1969 Merc 500 - 50 hp

A

alyaz

Cadet
Joined
Jun 18, 2013
Messages
13
hi gang. did some searching but would like to clarify some points. just picked up a 1969 Merc 500. it's a 4 cyclinder, 2 stroke, 50 hp engine.

the older gent that had it said he hadn't run it in over 15 years. it started right away but no water was coming out of the 'pee hole' other than a few drops. so we shut it down.

i have taken the lower leg/gear case off and thought i would change out the impeller etc.

the impeller (i will still change it out) was in good shape, not torn etc., and seems to have been installed in the correct direction. so guess some of my questions are:

1. this engine does not have a thermostat correct? i can't see one anyways - and from what i read thermostats only started around the '76 models?
2. should water be expelled from the 'pee hole' on idle, or only when revved?
3. i have blown through the water tube and can hear air escaping but it does not seem to blow out of the 'pee hole' when blowing from below and when blowing in the tube from above it does not seem to be coming out the water tube that goes to the impeller housing. (hoping the power head doesn't have to come out to check fittings there).
4. when draining the oil from the lower case, there were no washers on either the fill screw or on the drain screw... there should be washers on both, shouldn't there?

thanks...
 
gm280

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,593
Re: 1969 Merc 500 - 50 hp

alyaz said:
hi gang. did some searching but would like to clarify some points. just picked up a 1969 Merc 500. it's a 4 cyclinder, 2 stroke, 50 hp engine.

the older gent that had it said he hadn't run it in over 15 years. it started right away but no water was coming out of the 'pee hole' other than a few drops. so we shut it down.

i have taken the lower leg/gear case off and thought i would change out the impeller etc.

the impeller (i will still change it out) was in good shape, not torn etc., and seems to have been installed in the correct direction. so guess some of my questions are:

1. this engine does not have a thermostat correct? i can't see one anyways - and from what i read thermostats only started around the '76 models?
2. should water be expelled from the 'pee hole' on idle, or only when revved?
3. i have blown through the water tube and can hear air escaping but it does not seem to blow out of the 'pee hole' when blowing from below and when blowing in the tube from above it does not seem to be coming out the water tube that goes to the impeller housing. (hoping the power head doesn't have to come out to check fittings there).
4. when draining the oil from the lower case, there were no washers on either the fill screw or on the drain screw... there should be washers on both, shouldn't there?

thanks...
Click to expand...

First things first... Welcome to iboats :welcome: glad to have you aboard :focus:

Being how the engine sat for 15 + years I would expect the impellor has a set and not pumping water very well. I would try some pressurized air in the water tube and see what happens. Could be a blockage further in the cooling system (some bugs and/or insects will do that). As for the two fill and over-flow screws, some types use an "O" ring instead of a seal or gasket. And those "O" rings can get flattened to be almost invisible. Check the heads of the two screws and see if there is flattened "O" rings there. You can purchase new ones ("O" rings or seal/gaskets) when ordering the new pump impellor and seals for the lower foot. Also, if you are running this with muffs it could be that the muffs are not covering the openings correctly and therefore water isn't circulating OR if you are running this in a barrel (or something similar) make sure the water is filled up enough to cover the water pickup openings. Just some ideas...
 
A

alyaz

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Joined
Jun 18, 2013
Messages
13
Re: 1969 Merc 500 - 50 hp

gm280 said:
First things first... Welcome to iboats :welcome: glad to have you aboard :focus:

Being how the engine sat for 15 + years I would expect the impellor has a set and not pumping water very well. I would try some pressurized air in the water tube and see what happens. Could be a blockage further in the cooling system (some bugs and/or insects will do that). As for the two fill and over-flow screws, some types use an "O" ring instead of a seal or gasket. And those "O" rings can get flattened to be almost invisible. Check the heads of the two screws and see if there is flattened "O" rings there. You can purchase new ones ("O" rings or seal/gaskets) when ordering the new pump impellor and seals for the lower foot. Also, if you are running this with muffs it could be that the muffs are not covering the openings correctly and therefore water isn't circulating OR if you are running this in a barrel (or something similar) make sure the water is filled up enough to cover the water pickup openings. Just some ideas...
Click to expand...


copy and thanks for your reply.
 
