Gear drain screw/frozen in/tap/replacement

[bluegothic13]

Hi,

I have a 1986 125HP Force OB. She still runs like a kitten. However, the gear oil drain screw at the bottom of the leg is frozen in. Previous owner jammed in a hex head screw that's stripped.

I plan to drill out the screw, tap new threads, and put in a new drain screw.

I'm going to need a bigger size screw than the original one.

Can any one tell me how big is the original screw is and where I could get a bigger screw?

And am I crazy to do it this way? Is the leg aluminum and will I inflict damage drilling out a metal screw?

Thanks.

 

[Frank Acampora]

Re: Gear drain screw/frozen in/tap/replacement

Some of those engines originally came with a 1/4 X20, recessed hex, set screw. They frequently corrode in and are very difficult to get out.

One trick I try before drilling is to hammer in a slightly larger Torx bit (1/4 inch drive). It grabs better than a hex wrench. And, if you can drain the unit by pulling off the prop, removing the anode, and removing the lowest of the four bolts holding the spool in, then you can apply heat with a propane torch--aluminum expands way faster than the steel screw. You WILL bugger-up the Torx bit so buy a cheap set.

If you find that you need to drill it, there is plenty of metal there; some engines came with a 1/8 NPT (National Pipe Thread) plug and some came with a 3/8 plug just like the fill and vent screws. You can even go as high as 1/2 NPT but it is best to use the smallest plug you can.

Because NPT taps and plugs are tapered, do not tap too deep or the plug will not seal. Tap a little way in and try the plug, tightening fairly snugly with the wrench. If it sticks out too far, tap a little further. You should be able to find a recessed hex, stainless NPT plug However, Chrysler/Force made a slotted head NPT 1/8 inch plug. Mind you: 1/8 is the inside diameter of pipe. the actual plug is slightly larger than 3/8 inch.

Whatever you end up doing, use anti-seize or teflon tape on the plug so it comes out easier next time.

 

[bluegothic13]

Re: Gear drain screw/frozen in/tap/replacement

Hi Frank,

A thousand thanks for you imput. I will try your suggestions.

+Jay