Lower Unit Rebuild Questions

kameika · Oct 19, 2003

Hi all. I just pulled the lower unit for service, as there was water in the oil. Whilst the LU is off the engine; I figured it would be a good time to rebuild the water pump. ..And maybe prevent another LU removal in the next few years. Questions: 1. What would you regard the life expectancy for a water pump? 2. There was a very slight amount of burned plastic material just outside of the water pump housing. The water pump housing appears intact and in good shape. Would it be a mistake to re-use the housing, assume I put a "rebuilt kit" in? 3. My service manual recommends a few "OMC$$$$" sealants and lubricants: Are there suitable alternates for "Adhesive "M", "OMC Gasket Sealing Compount" and "OMC Moly Lube?" I admittedly do not like going to the "OMC dealer." I regard them as extortionists. Any good substitutes for this? 4. Finally, are there any good recommendation or tricks for re-sealing the lower unit, outside of what's listed in the service manual? Many Thanks! Ken Ameika Red Bank, NJ

JB · Oct 19, 2003

Re: Lower Unit Rebuild Questions

Hi, Ken. I suppose it would be helpful to know what engine you have. Let us know.

Consider the useful life of an impeller as 1 calendar year.

Joe Reeves · Oct 19, 2003

Re: Lower Unit Rebuild Questions

Ken.... You may find the following information on sealer and gaskets useful. Also, you can destroy a impeller quite quickly by runing through a sand bar etc. The life of the water pump varies, but with normal use, I would say not to let it go beyond two years without a thorough inspection. I recommend that you install a complete water pump kit assy (includes the housing), not just the impeller. (Gasket Sealers) (Usually available at any reliable automotive parts type store)(J. Reeves) Do Not use any type of sealer on outboard carburetor or intake manifold gaskets as this would cause blockage of various fuel/air passageways. Also, there are new type gaskets, including head gaskets, which are used through out the engines that are coated with a substance that gives a shinny appearance to them. These gaskets are coated with a self sealer and are to be installed as is.... no sealers! Older style head and fuel related gaskets that are not coated with this substance are to be simply coated with oil.... nothing else. All other gaskets (hopefully I've not overlooked anything above) should be coated with Gasket Sealer (the type that comes in a can that has a small brush in its screw off cap). This also pertains to some water pump installations that use a gasket between the plate and the lower unit housing. Marprox Sealer 1000 or OMC Adhesive or Boat Armor Sealer 1000 (same substance) should be used on any metal to metal or metal to plastic surface (such as impeller hsg to plate) to eliminate air leaks. It should also be used on the Spaghetti tubing that is used on many powerhead crankcase halves, lower unit skegs, etc. I have found that this substance works quite well on various "O" Rings such as what are found on lower unit carrier and upper driveshaft bearing housings (Note that this substance is obviously not to be used on all "O" Rings). DO NOT use any sealer on the large "O" Rings that are used on the upper and lower crankcase heads (The housing/heads that slide over the top and bottom of the crankshaft). On those "O" Rings, use only a coating of grease. The exception of surface to surface contacts pertains to the later model matching crankcase (block) halves (which does not incorporate spaghetti tubing) which call for "Gel-Seal", or any other surface that calls for Gel-Seal. This substance seals in the absense of air, and if called for, must be used. One other form of Gel Seal that can be substituted is "Loctite #518". Nothing else that I know of will do! I advise against using silicone or permatex on a outboard engine. It simply will not function properly. The exception to this (as per OMC's recommendation), is to use the black Permatex (heavily) on the gasket 306242 which seperates the inner exhaust tube from the exhaust housing on the 1959 35hp and 1960 to 1970 40hp OMC outboards

kameika · Oct 19, 2003

Re: Lower Unit Rebuild Questions

Thank you, Gentlemen.. I do have a 1987 OMC Seadrive 2.7L, 235HP. I did do an inspection to that water pump, and have encountered a rough situation: That pump impeller is jammed onto the transfer shaft. I've tried to pry it off with a putty knife to no avail. Should I try to cut it off with a Dremel tool? It's sitting in my woodshop with some WD-40 soaking on it.. I am not optimistic the lube will get it off. It is interesting, though: The engine has been carefully maintained--and the impeller of four years appears in good condition; except for the gob of melted plastic by the outlet port. You're right, though: An annual or bi-annual inspection is wise practice. Any further assistance would be greatly appreciated. Ken

Hooty · Oct 19, 2003

Re: Lower Unit Rebuild Questions

You may have to use your Dremel tool to remove the impeller and you're correct, the WD-40's not going to do a thing. It's not a penerating compound. The WD stands for "water displace". Get some PB Blaster, Kroil or some other legitimate penetrating oil. c/6 Hooty

rodbolt · Oct 19, 2003

Re: Lower Unit Rebuild Questions

Hello I keep reading post about melted housings and plastic blobs. shows someone is running or starting the engines with no water, as the only way to melt a housing is to run it dry. if the housing shows any signs of melting it should be replaced. I recommend replacing them anyway. in fact in my shop its the only way, I tell my customers if you want half a job the guy down the road is your man. yes Ken I dont give much of any oil a chance. I use a 1" wide sharp chisel and cut them off. takes about 2 min. Good luck and keep posting

kameika · Oct 20, 2003

Re: Lower Unit Rebuild Questions

Thank you again, Gentlemen. The Impeller is off, thanks to some cutting with the Dremel tool, and a final seperation with a 3/4'' chisel. It took just a little longer than 2 minutes, though.

