Picked Up The Merc!

[fast_boater]

Hey guys, well, picked up the 1980-83 (not sure exact year) Mercury Blue Band 500 50HP. Compression was around 120ish on all cylinders, and there was spark from every wire

I did start it it was rough because it was being stored for 3 years (3 year old gas it started on aswell), so i figure a good carb cleaning and bottom end oil changes it should be just fine.

about the bottom end, when i did pull the drain plug water ran out and then came this really white milky coloured oil but wasnt totally watery still smelt like oil and everything, i didnt think much of it because i figured it went that way from being stored because he never drove it with that oil so i figured it shouldnt have wrecked anything.

Just wondering a good way to flush the bottom end out>? I opened all the drain plugs and poured 10w30 oil through it and let it drain out the bottom until just clean oil came out, but what does the "FLUSH" drain plug do?

How hard would it be aswell to pull the lower half of the bottom end off? How hard to change the impellor? What would also be a good way to make sure all the "gears" are good after sitting with that crappy oil?

How hard is it to rip the carbs off to clean them and how would i do it?

Thanks for all the help i know its long but i hope somebody can help me. I'll probably have more questions in the future thats all i can think of right now.



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[longjohnsilver]

Milky oil means water ingress so you need to change the seals.

The flush drain plug is to enable an attachment to be fitted so fresh water can be used to flush the engine with a hose.

That's as far as my outboard knowledge goes, I'm sure others can help with your questions.

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[rich]

I seem to remember, they have a very high voltage to the plug leads, and strange looking plug electrodes!!!

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[fast_boater]

how and where are the seals that i have to change?

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[Dave_Snelson]

1) The flush plug is there so as you can attach a hose to flush the cooling system with fresh water after use in salty or muddy water.

2) Not only is it desireable, but it is now essential to remove the lower leg to replace the upper and lower water pump drive seals. The reason you have water in the drive leg oil is that the drive shaft that is directly connected to the crank shaft (splined attached) goes through the middle of the water pump and as such turns the impellor. The water pump case has an upper and lower seal these will need replacing, as will the water pump impellor itself.

To do this, you need to undo the obvious looking nuts on the lower drive leg. The two less obvious bolts / nuts are a) the bolt that holds the sacrificial anode (also acts as trim tab) to the leg and there's one under the removable cap as you look down on top above the propellor. These may be one and the same - cant quite remember. The leg will then loosen a little and you then have to lower it as far as you can and detach the gear linkage - don't try to just wrench it. After the linkage has been undone, you can then slide the shaft out with the gear box and propellor attached.

The pump is then visible on the base of the shaft that you have just removed. Remove the bolts that hold the pump case to the gear box (4 I think) and remember where they came from cos they're different lengths and the pump will slide up over the shaft. Hopefully the shaft will be stainless, earlier ones weren't and as a result were useless. Disassemble the pump and it will become obvious how it works.

Check the shaft where the seals run to make sure that the seals haven't worn two circular grooves around the shaft. If they have come back to me for further advice, if they haven't , then proceed with the new parts and reverse my description for reassembly, not forgetting to vaseline the new seals and impellor.

Let us know how you get on.

PS if you come across any mild steel nuts and bolts, replace them with stainles steel ones. Merc had a habit of cutting corners in the 80's

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[Kevin]

Hi

serial numbers starting 5531630 are 1980/ 1981

5949386, 1982

6275323, 1983

they stopped making the 500 in 1978.

I have a complete seal kit for my 1980'ish 80hp mercury that i dont need, not sure if they will fit your 50hp if so you can have the pack, I have no need for them, they are quicksilver part number 26-55682 A1 just let me know and i can post them to you. I know the gearboxes, ratios etc are different but mercury only made a couple of gearbox cases so they still may use many of the same seals.

good luck with the engine, great 4 cylinder with so much torque.

kevin

 

[jfm]

Kevin is right, if it is badged as a "500" then it is 1978 or prior. After that they were badged with the horsepower eg 50. If you post a pic showing the decals, can give you the exact year.

Dave's description on how to fix the water pump and seals is comprehensive, nothing to add. But the reason for the milky oil could also be failed seals lower down in the gearbox, which requires a gearbox stripdown and a special tool to remove the locking nut at the aft end of the gearbox. Taking the gearbox apart really requires the manual, becuase you need to fit shims on reassembly.

The drain plug for the gear oil is magnetic, so if it has virtually no swarf on it the gears may be ok. I'd be inclined to just change the gear oil and the water pump/seals as per Dave's message aboe, then run it for a few hours. If the oil stays dark you are ok, and you have avoided the gearbox strip down which is a big job. Check the oil several times. If if goes milky again you definitely need to strip the box down. If you don't, you are certain to have catastrophic failure before too long.....

Remeber all the nuts/bolts will be A/F, not metric

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[fast_boater]

ok thanks guys. i'm going to try and drop the lower leg off right now, how do i disconnect the shift linkage once i get it to drop alittle bit?

is this a big job? is it hard to replace the seals?

yes it says "500" on the back if the cowling. It sure looks like its newer than a 1978?