B

beerfume

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Joined
Dec 14, 2011
Messages
15
Re: 1969 Merc 500 - 50 hp

hey I just posted almost exactly the same scenario, see the posting "re-routing the pee hole" for some excellent answers!
 
brnschoneck

brnschoneck

Petty Officer 1st Class
Joined
Feb 22, 2013
Messages
337
Re: 1969 Merc 500 - 50 hp

also u may wanna do fuel pumps and check fuel lines especially if it was stored outside ...there easy insurance and cheap ..clean carbs or ur gnna have problems shortly after ur up and running ...
 
T

turtles11756

Petty Officer 1st Class
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Dec 5, 2007
Messages
260
Re: 1969 Merc 500 - 50 hp

the water will begin to flow out of pee hole maybe ten seconds after start up at idle. run a thin piece of wire up tube after it does to fully clear it. . no thermostat. touch the engine block after you are running it should not feel hot be careful by the flywheel and you should use a new gasket each time on lower unit vent and fill holes when you change gear lube .check all wiring and see if it's falling apart
 
GA_Boater

GA_Boater

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Messages
49,038
Re: 1969 Merc 500 - 50 hp

On the fill/vent screw seals, sometimes they are stuck to the housing and are almost invisible. Something to check.

I hope you changed the impeller. My motor starts to pee if it's cranked for about 10 seconds in a barrel. Less if it starts right away. I never use muffs, bought a cheap plastic tub a Wally World.
 
A

alyaz

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Joined
Jun 18, 2013
Messages
13
Re: 1969 Merc 500 - 50 hp

Yes put a new impeller in and changed the gear oil and located new gaskets for the drain screws. Will start it up later today to see if anything has changed.

Just so I understand... the water enters the leg vents, is moved/circulated up to the power head - is there a plenum of some sort that the water enters to keep the engine cool - before it exits the pee hole?

Have put a piece of monofilament line into the pee hole rubber line and all seems clear.

What do you suggest is the best way to clean the carbs - do they have to come off or will a good carb cleaner work okay?

Thanks guys...
 
dOb

dOb

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Messages
244
Re: 1969 Merc 500 - 50 hp

I have the same motor, only 1974 model. I wouldn't trust a carb spray to do much good. I suggest that you take the carbs off, disassemble, and soak in a can of chem-cleaner over night. Buy a couple (two carbs) of carburetor repair kits and replace all gaskets and seals. After 15 years you might as well go ahead and replace the floats and needles as well. Since you'l be taking them apart, it'll be just as easy to reassemble with new parts. That'll be one less thing to worry about.

I get a constant dribble of water on the muffs. But I get a much more steady stream in the lake.

BTW - I wouldn't run the RPMs too high on the muffs.
 
A

alyaz

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Joined
Jun 18, 2013
Messages
13
Re: 1969 Merc 500 - 50 hp

dOb said:
I have the same motor, only 1974 model. I wouldn't trust a carb spray to do much good. I suggest that you take the carbs off, disassemble, and soak in a can of chem-cleaner over night. Buy a couple (two carbs) of carburetor repair kits and replace all gasketos and seals. After 15 years you might as well go ahead and replace the floats and needles as well. Since you'l be taking them apart, it'll be just as easy to reassemble with new parts. That'll be one less thing to worry about.

I get a constant dribble of water on the muffs. But I get a much more steady stream in the lake.

BTW - I wouldn't run the RPMs too high on the muffs.
Click to expand...

Thanks. :)
 
A

alyaz

Cadet
Joined
Jun 18, 2013
Messages
13
Re: 1969 Merc 500 - 50 hp

Just an update. The new impeller now pumps water out the 'pee hole' even with just the muffs on. Into the water it goes... :)
 
A

alyaz

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Joined
Jun 18, 2013
Messages
13
Re: 1969 Merc 500 - 50 hp

Hope not to jinx anything, but we put the boat in today and it runs great! WTF? Thanks for everyone's help.
 
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