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Nissan NS3.5A lower unit oil seals

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Pfmet

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Good day all, I’ve got foamy oily goo running from the weep holes between the gear case and shaft housing so I’m assuming The seal on the drive shaft is shot. I would also assume the time would be right to change the seal on the prop shaft as well. However it appears f rom the schematics that the upper seal would be exposed to water, hence the notable leak, but the prop shaft seal is behind the water pump case though there doesn’t appear to be a water seal of any kind on the prop shaft between the impeller and the oil seal so I guess there must be water in there as well. Are these seals able to be changed without special tools if care is used and are ther likely to be bearing issues I should prepare myself for. Have I seen that Nissan/Tohatsu parts are availabl e here somewhere? Hope all your projects go well and thank you all for being here. Best, Peter
 
On the 3.5A2, the water pump is aft of the prop housing. The complete LU seal kit is
309873210MGASKET SET, LOWER UNIT$12.80

It has one seal, one o-ring, and 2 drain plug gaskets.

There is indeed a separate shaft seal for the drive shaft (tall and odd looking). It does not come in the kit.
309602230MOIL SEAL$9.78


The prop shaft (normal type)
309601110MOIL SEAL$6.67
Which fits into the wp housing (inside), comes in the kit.

Yes, we change them with no more than a socket as a ram in a vise.
Confirm that you don't just have unburned TCW-3 oil in the gooey area.
 
Thank you Paul. Where to order parts as I need head and shaft housing gaskets if I want to check and clean the water jacket. This motor is a 1996 lightly used but never been apart. The drive shaft seal does double duty as the guard tube grommet it appears that’s one piece. And I assume I must remove the e-clip and bevel gear to retract the lower drive shaft in order to replace the upper seal? And the lower seal is pressed into the water pump case? Can I order new bolts for the head and housing or do we shop appropriately sized stainless off the shelf. What’s the best grade stainless for that job? Would it be the hardest? I appreciate your time and patience. The help of you experts who are willing to share is a gift of the internet. Best, Peter
 
And a further question for the masses. Any tips on r3moving what feels like seized head bolts? If I get the wiring out of the way can I apply heat to the head bolt with a torch....gently and rap away as it cools? Applying 50/50 acetone and ATF as a penetrant. I’ve had very good luck with larger (3/8) bolts this way but this is more delicate and crucial. Thanx again, Peter
 
You may find that this is a " generic " motor.------Your local Mercury dealer may be able to get you the parts.----Also sold under other brand names too.
 
Pfmet said:
Thank you Paul. Where to order parts as I need head and shaft housing gaskets if I want to check and clean the water jacket. This motor is a 1996 lightly used but never been apart. The drive shaft seal does double duty as the guard tube grommet it appears that’s one piece. And I assume I must remove the e-clip and bevel gear to retract the lower drive shaft in order to replace the upper seal? And the lower seal is pressed into the water pump case? Can I order new bolts for the head and housing or do we shop appropriately sized stainless off the shelf. What’s the best grade stainless for that job? Would it be the hardest? I appreciate your time and patience. The help of you experts who are willing to share is a gift of the internet. Best, Peter
Click to expand...
I can help you with parts; for that matter, any Tohatsu dealer should be able to help you. The head bolts are stock SS bolts. Here is the parts catalog diagram that shows how it goes together:
002-21040-4_FIG06A.JPG
 
Pfmet said:
And a further question for the masses. Any tips on r3moving what feels like seized head bolts? If I get the wiring out of the way can I apply heat to the head bolt with a torch....gently and rap away as it cools? Applying 50/50 acetone and ATF as a penetrant. I’ve had very good luck with larger (3/8) bolts this way but this is more delicate and crucial. Thanx again, Peter
Click to expand...
I would probably just leave the bolts alone. If you feel you are overheating, run salt-away (or just a lot of vinegar) through to dissolve the corrosion. Since the bolts go into aluminum, your mileage may vary when trying to free them with penetrating oils. If the head gasket is not leaking, just as good to just dissolve the corrosion. Otherwise, odds are you will end up drilling out a couple of the bolts and re-tapping. Just the nature of aluminum.
002-21040-4_FIG07A.JPG
 
racerone said:
You may find that this is a " generic " motor.------Your local Mercury dealer may be able to get you the parts.----Also sold under other brand names too.
Click to expand...
The alternate brands buy from Tohatsu and mark them up. Better pricing right from a Tohatsu dealer.
 
The party might have a Mercury dealer within walking distance, I do not know.--------Did Tohatsu make these motors or just market / sell them ?
 
Just to get up to date, the head cap is off and the portside of the water groove around the cap was plugged solid. The cylinder water jacket was cruddy but basically clear. This motor has never been run for very long and I don’t believe any overheating damage was done. I’d thought of vinegar but I doubt it would have resolved this issue. I broke one head bolt. Welded a nut on the 1 1/2 threads protruding and worked it out with heat and Super Cold. The head bolts have a 7 forged into the top of the hex head. There are varying discussions on the meaning. Some say it’s an older Japanese grading system representing grade 8.8 which would make sense for a head bolt. Others were not so sure. Does this sound right for those head bolts. They’re definitely not stainless which I assume would at least stretch somewhat in time. Haven’t looked up torque specs yet. The Tohatsu 2-cycle Service manual I have says the head gasket goes on dry and the “engine base “ gasket gets coated both sides with high temp gasket dressing. You have a favorite brand Paul? I guess it’s time to work on the parts list and get them ordered. Now to prep for touch up paint. I’m thinking brass wire brush, Total Boat Alumiprep Etching wash, (What I have on the shelf), and high heat black motor paint. Again, what I have on the shelf.i would paint before assembling and again after assembling th seal the gasket edges. Boy, I can make a project out of anything but I feel good about fixing this little motor. Starts first pull every time and deserves the love.
 
Head bolts, 10 to a pack:
9161140630MBOLT (10 MULTIPLE)$1.13

I usually install the newer base gaskets dry.
 
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