Found my old Mercury 7.5HP Outboard today

RIN

RIN

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In the back of the garage. Hasn't been used four 4 years. I am going to try and start it tomorrow. It would be ridiculous to expect it to start so has anyone got any suggestions for things I can try to coax it into life? It's a two stroke.
 
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- Drop some 2-stroke oil down the spark plug holes, and make sure it turns over freely
- New spark plugs
- Fresh fuel
- New impellor
- WD40 sprayed around key electrical bits, check wires etc.

See what happens!
If it works, change the lower unit oil too.
 
an old merc 2 stroke... oh lovely.. what age?

The first thing that I would do is take the spark plug out and put some penetrating oil in the cylinder and let it sit for a day. See if the motor will turn over, if it is stuck and will not turn put more penetrating oil in it. Don't try and force it or you may break a ring and you don't want that. Take a look at the carb, probably a quick strip & clean & rebuild wouldn't do any harm.. drain old mixed fuel out and replace, buy a new spark plug, and have a go.... if it runs great, if not put new points and condenser and you should be in good shape. Impeller will need renewing, do check the tell tail (assume you will be starting in a big bucket of water or the like?)

tell us how you get on. :)


edited bit;
sorry, bit late but at least you are getting the same advice twice!!
 
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Firefly625 said:
an old merc 2 stroke... oh lovely.. what age?
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totally agree.......& yes what year ?

7.5s built 1979 > 1985., 75s ( 7.5 ) built 1967 > 1987. which is urs ?

you may not need new plugs, I am still running my 1976 Merc 500 on the original spark plugs...........and would go with the rest of the advise. Hope all go well & do let us know.
 
Not sure how old it is. We bought it second hand in 2001 as a "get you home" engine for our old bayliner and never did use it much. It has 7.5 on the side but no "s" It has two cylinders, no kill cord, I think you can track the age from the serial number so I'll have a go at that. It's currently mounted on a beam supported by two aluminium ladders and is sitting in our dustbin full of water in front of the pattio windows and SWMBO wants it moved. Now.

Will report back tomorrow evening
 
If it were mine I'd give it some fresh fuel and see if it starts. I have an old Yamaha 2 which sat in the engine room on my old boat unused for over 2 years. When I finally took it out it started 2nd pull, didn't even change the petrol. Now in my garage, been there 3 years, might give it a look today, expect the same result.
 
longjohnsilver said:
If it were mine I'd give it some fresh fuel and see if it starts. I have an old Yamaha 2 which sat in the engine room on my old boat unused for over 2 years. When I finally took it out it started 2nd pull, didn't even change the petrol. Now in my garage, been there 3 years, might give it a look today, expect the same result.
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mmm yes I would expect that from a Yami... but these Merc's take a little more tinkering... (IMO) :rolleyes:
 
RIN said:
It has 7.5 on the side but no "s" It has two cylinders, no kill cord, I think you can track the age from the serial number so I'll have a go at that.

Will report back tomorrow evening
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post or pm me the serial No. I have a list that covers most Mercs or a photo of the decals as I also have a decal list for engines upto 1985.


example
added.... 1985 decals 7.5hp

84a67ab5.jpg
 
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fuel and spark, spark and fuel....

I agree with most of the posters, but wouldn't put penetrating oil in the plug holes of an unseized engine.

Remove the plugs, fit them on the leads and get someone you hate a bit to hold them against the block while you briskly pull the cord. ( Probably how morris dancing was invented-)

Got two sparks? Pour a table spoon (not my tablespoon!) of petrol or 2 stroke into the plug holes, replace plugs and try to start, no choke at this stage.

It'll cough and run, as it dies, apply full choke.

Have full and enjoy exercise, you will warm up first? (not the motor...)

My 'best' one was a 6hp Perky my son found in a neighbour's hedge. Both coils crusty/dusty (ie dead) so we ran it off two 12v car coils and a non charging car battery...

Did Coniston fine!

