Gearbox oil flush screws are stuck!

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Alexis
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Gearbox oil flush screws are stuck!

Post by Alexis » Mon May 13, 2019 5:57 pm

Hello,

I am trying to change the gearbox oil of my Nissan 9.9 outboard (the last service was probably 4 years ago, but with a very light usage on that period). As I could read everywhere on the internet, it is very common for these screws to get completely stuck and be very hard to extract. They are the regular large slotted head. I tried to move them (the upper and lower one) with a 1/2 screwdriver, I tried to damp overnight with WD40, but nothing worked so far. I am very afraid to deform the heads...

Here are my options:

1. Tapping gently on the side of the screws with a chisel.

2. Heating the screws, though I am nervous about approaching a flame to a gas engine...

3. Drilling and using a screw-extractor. I have never done that before and this makes me quite nervous as well...

4. Going to my dealer with a 30 ft trailer (I don't like that, he won't like it too). I don't want to deal with removing the entire engine and put it in the car, which is going to dip and smell bad. I am also quite nervous of not having my engine in time for the season...

5. Using the engine one more year (after all, there is no sign that anything could be wrong) then removing the whole lower unit at the end of the season for a complete tune-up next winter.

What would you do?

beechkingd
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Re: Gearbox oil flush screws are stuck!

Post by beechkingd » Mon May 13, 2019 7:06 pm

I would try hitting your screw driver with a hammer a few times while trying to turn it. If that doesn't work try heating it with a propane torch for a minute or so and try hitting and turning again. I personally wouldn't worry about a fire, the carbs are a good distance from where the flame would be.

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Jimmyt
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Re: Gearbox oil flush screws are stuck!

Post by Jimmyt » Mon May 13, 2019 7:09 pm

Put a metal drift on the screw head and give it a couple of sharp strikes with a small ball peen hammer. Don't give it a big wind up, just a sharp strike. You don't want to break the casing. After a couple of strikes, try the screwdriver again. You can use a crescent wrench on the blade or shaft ( if its square) for more leverage.

If that won't do it, you can use a chisel or punch to strike the head tangentially in a loosening direction. This will tend to tear up the plug, but may be the only way to get it out.

Oops - basically repeat the above. Oh well, need to type faster I guess.

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Tomfoolery
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Re: Gearbox oil flush screws are stuck!

Post by Tomfoolery » Mon May 13, 2019 7:12 pm

I would probably use a drift pin and shock them a number of times. I’d also put heat on them, but with an electric heat gun, mostly because I don’t have a torch any more. :P

I take it the “1/2 screw driver” is a very large one. I’ve had stuck gear oil screws in the lower leg when I got the boat, and I just put a lot of torque on them with a giant flat screw driver and they popped loose. New gaskets were used after that, of course. I change the lower unit oil every year, as the shaft seal lets a little water in over the season, even with the prop out of the water whenever it’s not driving the boat, and it’s so old and corroded I’m afraid to try prying the seals out as I may have a rough time getting new ones in.

Edit: Looks like Jimmy beat me to it. Drift pin and sharp raps, dead-on to the head.

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Jimmyt
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Re: Gearbox oil flush screws are stuck!

Post by Jimmyt » Mon May 13, 2019 8:38 pm

I was trying to imagine WWTFD... (what would Tomfoolery do)!

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Chinook
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Re: Gearbox oil flush screws are stuck!

Post by Chinook » Mon May 13, 2019 8:42 pm

I would also suggest making sure that your screwdriver precisely fits the slots in the drain plugs. Slippage often occurs because the screw driver isn't the exact right size, or because the edges of the blade have become worn. Touching it up on a grinder to square it off and adjust fit should enable you to put a greater degree of force on the screws.

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Re: Gearbox oil flush screws are stuck!

Post by Estate Sail » Mon May 13, 2019 9:46 pm

my recommendation is to go to a tractor dealership and get the best industrial penetrating oil they have. Keep soaking the drain plug for a couple of days and then try it. Another penetrant option if that doesn't work, is dye penetrant used for non destructive inspections. You can find this online at a place like aircraft tool supply or maybe a mechanic at the local airport will let you borrow a can. then try to remove the screw with a good fitting screwdriver.
Another option if that doesn't work is an impact wrench with a screwdriver blade attached and set at a low power setting.
I would stay away from the easy out option. I am always afraid to break one off. If you do, they are impossible to remove with a drill.
As a last resort, If you have messed up the head and drill it out, be careful to drill smaller that where the threads start and then try and gently chisel out the remaining part of the screw.
Good luck!

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Re: Gearbox oil flush screws are stuck!

Post by kurz » Tue May 14, 2019 8:56 am

I allways use my ratchet. So use the bigest srewriver to put in that fits. Work patiantelly. But at least you will have enough power.

