I knew things were going to good /1992 2 stroke 40hp Yamaha

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Douglasdzaster

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Location
Smithville,Texas
LOCATION
Smithville, Texas
Hello again everyone,here’s what I got.

In August I changed the gear oil in the lower unit. I noticed a little water in it and freaked out of course. I remember I didn’t install new washers (like Yamaha says to)the last time I did it. So I used the boat a few trips then opened the drain to se if I had water and drained out quite a bit of gear lube and no water. So I chalked it up to the washers.

I finally got around to cleaning up the power head with all the dead bugs after Sundays night fishing I had posted about.
I degreased and washed the power head down then after a few minutes in the sun and drying it off I wanted to run it to flush it and warm it up so it would finish drying.
I have a plastic drum that I cut down some and by lowering the trailer jack I squeeze it under the outboard then raise the jack back up and it’s in plenty of water. I also leave a hose running in the barrel so it’s always getting fresh water. Only run it this way 10 minutes at the most.

After it was done I removed the drum and let the motor cool down then treated the power head with a corrosion inhibitor and detailed it.
While wiping down the lower unit I noticed what’s in the picture I am posting.
First I said the seals are out behind the prop. This was coming from between the prop and the case. But then I realized it looked more like mud instead of gear oil with water in it.
I wandered if beaching the boat that night had something to do with it. When I tried backing off maybe I sucked in some mud or something?

It was dark by now so tomorrow I’ll pull the prop and take a look then drain some gear lube to check for water.


Meanwhile I wanted to see if anyone recognize what’s running down the scag. I wiped it off first but it was still oozing out so I took this picture.
FFBFF8C1-F461-4895-9B7D-45D5D318A52F.jpeg the camera makes it look more like oil but it is very thick looks like mud or sludge and I use blue gear oil.
 
You have no luck at all do you? Hopefully it is nothing major.
Thanks Sonny1.
Sure I do. I have all the luck I can stand. I have bad luck.
You know I don’t mind doing the work. Heck the seals are $12 for both (that’s the prop shaft). I just can’t afford to go buy specialty pullers etc.
Especially since I probably won’t ever need them at least for a long time.
I going to probably have to get a pressure pump to test it for sure.
Wish there was a place like the auto parts stores that rented the tools.
I’m going to have to figure a way of getting just the seals out without scratching the prop shaft.
I’m about to go out there now and pull the prop and drain the unit.
Then my denial will be over.
Again I say. This will not keep me from the water!!
 
If it’s the gear case that means water is in it. I won’t be able to get to it for a few days. Is it ok to leave it drained and empty or should I try keeping gear lube in it until I get my stuff together ?
 
Does the motor run good? Kinda looks like unburnt fuel/oil mix that can get produced when one cylinder isnt firing or something like that. It will be medium brown like that in those cases. I've had it happen twice and both times looked like that and were due to spark failing under load due to bad ignition components. You get the same crud when you idle it a lot, especially on muffs or in a barrel, but thats typically very black like used motor oil. I've never had a lower have seals so bad it leaks out gear oil when not in use.

Onto the lower....I made my Mity-Vac brake bleeder pump into a lower unit pressure tester. Simply replace the hose on it with one from a lower unit fill kit. Drain the lower and screw it into one of the fill or vent ports and seal off the other. Then pressurize it to 10 psi or so and see if it holds pressure. Most manuals say it only has to hold for 15 seconds or so but I'll leave it for 15 min if not more. If you lose pressure squirt with soapy water and find the leak. I also pull a vacuum on it since the brake tool does both. If you don't have one you may could rent one from the auto parts store. If you do have to replace any seals, the shift rod seal is usually pretty easy at least. The driveshaft seal is too if it isnt corroded too bad. I was able to get the driveshaft bearing carrier out of my 1988 Yamaha 30 without any special tools even though it was really stuck in place. I take my prop shaft seals out without special tools too although my method is kinda risky - I use a sharp pick to punch through the outer one in a bout 4 places, put in some sheet metal screws into the holes and then pull it out with pliers, vise grips, or pry with screwdriver. Not too bad after you have done a couple. Just have to make sure you dont scratch the inner or outer seal surfaces. I'm sure you could rig up a way to use a regular flywheel puller on the prop shaft to evenly pull the seals out. I repeat for the inner seal. I use a matching sized piece of thick wall pvc pipe to install the new ones since the prop shaft is in the way.
 
Does the motor run good? Kinda looks like unburnt fuel/oil mix that can get produced when one cylinder isnt firing or something like that. It will be medium brown like that in those cases. I've had it happen twice and both times looked like that and were due to spark failing under load due to bad ignition components. You get the same crud when you idle it a lot, especially on muffs or in a barrel, but thats typically very black like used motor oil. I've never had a lower have seals so bad it leaks out gear oil when not in use.

