 

[Rappey]

, I guess this may be a galvanic corrosion issue and some protection on the threads during refitment might benefit

The threads are usually wet with gear oil. The copper washer is mated to aluminium and stainless steel and probably overtightened and often submerged. A good thump often breaks the seal.
The issue with a cordless impact driver on some bolts or screws when they are seized is it just shears the heads off.

 

[Mark-1]

One of these John?

View attachment 173642

Then we'll have to agree to disagree.......I've destroyed more of those with an hammer then they have released fixings for me....... ! I never contemplate there use anymore and probably haven't for better than 20 years or more....!

That's weird, on the few occasions I've used them they've been miraculous. Certainly not 100pc effective but certainly the first think to try. (I've never tried the other kind.)


EDIT: @conks I'm enjoying your posts, thanks. I see a project outboard in my future. Like the old duffers with stationary engines except an outboard has a practical purpose.

 

[MontyMariner]

I never know which way to twist the head for tighten / loosen on these.
An easy way to remember would be helpful.
The powered ones are great.