Mercury 850 Shaft seal without removal of shaft?

[67Mustang-man]

So is it possible to remove the shaft seal without removing the shaft, I picked up a 76 MonArk McFast and I worry the shaft seal maybe bad, it has 400hrs on it, the lower unit was empty and the prop has grease on it. I do not know if this is from being a 2stroke or not. Also does the oring on the bearing carrier go bad?

It maybe empty for storage or replacement but unfinished because someone else was working on it and and the electrical issues were above there comprehension.

 

[emckelvy]

Propshaft seal leaks are far less common than driveshaft seal leaks. It probably has grease on the seal because they greased the propshaft to keep the propeller from seizing on the shaft.

The L/U might have been drained for layup and they forgot to refill the oil. If you're really worried about it, you could take the boat to a marine repair shop where they'll have the proper test equipment to do a pressure and vacuum test on the lower unit.

Otherwise, you could just refill the L/U gear oil, run it and see if there are any external leaks or water intrusion. If you have a big problem, you'll know after the first time out.

You can get Hi-Vis marine-grade gear oil cheap at Walmart. Get the quart bottle and pick up the marine hand pump that screws into the bottle. It'll have a threaded adapter that screws into the drain hole of your lower unit. This makes it far easier and less messy to refill.

When you refill, pump oil into the drain hole until it runs out the upper (vent) plug. Replace the vent plug first, then the drain.

After running, just pop the drain plug and check the oil for water; if you see any water freely running out, or anything other than clean oil, time to take the L/U off for service.

HTH.............ed

 

[67Mustang-man]

The L/U being drained for storage was something that had crossed my mind. I will pick up some oil today fill it up and check everything as you said.

Maybe you can shed some light on something else, I noticed my outboard motor is unfused is this normal?

Thank you
John

 

[Texasmark]

I have dug/picked out prop shaft seals on a lower unit the size of the 850. There are 2 placed in front to back to seal in both directions. You didn't say which shaft but it appears that you are talking about the prop shaft. Run your testing as mentioned and then worry about the seal.

Not a good idea to not fuse 12v. Follow the red wires from the input terminal of the starter solenoid which serves as a distribution post besides sourcing power for the starter through the solenoid. Back then your fuse is probably in an inline fuse holder that you grasp both halves and turn CCW about 1/2 turn to get the holder open. Fuse would probably be a SAE or AG 20 amp glass cylindrical housing about 1" long with metal caps at each end, fast blow which means a flat thin strip of metal. Today the fuse is visible and inserted at right angles to the wire in a black water tight holder, color coded for amperage besides being stamped with it.

 

[minuteman62-64]

There are a couple of Youtube videos showing how to pull and re-install prop shaft seals without pulling the shaft. Involves a slide hammer with a vice-grip attachment and some sheet metal screws. I tried it on my drive shaft seals (didn't need to there, just wanted to see if it worked), and it worked fine.

 

[67Mustang-man]

I have dug/picked out prop shaft seals on a lower unit the size of the 850. There are 2 placed in front to back to seal in both directions. You didn't say which shaft but it appears that you are talking about the prop shaft. Run your testing as mentioned and then worry about the seal.

Not a good idea to not fuse 12v. Follow the red wires from the input terminal of the starter solenoid which serves as a distribution post besides sourcing power for the starter through the solenoid. Back then your fuse is probably in an inline fuse holder that you grasp both halves and turn CCW about 1/2 turn to get the holder open. Fuse would probably be a SAE or AG 20 amp glass cylindrical housing about 1" long with metal caps at each end, fast blow which means a flat thin strip of metal. Today the fuse is visible and inserted at right angles to the wire in a black water tight holder, color coded for amperage besides being stamped with it.

Yeah there is no fuse on my system and does not show one on the wiring harness, or schematic for a 1976 Mercury 850. Everything tells me mains should be fused at the battery for safety. I have two 6 Gauge wires and no fuse smells of disaster if some how the wires short out is all. I know these things do not have much for a charging system. While I know this is just a older bass boat I have a 45watt solar panel and charge controller.

 

[emckelvy]

None of the older Mercs had fuses (at least none that I can recall !). Most "modern" outboards do. I wouldn't recommend trying to retrofit a fuse to an older Merc outboard unless you really know what you're doing. IHMO there's no real need for it, anyway.

HOWEVER, all of your boat's lighting, instruments, pumps, stereos, etc etc should be fused and you can connect an extra fused line at the positive terminal of the battery and use that to feed all the aux systems. Most boats nowadays would have something like that already installed.

HTH.........ed

 

[67Mustang-man]

Actually adding one for me one would not be hard, I am very good with wiring but telling me the older ones did not have it tells me I'm sane. I know these engines do not have much for output power on them, this is why I will have the solar panel as well. Thank you for your help.

 

[Texasmark]

Adding a fuse is a no brainer. Cut an otherwise good wire in two pieces and stick it in. 20 amperes is what new ones use and it's a little heavy if you ask me for the size wiring. O'Reilley's has them with pigtails and all plus the waterproof crimp terminals you set with a crimper and heat gun (separate package). The purpose of a fuse is to protect the insulation on the wiring if a short develops which would force more than the design current through a conductor, heating it and as a result melting the insulation. A wiring harness with a wire or more with melted insulation is a mess and you can have two over heat and touch creating a new short ckt.

The power comes from the battery..............same size as in today's engines.

Side question, does your decal on your engine cowl consist of 3 parallel lines that terminate headed down at the rear of the cowl, colored red, blue, and silver with the name mercury spelled with a lower case m? I had an 850 I bought new back then and it was decaled like that. Sweet running, easy starting, maintenance free engine.

 

[67Mustang-man]

Sorry for the delay Texasmark, my decals look like the link below, The motor once warmed up starts with no issues, it takes a few cranks when cold, hold fast idle for a min to warm up but then runs pretty nice.

http://www.mercurydecals.com/outboard/mercury/mercury-1976-85-hp-decal-set.html