To Rebuild Or Replace...A Lower Unit

[TheKid]

I have a leak somewhere in the lower unit of my Tohatsu 140. I changed the oil the other day and found a small amount of contaminated oil.

Question I have is, how hard is it to rebuild these? Any special tools required?

Considering there were no metal shavings and the small amount this leads me to believe I caught it early. I assume I'll just have to replace some seals and maybe swap some bearings just because I'm in there.

I am comfortable doing lots of repairs. I have rebuilt a few motors in my life but never ripped apart a transmission.

Thoughts from someone who has actually done it would be great.

By the way, my dad is a TV repair man, so I have an awesome set of tools!!!

[fitz73222]

Hey Kid,

Lets first understand what you mean by contamination. Water, black mud,creamy white gearoil? What did you see and how much? When is the last time the gear oil was changed. There are different ways to approach this.

[jcaesar625]

I had my lower unit rebuilt. After labor and parts, and I was probably in it for ~$700. Then yesterday after 4 trips on the rebuild the drive shaft broke. I could have bought a new lower unit for $845.

http://texasoutboards.com/Products/tabi ... fault.aspx

[pete]

may just be a seal,behind the prop,refill wilh fresh gear oil,take it out and run itchech gear oil,if it looks milky you have a water leak,there is a seal behind prop that sometimes gets fishing line in it and it ruins the seal.take off prop and check it.good luck and report back.rebuilding lower units is best left to the pros,special tools are needed to set the gears to correct specs.however the prop seal can be user replaced.check a manual.

[TheKid]

Mayonnaise!

Found maybe 10% mayo first. Swapped lube, fished for a day and found 20% mayo again.

Yes, I need to replace a seal. However, I'm not sure the detail involved in replacing it. Assuming I need to take apart the lower unit, wouldn't it be a good idea to replace some other parts?

Like a timing belt in a V-8. You don't just do the belt, you swap the pump and pulley as well because you are already in there.

Again, I haven't messed with a lower unit before, aside from water pumps and lube changes.

Maybe I'm making a mountain out of a mole hill, I dont know.

[fitz73222]

There are four points of entry for water; propshaft seal, driveshaft seals, shiftshaft seal and lube washers. Lube washers behind the fill and vent screws are the easiest to fix and can lead to alot of water if they are bad or missing. Dig the old ones out with a pick and replace them for $1.00 if they are visibly bad. Take off the gearcase, remove the water pump housing and propeller/thrust washer and look for visibly damaged seals. Take the gearcase to a shop and have it pressure tested and you will find the leak. 12-14 psi max for the check and should hold pressure for 10-15 minutes or it will bubble through the bad seal with a little soap sprayed on it like finding a leak in a tire. Also look for fishing line on the propshaft after you remove the prop. Fishing line will cut that seal. Most outboards are pretty easy to replace the faulty seals without special tools. Get a decent manual for the engine and walk through the steps. If you can build an engine, you can do this job without issue.

[flounderpounder225]

There are four points of entry for water; propshaft seal, driveshaft seals, shiftshaft seal and lube washers. Lube washers behind the fill and vent screws are the easiest to fix and can lead to alot of water if they are bad or missing. Dig the old ones out with a pick and replace them for $1.00 if they are visibly bad. Take off the gearcase, remove the water pump housing and propeller/thrust washer and look for visibly damaged seals. Take the gearcase to a shop and have it pressure tested and you will find the leak. 12-14 psi max for the check and should hold pressure for 10-15 minutes or it will bubble through the bad seal with a little soap sprayed on it like finding a leak in a tire. Also look for fishing line on the propshaft after you remove the prop. Fishing line will cut that seal. Most outboards are pretty easy to replace the faulty seals without special tools. Get a decent manual for the engine and walk through the steps. If you can build an engine, you can do this job without issue.

Fitz is correct, all fairly simple, corrosion is your worst enemy.  Here is just one item I made up to pull the bearing carrier, which is the part you will remove from the prop shaft to replace the seal in the carrier.  Get a regular steering wheel puller from autozone, go to the hardware store and buy some long bolts, of the same metric size that your carrier is held in with.  Once the prop is off, you can take a flashlight and look down into the exhaust hub, you will see the bolt heads (probably 4 of them)  The long bolts are so the puller can sit behind the prop shaft and the bolts can reach down ion the hub and thread into the carrier, there should be some threaded holes to accept the bolts.  Then it is just like pulling any other carrier assembly.  You may get lucky and the carrier will pull out with a jerk by hand?  Clean the gear case out with some mineral spirits or something like it, check for metal shavings, I wouldn't go into the gears unless there was a lot of shavings.  Install the new seals, put some oil on the shaft, and bolt the carrier back in.  I have taken the gears and everything out using long needle nose pliers, it is not that hard, however, as I think Pete said, setting up new gears requires shimming just like a rear differential, and I would leave that up to the pros.  Good luck
Marc

[wingtime]

By the way, my dad is a TV repair man, so I have an awesome set of tools!!!

Totally classic dude!

[John Jones]

Very good advice above.  
If you have not found any metal shavings, the worst you have is the carrier seals are leaking and at best just the prop shaft seal or the plug gaskets.

[TheKid]

Thanks guys.

Yes I do need a manual, usually that is the first thing I do when I get a new motor. However, I'm having a hard time locating a true technician service manual for this motor. All I can find are the generic 9hp -140hp manual for motors from 1990-2011. Maybe that's all they make I don't know. My previous experience has worked so far. But I'm not going to attempt this with out a manual. I guess the generic one will have to do. That and an exploded assembly drawing.

We shall see! I'll let you know what I find.

[Capt. Bob]

Thanks guys.

Yes I do need a manual, usually that is the first thing I do when I get a new motor. However, I'm having a hard time locating a true technician service manual for this motor. All I can find are the generic 9hp -140hp manual for motors from 1990-2011. Maybe that's all they make I don't know. My previous experience has worked so far. But I'm not going to attempt this with out a manual. I guess the generic one will have to do. That and an exploded assembly drawing.

Kid,
Just by chance you haven't gone to the Tohatsu site,
They list three manual sources for their outboards. One is Clymer, another is Helms and last is a factory book through a Tohatsu dealer.

All my years (and my Father's as well) we used the factory manuals supplied by Helms for both Ford and Gm autos. They were very good. I just purchased a factory service manual for my 91 200 Yamaha and I'm just a little disappointed. I first had a "generic" Seloc and opted to spend a fair amount on the original. Comparing the two, the factory doesn't have photos (unlike OMC manuals) and that can be a help on some of the repairs.
Here's the link but you probably have been here before.

http://www.tohatsu.com/tech_info/faqs.html#Q2

#2 and good luck.

[TheKid]

Thanks Bob, yes I have seen those.

I haven't bought one because I was looking for a more detailed manual. But I guess that's it so I will be buying one or try to find a download somewhere.