Alexis
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Re: Gearbox oil flush screws are stuck!

Post by Alexis » Tue May 14, 2019 10:18 am

Thank you very much for all your answers! I really appreciate to have so much to read, so soon after posting!

Alexis
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Re: Gearbox oil flush screws are stuck!

Post by Alexis » Tue May 14, 2019 10:54 am

I thought a lot about these screws during the night and decided that the oil HAD to be flushed what ever it takes! As Tomfoolery said, the reason is that even if the seals are still in a correct condition, a little bit of water entered each season. So, oil change it is!

Here is the plan:

First, I am already planning next year service and will purchase hexagonal head screws, which are easier to extract, to replace the actual slotted ones. Then I won't have to mind about saving the existing screws when I take them out.

I will heat up the screws with a blow torch, wait it cools a bit and hit them with a drift pin. (BTW, nice battle Jimmyt and Tomfoolery!)

About the extraction tool: I have a large screwdriver but the screw heads are already a bit messed up and don't have enough grip. I will do my best but I am not sure I will be able to break them free that way... @Kurz: I like the idea of using a ratchet. I am guessing an offset screwdriver could work too?

Here is the second phase (last phase being the use of dynamite): what about drilling in the center of the screw and heat again, to try relieving pressure from the thread?

@Estate Sail: a screw extractor sounds like a good last option. Though, you propose to stay away from it: what would be the risk at that point, if I already drilled and heated that f*#%ing ba#*ard screw anyway?

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Re: Gearbox oil flush screws are stuck!

Post by Jimmyt » Tue May 14, 2019 9:21 pm

Estate Sail has evidently pulled my favorite stunt. You start with a stuck bolt. Drill a hole in it. Insert an easy-out. Then break the hardened easy-out off in the hole in the center of the bolt. Now, you have a hardened material where you really don't need it. You can't drill it out because it's harder than the drill.

When they work, they're great. When they break off in the hole, it can be bad. If you're lucky, it might break off with enough sticking out of the hole to grip it with vice grips and back it out.

Not to put words in his mouth, but that's my thinking.

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Re: Gearbox oil flush screws are stuck!

Post by Alexis » Wed May 15, 2019 1:57 pm

Jimmyt wrote:
Tue May 14, 2019 9:21 pm
Estate Sail has evidently pulled my favorite stunt. You start with a stuck bolt. Drill a hole in it. Insert an easy-out. Then break the hardened easy-out off in the hole in the center of the bolt. Now, you have a hardened material where you really don't need it. You can't drill it out because it's harder than the drill.
I actually discussed with a colleague today who experienced the exact same story on the exhaust manifold of his project car. He told me he had to hire a welder to connect a rod to the extractor bit left in the screw. The conclusion is that you only want to purchase professional brands when in comes to extractors (Home Depot is definitely not an option).

I hope I won't need to use an extractor though. I purchased a torch yesterday, I have new drain plug screws to replace the old ones, I am ready to go! I just need a bit of time!

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Re: Gearbox oil flush screws are stuck!

Post by Tomfoolery » Wed May 15, 2019 2:10 pm

If it were me, I'd gently heat the area around the screw rather than the screw itself. The screw will warm too, but if you work fast, the surrounding metal will expand faster than the screw itself.

However, if the screw is steel, the surrounding aluminium will expand much faster than the steel screw at the same temperature, as the coefficient of thermal expansion of aluminium is about twice that of steel. But I don't know what yours is made of.
Last edited by Tomfoolery on Wed May 15, 2019 2:16 pm, edited 1 time in total.

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Re: Gearbox oil flush screws are stuck!

Post by Tomfoolery » Wed May 15, 2019 2:14 pm

Jimmyt wrote:
Mon May 13, 2019 8:38 pm
I was trying to imagine WWTFD... (what would Tomfoolery do)!
:D :D Well, Tomfoolery would be tempted to just pay someone to make it right, but the last time I did that, they stripped out a hole for a bolt holding the lower leg on, and just filled the hole with caulk while charging me for drilling and inserting a helicoil. Same guys who did the engine survey when I bought it, and I had paid them to replace the impeller so I could be confident in a new (used) purchase. :x

I do everything myself now.

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Re: Gearbox oil flush screws are stuck!

Post by sunshinecoasting » Sun May 19, 2019 4:40 am

I can help here, I just had the same problem with my engine flush screw, I used big square shafted screw drivers with a shifter on the shaft but it wouldn't budge. So I came up with this idea, I used a large perfectly fitting screw driver bit from an impact set, I fitted this in to my AEG cordless screw driver with the clutch up high, fitted the bit in the slot and hit the button, it ratcheted for about 5 seconds then the screw came undone, perfect.

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