Stuck and corroded drain plugs in lower unit

[Frank Acampora]

For you fellows with stuck drain plugs in your force 85 and up lower units: You don't need to remove the drain plug! Remove the prop, remove the anode and remove one or two screws holding the bearing spool. Remove the vent plug. Almost all the oil will drain out.
Actually, the factory recommended removing the spool once a year if the engine is used in salt water to prevent spool corrosion from splitting the case. So: it's only a little more work to remove the spool, clean and lubricate it and replace the o rings, than just draining the gearcase but it's well worth it

 

[eurolarva]

Re: Stuck and corroded drain plugs in lower unit

The question is how do you refill the lower unit if you cant use the drain plug?

 

[Frank Acampora]

Re: Stuck and corroded drain plugs in lower unit

Fill and vent plugs are on top of ventilation/cavitation plate.

 

[Frank Acampora]

Re: Stuck and corroded drain plugs in lower unit

I may have confused some people. This is for the Chrysler/ force 75 horsepower and up engines using the one piece lower unit.

 

[eurolarva]

Re: Stuck and corroded drain plugs in lower unit

If you have a totally sealed lower unit you must have two openings in order to fill a lower unit. If you attempt to fill a lower unit with the vent hole plugged no matter how much force you use to add the oil it will not go. If you have the bearing cage removed or even loose all the oil will leak out while trying to fill. Correct procedure with the over under vent drain plugs is to fill from the bottom till it is full then plug the vent hole then remove the oil dispenser or pump and replace the bottom plug. I dont see with your method how you can refill the lower unit.

 

[imported_fullforce]

Re: Stuck and corroded drain plugs in lower unit

8)

 

[Frank Acampora]

Re: Stuck and corroded drain plugs in lower unit

Again, this is for the Chrysler/Force one piece lower unit with a drain plug in the bottom and both a fill plug and a vent plug above the anti-ventilation aka cavitation plate.

with the engine vertical, the oil goes down the fill and the air comes out the vent. when oil comes out the vent, let the engine stand vertical for about 1/2 hour then top off the oil and reinstall the plugs.

 

[Matthew A.]

Re: Stuck and corroded drain plugs in lower unit

That's all good and everything but what does one do when corrosion makes it impossible or close to impossible to remove the spool and the drain plug is being uncooperative also?

 

[Frank Acampora]

Re: Stuck and corroded drain plugs in lower unit

I never said it would be easy! Plenty of WD40 and lots of work, aggravation, and time will get a corroded spool out. You may strip the threaded puller holes but just retap them larger. Also, use heat. It will destroy the O rings but at this stage of corrosion you will need to put in new ones anyway. Be careful! even if drained, there is still residual oil in the gearcase. And after removing the spool, you need to hone the internal surfaces that the O rings seal against to insure a good seal. External one only seals water from low pressure behind prop and is not critical, but internal O ring seals water out and oil in the gearcase.

Stuck drain plugs:

If it's an allen wrench type drain plug, they can be drilled out and re- tapped to the next larger size or a 1/8 pipe plug. You must use a new high quality drill bit and slow speed and high pressure, or you will melt the drill tip. If it is the flat head screw type, heat and an impact screwdriver, or lacking that, a very large flat blade screwdriver with a square shank; put a wrench on the shank and push in as hard as you can while turning. Also, You MUST curse a lot; it seems to help. And just remember, these engines always fight you-- nothing ever comes easy.

 

[Matthew A.]

Re: Stuck and corroded drain plugs in lower unit

Thank you for the quick reply Frank. One method I have been successful using when the lower units drain plug won't come loose is to lightly tap on the allen wrench with a hammer while applying torque to loosen the plug. Sometimes it comes loose after just a couple of minutes. Other times...as much as 20 minutes. It's a routine I go thru every four or five weeks due to a very small amount of water getting past one of the seals. We have put nearly 2500 hours on this motor in the four years we have owned it, plus however many hours on her by her previous owner/s, (it's a 1988 85 hp Force)the propeller shaft has a little bit of y and z play. I can't complain though, considering when I first got the motor and replaced the oil in the lower unit, what came out stunk badly of anarobic bacteria, was black and had the consistancy of yogurt.