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[fast_boater]

ok, got the lower end off, no problem. cleaned it all out, and then i will remove the water pump tommorow. theres no springs that will come shooting out or any little pieces that i will never get back into place again are there?

so what i want is a new impellor, and upper and lower water pump gaskets correct? what would i ask for at the dealer these or, something like "the water pump kit" ?

i was looking for a serial number plate but cant find anything where would i find the serial number?? thanks again,

and by the way, how hard is it to remove and clean the carbs?

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[Dave_Snelson]

Excellent - you've broken the back of the work and yes, you have guessed right in that you require a "water pump kit". This comprises two seals, two gaskets and one impellor. There are no nasty springs that pop out, but to look for the impellor drive pin when you lift the impellor off - don't lose it.

Carbs are a methodical thing - just remove linkages etc and don't adjust them. Unbolt the carbs and disassemble noting where every bit comes from and do one carb at a time. Do not clean out any component with anything metalic. If you do, the carb or its component is knackered. Use plastic scrapers or poking implements to remove any blocked jets or deposits that you see.

If you are unable to see serial numbers, take the water pump to a Merc dealer and he/she will advise. Serial numbers use to be on a little plate below the little cowl thing that says 500.

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[jfm]

a few more details

Just 3 additional points to Dave's comments:

1. The water pump kit may also contain a metal liner for the plastic pump body. It is usually worthwhile changing this too. Reason is, pumps can fail because of poor seal at the flat circular interface between the impellor and the pump body, not just by wear at the impellor blade tips. This kind of failure can be cause by scoring of the metal face, so changing the liner fixes it. To change the liner just prise the old one out and push fit the new one.

2. AFAIR the serial number should be on a silver metal plate rivetted to the starboard side of the casting that attaches to the bit that bolts to the boat transom. See this pic, different model but same era. The serial number plate is the silver rectangle below the lower blue stripe decal. If you can't easily see it, it must be missing. Later models use a plastic adhesive serial number plate, but your 1978 will be a metal plate.

3. When you reassemble take care to get the sense of the gear change right. One way is to put the gearbox into neutral (check by feeling the shaft rotation) and put the selector lever inside the powerhead in the the neutral position (ie halfway), and only then attach the gearbox back onto the leg. Otherwise you can be a step or 2 out on the splined connection of the gear change shaft, and the gears wont select, and you have to take the gearbox off again!

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[Dave_Snelson]

Re: a few more details

What a fine example that 90 is. I used to have one and loved it. Know what made it even better?? - a propellor from Solas (Steel Developments) in London. Went like a rocket. It also had a lovely straight 6 burble on tick over and an even more lovely "Merc 6 Howl" at full throttle.

Happy days...

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[jfm]

merc straight sixes

We bought that one new in 1981 and only sold it 3 yrs ago! Beautiful motor. The merc-6 howl noise was great and unique to this line of motors, it was pretty much all induction suck noise I think because mechanical chatter noise in this beast was pretty much none existent. Yes, happy days!

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[Dave_Snelson]

Re: merc straight sixes

Yes indeed!! All this eco-friendly, make-em-run-quiet stuff is just a pack of crap. If it don't sound like an outboard, then it ain't an outboard. And yes again to the mechanical quietness - virtually no mechanical sound at all.

Mine had a name - "Darth" as in Darth Vader - 'cos a mate of mine looked at the height of the engine and the fact it is nearly all black with that funny front clip on cowl and declared it to be Darth Vader - and from that moment my Merc 6 was affectionately known as Darth.

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[jfm]

two merc 6 saddos - sorry to evryone else

If you have a broadband email address that can take a 2.75meg file let me have it- I have a 25second quicktime movie I can send. Before we sold the motor I took the movie with sound so I could playback the sound!

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[Kevin]

Re: two merc 6 saddos - sorry to evryone else

i personally love these engines i have had a few that ive used and some ive done up and not used,. they do make a unique sound that these newer hairdryer engines fail to match

kevin

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[fast_boater]

Re: two merc 6 saddos - sorry to evryone else

hey guys, you can send me that clip at bjnc@sympatico.ca if you like, i would love to hear it.

found the plate with the serial number. s/n is 4070355. What year is it?

I will order the water pump kit as soon as i find out what year it is. Thanks again, Neil

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[Dave_Snelson]

Re: two merc 6 saddos - sorry to evryone else

Excellent!!!!!!

dave.snelson@btconnect.com

Cheers.

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[fast_boater]

Re: -

well found out from a guy on another forum that its a 1974. Sounds like a good motor hope everything will turn out for the best, going to order gasket set and impellor tommorow. wish me luck.

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[Dave_Snelson]

Re: -

Let us know the outcome, I hope its positive. Look after this engine 'cos a) its good and b) spares are rare.

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