Onto the lower....I made my Mity-Vac brake bleeder pump into a lower unit pressure tester. Simply replace the hose on it with one from a lower unit fill kit. Drain the lower and screw it into one of the fill or vent ports and seal off the other. Then pressurize it to 10 psi or so and see if it holds pressure. Most manuals say it only has to hold for 15 seconds or so but I'll leave it for 15 min if not more. If you lose pressure squirt with soapy water and find the leak. I also pull a vacuum on it since the brake tool does both. If you don't have one you may could rent one from the auto parts store. If you do have to replace any seals, the shift rod seal is usually pretty easy at least. The driveshaft seal is too if it isnt corroded too bad. I was able to get the driveshaft bearing carrier out of my 1988 Yamaha 30 without any special tools even though it was really stuck in place. I take my prop shaft seals out without special tools too although my method is kinda risky - I use a sharp pick to punch through the outer one in a bout 4 places, put in some sheet metal screws into the holes and then pull it out with pliers, vise grips, or pry with screwdriver. Not too bad after you have done a couple. Just have to make sure you dont scratch the inner or outer seal surfaces. I'm sure you could rig up a way to use a regular flywheel puller on the prop shaft to evenly pull the seals out. I repeat for the inner seal. I use a matching sized piece of thick wall pvc pipe to install the new ones since the prop shaft is in the way.
Thanks for the reply and sharing your knowledge I sure appreciate it.
I actually think I have a couple things going on. I do believe the sludge picture is un burnt fuel/oil. I’m going to make a reply with more pictures of what I have.

I’m sorry I came back to you and editing my reply.
I didn’t answer your question. Yes the motor runs good. Actually since I just rebuilt the boat and took a lot of weight out the way I did the flooring. I had to watch my rpms because at wot it wants to hit 6k instead of 5-5500 rpms. I’m going to have to report it because I know it’s capable of better performance. The little lady will be glad to find out about that. Lol
 
Last edited:
Ok. Here’s what I got. I believe the first picture I posted is un burnt 2 stroke mix. Also my portable fuel tank is the old style with a manual vent 6 gallon.
I never used more than 2 or 3 and that’s doing a lot of running up and down the lake. When the boat is in the driveway I store the tank in my shop and since it’s manual vent I have to leave it open. So the gasoline evaporates some. Before each use I add fresh mix top it off. I use a 2 cycle semi synthetic oil which works great. With fresh fuel the only time it smokes is when I first start it. And if I do some idling I always run it wot before bringing it home. I have a new tank that I want to try out so I’ve been trying to run this one as low as I can. The last three outings I haven’t put any fresh mix and the gas has been evaporating making the mix to rich. The last two trips it’s smoked a lot and I figured this was the problem.
The last trip which was at night all we did was idle for a long time and I didn’t run the carburetors dry that time either. Yesterday in the barrel it smoked like a train and I’m not going to rev it unless I’m on the water.
After about 10 minutes I disconnected the fuel line and ran them dry. Then it sat in the water a couple of hours before I drained the barrel and removed it. I’m working on another project at the same time.

Today I pulled the prop and all my blue grease had turned green there’s a comparison picture of some fresh grease on a paper towel.
I checked the gear case and was full but I drained it anyway. At first it looked new then I noticed what looked like water coming out with it. At the same time though I had a little clean water that was in the unit coming out of the pickups. I know there was a little water in the gears because I saw it hit the pan with the oil stream. And it’s also pretty thin IMO. I dipped a paper towel in it and it made the paper towel transparent.
I have pictures for y’all to check out and please give me your input where to proceed. I cleaned the prop shaft seal as best I could.

It looks to me like there’s a fraction of space between the seal and prop shaft. It had grease in it there and I think it’s supposed to be a better seal than that but I could be wrong it’s happened twice before (2 ex wives).
Let me know what y’all think please. At least it’s not what I was afraid I was going to see when I drained it.
I’m tempted to refill it get some fresh fuel and run it like I stole it to get its throat cleared.

4CB17EA4-C9F3-4399-9CA7-E2C5736BE12D.jpeg first pic again.A5BFC223-B006-4281-A028-47FE879CEFD5.jpeg grease comparison of the same grease new is on paper towel. I think the un burnt mix did this.27843A11-E333-4391-BA0E-F34989D5987E.jpeg885CC8F8-4801-4B46-8914-458158CBEFF6.jpeg
02692C1C-D632-4909-9666-F6EC9BE43842.jpeg
8ACBA78E-7795-454B-A90D-FF7A38D1FA10.jpeg You can’t see it but there’s about a cup or so of water and sludge in the bottom of the housing. I pulled the trim pin earlier and let the motor rust all the way against the boat and more drained out. I gotta figure out how I’m going to get the rest out.
 
