1988 force gear oil drain plug stripped

[khoonie]

The drain plug for my lower unit gear oil is stripped. If I drill it out, and then retap it for a new bolt, are there any suggestions for the replacement bolt? What type of head should it have to make a good seal? I was thinking of using a stainless steel bolt with a head that angles (for flush seating) and a nylon washer or o-ring. Can anyone help me on this, please?

 

[pecheux]

Had that happening on my Force OB. Took it to our local Mercury dealer and they installed something called a "helicoil" in the LU . total cost = $ 28.00

Hope that helps.

 

[Frank Acampora]

Well, it really depends upon which drain plug the lower unit has and where it is located.
1. If it is a 5/16 Allen head set screw, under the nose bullet, you can drill out to 3/8 and spot face for a regular drain plug and gasket. You can also re-tap to 1/8 NPT and use a brass or stainless pipe plug. In fact, there is so much aluminum there that you can also drill and tap to 1/4 NPT.

If it is already a standard drain plug on the side of the bullet, you have no real choice but to re-tap to 1/8 NPT or larger. When tapping NPT threads, be aware that they are tapered as is the pipe plug (for sealing) and if you tap too deeply, the plug may not fit properly or seal correctly.

If it is the slotted stainless 1/8 NPT pipe plug under the bullet nose, you again have no choice but to re-tap to 1/4 NPT.

 

[khoonie]

Thanks for the feedback. My LU has the 5/16 Allen head set screw under the nose bullet. I am still carefully step-drilling to see if I can save the threads. If I decide to retap it to 1/8 or 1/4 NPT - which would you recommend? Also, where would I find the drain plugs? Automotive stores or general hardware? Or would I have to order them?

 

[Frank Acampora]

1/8 NPT would be the first choice. These pipe plugs are usually only carried in big box stores and hardware stores in galvanized or if you are lucky, brass. However, they are almost always square topped and thus will stick out. You should be able to order a stainless Allen head pipe plug (like your current set screw) through Fastenal, Graingers, or McMaster-Carr. You can salvage a slotted head 1/8 NPT stainless pipe plug from an old Chrysler or Force head but they are difficult to remove and the slot usually gets buggered.

I doubt you will be able to salvage the threads by step drilling. You will most likely damage the seat at the bottom and the new set screw will not seal.

 

[Frank Acampora]

In fact, if you have not already drilled through the plug, it is not absolutely necessary to drill it at all! If you remove the propeller and anode, then remove one or two of the lower bolts holding in the spool, oil will drain out of the holes. Not as fast as the real drain, but about 90% will drain out. If you loosen all four bolts and rotate the spool so one bolt is at the bottom, even more will drain when that bottom bolt is removed.

 

[Borchik]

You should just helicoil it and it will not have a problem again. That would be the proper way to do it. Drilling it out to a larger size will only make it harder to fix if it gets stripped out again.

 

[Jiggz]

If you can find a right size insert, I would go that route too. Make sure you used permanent thread sealant that is oil and fuel resistant.

 

[khoonie]

I found helicoil at the autoparts store. However, I must have somehow fouled up either the tapping (maybe went to far, no taper?) or the install, because the coil would not compress correctly. For the immediate time, I have temporarily installed a steel plug I found at Fastenal that fits the threads and I used the blue thread sealant and I made a gasket from a sheet of rubber/cellulose gasket material. The plug is not stainless steel - it is black steel. Can I get by with this for a few trips to the lake, or am I asking for trouble? I intend to try the helicoil again, but now I will have to tap it out to a larger size - a slippery slope... Thanks to everyone for your help.

 

[Jiggz]

What size engine are we talking about? To do this job properly, it is a must the LU must be taken off and properly drained. Degreased and make sure it is oil free to start with. Brake cleaner is very good on degreasing and getting rid of oil residue. If you did this, then the temporary fix you have right now should hold especially with the thread sealant.

 

[Scaaty]

Franks methods will work just fine. (Frank great idea on prop off, anode, etc). My 88 125 finally froze up too. Last year I just simple dropped the L/U, flipped it, drained, new impeller, and back on. My L/U is well sealed..(snapped a D/S quite a bit ago, redid all the guts with a new shaft). so couple years I'll drop it again, and drill and retap a new plug. Or try Franks method on pull the prop, etc. Frank, ya RULE on Force's!

 

[Frank Acampora]

Contrary to most opinions, DON'T use a helicoil. My experience with them is that they tend not to seal and also tend to either push through an open bottom hole or work their way out. Just retap to a larger pipe plug and be done with it. There is plenty of aluminum there. And next time listen to me! LOL

Black iron will rust relatively quickly. Be certain to coat the threads with sealer. After every day, reach down, dry the plug, and grease it. If you get desperate, a good welder can weld the hole closed and you can drill and tap it to whatever you want.

 

[khoonie]

Ha! I have to agree, Frank! Yes, I believe I will retap it for NPT and [hopefully] be done with it. I will probably have to tackle the LU next - the gears are not engaging like they should. But I hope to get through the rest of the summer before I do that - cross my fingers. I will update when I retap to the NPT size. Again thanks for all the help/ideas. Lots of good stuff there!

 

[foodfisher]

There's a remedy for that. Post another subject/topic/thread.

 

[Frank Acampora]

The gears in the lower unit are ALWAYS engaged--both forward and reverse. The drive dog clutch selects which set will propel the boat. THUS: The drive dogs are not properly engaging. So the question becomes: Is the engine popping out of gear when running? If so, the condition will only get worse as the drive dogs wear. OR, is it simply an adjustment issue? That can and should be fixed without waiting.

 

[khoonie]

Ahh! To answer your question: What happens is that when I try to put the engine in gear, especially in reverse, it clanks and chatters and does not seem to want to go in gear until I push the throttle lever much farther than should be necessary. I do try to engage it quickly to keep it from chattering, but I can tell it is getting worse. If I need to start a new thread for this problem, I will do so. It may be a few days before I can start working on the LU, though. However, I can see now that this is something which will need attention right away.

 

[Frank Acampora]

HEY! Its your thread. You can hijack it if you want! LOL

Sounds like an adjustment issue. First, you need to know if there is too much bias in forward gear. To do this, in the driveway with the engine off, put it in forward gear. now rock the prop back and forth between the dogs. If you feel a drag or hear the drive dogs and gear rubbing. there is too much forward bias.

Now, if it is making noise when put into both gears, that is a different story. You need to check for binding in the linkage and the cables. Cables that are too short or bent through too sharp of an angle will simply not function correctly. Ideally, there will be a 2 foot loop of control cable in the splashwell. Disconnect the shift cable at the engine and see if the control box handle moves easily. If it does, then the cables are not at fault. Check the timing tower and linkage for binding.

 

[khoonie]

Thanks again, Frank! As soon as I can get back to it I will check the adjustment. Depending on what that tells me, I will proceed accordingly - and will probably need more help. I did hijack my own thread!! :facepalm: I could start a new thread, cut and paste the info regarding the gear issue into it and go from there, if it would be a help for future searchers. What do you suggest?