Nick
 
Tremlett 15 said:
post or pm me the serial No. I have a list that covers most Mercs or a photo of the decals as I also have a decal list for engines upto 1985.


example
added.... 1985 decals 7.5hp
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A decals database! Very impressive. I could do with that; I rely on creaky old memory

I know I'm telling you how to suck eggs but serial # is sometimes better than decals as some decal sets lasted a few years. Thse brown bands were 84 & 85 iirc. The blue bands before then (1980 onwards) also lasted a few years though they made other tweaks to the blue band years (non decal things) to enable geeks to spot the different years
 
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RIN said:
In the back of the garage. Hasn't been used four 4 years. I am going to try and start it tomorrow. It would be ridiculous to expect it to start so has anyone got any suggestions for things I can try to coax it into life? It's a two stroke.
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I once had a 4hp Yamaha that was left unused and unwinterized etc for 5 yrs.

I thought it would have seized but a gentle pull of the cord showed that the piston was free and there was compression. Oh! lets see i thought.

Turned on the fuel - full coke and swished the engine about a bit. One tug on the cord and she was away! Fab.
 
Tremlett 15 said:
post or pm me the serial No. I have a list that covers most Mercs or a photo of the decals as I also have a decal list for engines upto 1985.
Click to expand...

Tremlett
the serial no is 9236651, made in Belgium. Its black with grey / red stripes on the side with "MERCURY" in white capitals. It has a white 7.5 at the back.

Just off now to get some 2 stroke oil. 2% mix I think isn't it?
 
jfm said:
A decals database! Very impressive. I could do with that; I rely on creaky old memory

I know I'm telling you how to suck eggs but serial # is sometimes better than decals as some decal sets lasted a few years. Thse brown bands were 84 & 85 iirc. The blue bands before then (1980 onwards) also lasted a few years though they made other tweaks to the blue band years (non decal things) to enable geeks to spot the different years
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Thanks....... yes decals are only a "guide" if serial Nos are missing, as some styles cover more that one year

1955 > 1967 " white/silver/wee bits of red etc" bands

1968 > 1971 red bands

1972 > 1983 blue bands

1984 & 1985 brown bands......may info ends here!!!!


after 1985 no longer "classis" ( ha ha )
 
Update Thursday 11.45

Update at 11.45 The good news, the engine started and ran smoothly after putting a squirt of fuel into each cylinder. However no sign of the cooling water exiting the outboard so I switched off. Should I run it for a few minutes to see if the water comes through or should I start looking at the impeller? Any idea where it is?
 
RIN said:
Tremlett
the serial no is 9236651, made in Belgium. Its black with grey / red stripes on the side with "MERCURY" in white capitals. It has a white 7.5 at the back.

Just off now to get some 2 stroke oil. 2% mix I think isn't it?
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oil mix I think would be 50:1

having a wee problem with ur serial No. my lists are giving 9181726 > 9461525 as 1978 > 1984, most serial Nos "bands" are for one year, with the odd double year, will need to have a closer look, must get back to that "work thing" but will have a look later. Good luck with the run.
 
RIN said:
Update at 11.45 The good news, the engine started and ran smoothly after putting a squirt of fuel into each cylinder. However no sign of the cooling water exiting the outboard so I switched off. Should I run it for a few minutes to see if the water comes through or should I start looking at the impeller? Any idea where it is?
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How long did u run it for & when last used, was it sea or fresh water ?

If you need to renew the impeller, I can pm/email you a page from the service manual for you to replace the impeller yourself, ( most of my manuals cover a "band of years" )
 
Start by checking that the telltale is not blocked (insects or spiders nesting). Poke out hose and fittings at both ends or blast through with compressed air.

You can afford to run it without a water flow for a few minutes but not beyond the point at which the cylinder head is to hot to keep a finger on for a few seconds.

If telltale clear and no water flow within a minute or so then pump impeller is the next stop.

BTW you will find a year identifier HERE
I make it a 1979 model

and owners manuals to download from HERE
 
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