50 hp Merc lower end maint.

I have a '73 50 HP Mercury that needs lower end seals and a new impeller.

I'm looking for guidance on dropping the lower end for access to the impeller. I also need to get access to the prop shaft seals. I've incountered the castellated ring that looks like it holds the guts in. Are we talking special tool here?

 

Yes we are!
The castellated ring is an alloy nut, very difficult to unscrew after all these years.
Dropping the lower housing to replace the impeller is a simple operation, just unscrew the nuts and possibly the Allen bolt under the trim tab.

Then put the gear housing in a large vise, spray penetrating oil and use the pipe tool to unscrew the ring. Sometimes the use of a blow torch is inevitable, ruining the paint and the old shaft seal. Normally I do everything myself, but for this operation I would bring it to a Merc dealer.

 

Yes pay no attention the the Drive shaft and gear selector rod and the water feed pipe.

Take it to a dealer, you will wish you had.

 

Putting it back together again is a different chapter Frosty!

 

frosty has a point. those old mercs don't use a stainless drive shaft and if it has not been apart for a long it will probably be frozen into the crank shaft.

 

Thanks for all of the input guys. I got on another forum and got intell on the 4th bolt. It dropped right off afterwards. I won't tell you about my idiocy, but I did figure out the right place to put in the gear oil. :idea: The impeller was still intact, so I may reassemble for additional running trials. I plan to switch it out, but it got me think about the pee stream that I wasn't getting. Found a clog at the exit. I'll get practice putting it together and I'll check to see if I get water in the gear lube.

 

glad it came apart for you, when the drive shaft gets stuck it turns a little job into a big one. replace the impellor even if the old one looks okay. and put plenty of marine antisieze on the shaft splines before reassembly.

 

Replace the impeller. It's 10 bucks and they die, even if not used and look good. If it's over a year old and has been installed, regardless of hours on it, replace it. Other wise, you'll using a shop vac to suck out all the little broken bits, hoping you got them all be fore you reassemble.

 

A few important points:
- I repeat, renew the impeller.
- When deassembling or assembling do not pull the drive shaft out or lift the leg from it. Unless you know the correct procedure is certainly that way. Reinstalling the drive shaft into the pinion gear and aligning the system requires deassembling the gear case and special tools quite often.
- Do NOT rotate the drive shaft in incorrect direction while installing the impeller into its housing or testing the pump. Ensure that you know in which direction the power head rotates.
- And lastly, do not run the engine without water for the pump.

 

another important point: spend a few bucks on a workshop manual for your engine, they are worth their weight in gold.

 

I knew I would get responses from my comment on reinstalling an old impellor.

I'll contain my eagerness and get a new one. A coworker has given my a line on a knowledgeable and trustworthy shop that I've been doing business with, but it's a bit of a drive so I'm trying to be efficient in my trips up to the shop. I'll track down the impeller at a closer location.

What would be your concerns over a gear case that has sat open for several years (Either stored indoors or hung verically on the transom)? My thoughts are to fill it and run it on the hose and see if I get any leakage. Then, pop a plug and check the oil itself for water and/or debris. Thoughts?

 

the driveshaft cant come out of the gearbox so dont worry about that
Ensuring the gear shift stays in the same place when its off is the only trick
What gear was it in when you pulled it off?

 

I need to shop where you shop. I've called two shops and they both said $25. I want to say bad things about the state I live. I'm sure you get a better rate than I do, but 150% more...

Down to $17.

Powerabout,

It was in neutral and I noted the position of the lower shift mechanism.

 

I got brave and worked the lower water pump housing out. I'm glad I did. One of the shaft U-cup seals had a displaced spring on a portion of the seal. I'll be ordering the whole impeller kit.

While working the housing out and cleaning all of the crud out from around the housing and trying to avoid dropping any into the shaft bearing, I got to thinking about the cleanliness of the gear housing. Is there a flush solution for flushing the housing or is a drain and replentish all that is typically done. I was thinking about engine oil changes and the engine cleaner that you can add just before an oil change. Would there be a similar product for a lower end oil change. Granted, there are no combustion products being dealt with in the gear case.

 

Greg, with Florida being Americas biggest purchaser of plywood and one of the largest marine environments in the USA, we probably have some advantages over you NY'ers.