 

[Frank Acampora]

Re: Stuck and corroded drain plugs in lower unit

Been there with my drain plug except I had the skill to round out the hex. So: I had to drill it. Luckily enough, an easy out removed the body of the plug.
Check the seals in the water pump lower plate. This plate is held on with the 4 water pump screws and 3 other screws. It covers the top of the gearcase and holds down the upper shaft bearing. It has one shaft seal, an O ring body seal, and two O ring surface seals located in two grooves around the plate. This has been a source of problems for me in the past. If the plate is bent, or if the gearcase is nicked here, (and it can be bent or nicked by prying it up to remove it) you can get leakage past those O rings. Unless the bend or nick is really bad, this leakage will not be a lot because this plate is only under water while the boat is sitting still or off plane.
Removing this plate is also another way to get out the old oil.
Use a bit of pipefitters teflon tape on the drain plug before replacing it . It helps for the next time.
Oh yes: The upper shaft bearing only comes as a unit with the drive shaft --very expensive! But it is also a standard bearing in several food processing machines and can be had at a bearing supply store for about 45 dollars.
A little trick for installing press fit bearings: Place on a 100 watt light bulb for about ten-fifteen minutes. It will get hot enough to slip right on but not so hot as to be damaged. Works every time.

 

[Matthew A.]

Re: Stuck and corroded drain plugs in lower unit

Light bulb huh?...That's a trick I'll have to remember. As for the water pump...already had to replace it. Except that no matter what I tried I couldn't get two of the wp housing bolts to come loose. ended snapping the heads of both of em below the surface. Thank God for JB weld. lol I would have replaced the gear case seals except two of it's housing bolts wouldn't come loose just as the wp housing bolts. Fearing the worst...I decided to forego it. I probably should have gone ahead and replaced them despite the hassle. I think the next time I have to deal with the wp I'll drill out any broken bolts and replace the bolts with studs as Force did on the newer units.

 

[chrismarion]

Re: Stuck and corroded drain plugs in lower unit

Since there is no point in starting another thread, unless this doesnt get answered, I have a problem with mine. I am waiting for my Rectifier to get here so I thought I would drain my L/U gear oil. Been 6 months, now my drain plug is stuck. The plug twisted my alan head socket and then stripped. After reading 13 pages of post's on this problem, I decided since its down anyway to go ahead and drill it out. Right now I am at 1/8 drill bit and I dont want to go any larger untill someone recommends
' What size plug to replace it with and where to get it' !!

Out of all those pages, no one said a size to replace it with. Just "drill it out and re-tap it". I know someone here has done it and knows what I need to get.

Thanks,
Chris

 

[Frank Acampora]

Re: Stuck and corroded drain plugs in lower unit

If it is an allen screw, the stock size is usually 5/16 fine thread I forget the threads per inch. If you have it drilled, try heating it and using an easy-out available at Sears. But just be careful easy-outs are tough but also hard and if you abuse them you can snap them. Then they are so hard you cannot drill them. The next size up would be either a 3/8 screw or a 1/8 inch pipe plug. The pipe plug takes a tapered tap and is more or less self sealing. But don't tap too far in or the plug will go right through. If you cannot get the old plug out at all, drill it with the next size drill below 5/16 to leave you a little slop room. If you are careful, a 5/16 hole wil leave enough meat for about 75% threads, which if I remember correctly will develop about 90% thread strength.
If the plug was a headless flat screw, it was either 3/8 inch fine thread or 1/8 inch pipe thread.

Ps : If you are real good, it is possible to drill out right to the threads and then pick them out with a tool like a dentists pick. This takes a lot of patience but the advantage is that you may not need to re tap the hole. Depends on the amount of corrosion and the amount of threads left.

 

[chrismarion]

Re: Stuck and corroded drain plugs in lower unit

Corrosion was not a problem. Yes it was alan head and it was stripped. I have almost all tools imaginable and my extractor set did nothing. That thing was in good so I drilled it out with a 1/8 drill bit, so your saying I can use ANY 1/8NPT plug?!?! If so I can get those at work, but I want to use the best I can. I will be sure not to tap all the way in, pretty meaty in there too if I might add! I would rather use a brass plug in hopes to fight against salt water.

 

[Matthew A.]

Re: Stuck and corroded drain plugs in lower unit

Just be sure that whatever plug used is made of a high quality stainless steel. That way any corrosion that occurs only affects one and not both metals. Plus, as you have already experienced...if the plug is made from too soft a metal it is more likely to be damaged should it seize up. As Frank mentioned, to help prevent future seizures use thread tape and or a good waterproof grease on the threads prior to reinstalling the plug.