Probably exhaust crud from unburned 2 stroke oil. I see it often in two stroke motors with thru hub exhaust. Check your lower lube and if you find no water, then two stroke oil in the exhaust water is your culprit.
 
If there is a gap between the prop shaft and the seal then you have bearing trouble. Up and down movement in the prop shaft should be almost imperceptible, a little bit of endplay is normal.
I agree. I'd grab the prop shaft and trying moving it back an forth in all directions and see if you feel any play. If you can feel it then that isn't a good sign for your bearings. If it feels ok, then you could use a dial indicator and check for runout as you rotate the prop shaft.
 
Honestly though the latest pics of the gear oil look fine to me. I'd for sure pressure test it while its drained though and you need to remove the lower when you do it so you can access all of the seals when its done.
 
If there is a gap between the prop shaft and the seal then you have bearing trouble. Up and down movement in the prop shaft should be almost imperceptible, a little bit of endplay is normal.
Thanks for the reply. I checked and there’s not any play in the shaft so I ruled out a bearing but the lower unit is new territory for me. Up till now I changed the gear oil regularly and kept the prop shaft greased. I used my caliper today and took measurements from the housing to the shaft all around it and no difference. There’s probably a better way to check for a bent shaft but this is what I came up with.
 
I agree. I'd grab the prop shaft and trying moving it back an forth in all directions and see if you feel any play. If you can feel it then that isn't a good sign for your bearings. If it feels ok, then you could use a dial indicator and check for runout as you rotate the prop shaft.
I appreciate the advice. I couldn’t find any play at all in the shaft.
But I’m afraid you lost me. Can you elaborate more on a dial indicator and checking for run out?
When I spin the prop by hand it has a slight rubbing noise and rotates about 2-3 times before it stops.
Back when I ran bigger outboards I could spin the prop on them by hand and they spun more freely.
 
Sounds like a slight bend in your propshaft, but it might not be enough to worry about, unless you keep getting water in your fuel.

I know people who have had pretty bad bends for years, and they just drain out the water every once in awhile and keep on going. Or, find a blown motor on Craigslist and use the lower from it. You will be fine, one way or another.
 
Sounds like a slight bend in your propshaft, but it might not be enough to worry about, unless you keep getting water in your fuel.

I know people who have had pretty bad bends for years, and they just drain out the water every once in awhile and keep on going. Or, find a blown motor on Craigslist and use the lower from it. You will be fine, one way or another.
I went ahead and refilled the lower unit yesterday because I didn’t want it ti sit dry.
We’re having a church picnic at a small power plant lake where I take it for test runs and a little bass fishing.
I’m supposed to have it there and give boat rides. Especially to little ones that have never been in a boat. I’m thinking about going ahead and take it.
That way I can get in some wot time with fresh fuel mix to get the sludge out.
Then I’ll check for water in the lower and see what I have.
That oil I drained has been in there for three months with a lot of time of the water. All day trips.
 
I appreciate the advice. I couldn’t find any play at all in the shaft.
But I’m afraid you lost me. Can you elaborate more on a dial indicator and checking for run out?
When I spin the prop by hand it has a slight rubbing noise and rotates about 2-3 times before it stops.
Back when I ran bigger outboards I could spin the prop on them by hand and they spun more freely.
Basically a dial indicator on a mount is secured somewhere where the indcator is in contact with the prop shaft. Zero the gauge and rotate the prop shaft while the lower unit itself is fixed/stationary and record the max and min changes on the gauge (aka runout). There is a spec for the allowable in the service manual which is prob pretty standard across manufacturers and HP ranges. Best way to lock it all down for a basic shade treee mechanic is probably to remove lower and put skeg in a vise and attach the magnetic indicator arm to the vise itself. All that said, personally i'd pressure test first and if good not worry about checking the prop shaft.

Again I cant recommend the mityvac tool enough. Great for outboard lowers and you can use it as intended to bleed brakes on your vehicles by yourself
 
Basically a dial indicator on a mount is secured somewhere where the indcator is in contact with the prop shaft. Zero the gauge and rotate the prop shaft while the lower unit itself is fixed/stationary and record the max and min changes on the gauge (aka runout). There is a spec for the allowable in the service manual which is prob pretty standard across manufacturers and HP ranges. Best way to lock it all down for a basic shade treee mechanic is probably to remove lower and put skeg in a vise and attach the magnetic indicator arm to the vise itself. All that said, personally i'd pressure test first and if good not worry about checking the prop shaft.

Again I cant recommend the mityvac tool enough. Great for outboard lowers and you can use it as intended to bleed brakes on your vehicles by yourself
Thank you thank you!
I was trying to figure out how to check the shaft. Didn’t know what tool it would take. I’ve been looking at the mityvac’s. Just got to pull the trigger at the right time.
 

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