The drive shaft is pitted in the area around the water pump. Is it a good idea for me to sand it down--or leave it? My concern, of course, is the condition of the shaft at the seal to the lower unit. The main reason for my adventure is to re-seal the LU. Any advice for this aspect of the project? Any experience out there with pitting/corrosion to the shaft at/near the lower unit seal? Ugh. I just learned my local OMC dealer sold me the wrong seals--AGAIN. Since the son, an account, took over from his father (a mechanic,) the place has fallen. The son can't seem to get anything right. When you're charging top-dollar, you need to do more than simply push (wrong) product out the door. Further, the store is messy since sonney-boy took over. I'm disappointed. Best Regards- Ken Ameika Red Bank, NJ.

wilde1j · Oct 21, 2003

Re: Lower Unit Rebuild Questions

Try Bry's in Neptune for parts. They have a neat and clean operation and are knowledgeable.

ledgefinder · Oct 21, 2003

Re: Lower Unit Rebuild Questions

If the driveshaft is corroded, grooved, or otherwise not in good shape right where the seal rides, it needs to be replaced. It's not uncommon in salt water units with few years on them, if they've been used a lot. If the shaft is just corroded above the seal(s), it's OK to reuse, but wrap some plastic sheet or something around the shaft to protect the seal lips when you slide it on.

ledgefinder · Oct 21, 2003

Re: Lower Unit Rebuild Questions

If the driveshaft is corroded, grooved, or otherwise not in good shape right where the seal rides, it needs to be replaced. It's not uncommon in salt water units with few years on them, if they've been used a lot. If the shaft is just corroded above the seal(s), it's OK to reuse, but wrap some plastic sheet or something around the shaft to protect the seal lips when you slide it on.

kameika · Oct 21, 2003

Re: Lower Unit Rebuild Questions

Thank you, sir. Just inspected that seal, once again. There is pitting around where the pump impeller was once stuck. However, the orange material I thought was "rust" was something else. Perhaps an adhesive or a stain from the brass core of the impeller. As I am going to replace that seal, I *Carefully* pried it away with an X-acto knife to inspect: It looks clean under that seal. Whew. Ducked that bullet. (I hope.) To replace that seal is a frightening prospect: I need to remove a plate + bearing housing; I believe. This is outlined in the service manual. What scares me is the fact they (the OMC service manual) shows "Special OMC tool" to remove the shaft. All I am interested in doing is replacing this seal and the gasket; if necessary. Is this special removing tool (a screw-jack tool, or sorts) will be required? Is there a work-around? Thank you all again! I'm sorry to be such a pest. Can you tell from these posts that I am an electronics guy? (not mechanical) ..And I will check that place in Neptune. I'm finished with the other place. Ken

OBJ · Oct 21, 2003

Re: Lower Unit Rebuild Questions

Hi Ken... If you look under the impeller plate you will see four bolts holding down the driveshaft bearing housing. Remove the four bolts and gently remove the bearing housing. Try not to mar the surfaces. If you do, just sand them down a little since the O'ring really does the sealing. Just be carefull when installing the housing with the new seals. The splines at the top of the driveshaft can cut the rubber on the new seals. What I used to do was take a piece of thin plastic like 4 mil and put a piece over the splines. This will help protect the seal rubber. Just outta curiosity, could you post your model number? Don't remember a 235 in 87'. Probably my mind going south but would like to be sure. Thanks and keep posting.....Jim

kameika · Oct 23, 2003

Re: Lower Unit Rebuild Questions

Hi.. The full name is 27ASPHD, 2.7 Liter S-Type. I do appreciate the information on the re-seating of the seal. I'm going to hold work until this upcoming weekend. Thank you all, Gentlemen. -Ken.

kameika · Oct 25, 2003

Re: Lower Unit Rebuild Questions

Conclusions! In the event anyone out there has a similar problem.. The "Bearing Carrier" was pulled carefully from the LU housing (more on this later..) -- And the seal was discovered to have a very small crack. The seal, if you use your imaginiation, is shaped like a hollowed-out mushroom. The weak part of this part is the section between the "stem" and the "head." In short, a tiny crack formed there. ..This probably only allowed a drip or two of water per hour. Enough to make the oil milky. Here's a suggestion to pull the bearing carrier, because it is a bear to remove: I used a steel plate, a wonderbar ( a crowbar, ) and a long carriage bolt with a nut on the end. The goal was to form a "pullrod." The head of the carriage bolt rode under the lip of the bearing carrier. The nut, threaded to an appropriate length, was loosely coupled to the working-end of the crowbar. The crowbar was "rocked" on the piece of steel, riding atop the lower unit. (shift seal housing + shift rod removed--easy to do.) This pull-rod configuration worked like a charm. I was cautioned about the following: The "home outboard mechanic" routinely uses a screwdriver to pry the bearing carrier out. * Be Warned * The thin walls of the LU are easily chipped/cracked with this method. (I see why.) If you crack the LU housing; you're SUNK. Anyhow; For a mere $52, Boat-US sold me a LU seal kit. For an additional $62, a full pump kit. Hence, for $125.00, the LU is (in-progress) re-sealed, re-pumped, and oil changed. I'll report back my total time cost, as a first timer; when this job is done. I'd reckon, it will be < 6 hours, though. The next time will be probably less than 2 hours. I hope some future guy will read this thread and take on the challenge. All the best--and thank you for the help, Gentlemen. Ken Ameika 23' Larson, "Better Days" Red Bank, NJ

OBJ · Oct 25, 2003

Re: Lower Unit Rebuild Questions

Thanks for the come back Ken....nice to see a situation work out for a guy. Keep up the good work.

Lower Unit Rebuild Questions

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