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Old 21 September 2014, 06:01   #1
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Starting old mercury 7.5 hp

Hi all just managed to get hold of a mercury 7.5hp thunder bolt.
Apparently not been started for 20 years. After a quick inspection with my limited knowhow I found that I can pull the start cord but it is very stiff to pull but it duz turn. Any advice on what my next step would be would great thaks
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Old 21 September 2014, 06:15   #2
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Well... if you want to use it, it'd make a good anchor. If you want to sell it, sell it as spares or repairs and let someone else have the inevitable problems that come with a semi-siezed engine.

Basically, if you don't know what to do with a semi-siezed motor, you shouldn't be playing with it as you'll more than likely cause damage that will result in engine failure. It's not a novice's project, no matter how much helpful advice you get.

You may have already caused irreparable damage just by turning the motor over when dry.
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Old 21 September 2014, 06:41   #3
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Nos is probably right but I guess it depends what you mean by "it is very stiff to pull but it duz turn"...
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Old 21 September 2014, 06:59   #4
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I have only pulled it slowly to see if it turns not to try and start it. Just want to know if it is going to be useable.
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Old 21 September 2014, 07:02   #5
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Highly unlikely.
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Old 21 September 2014, 11:58   #6
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Any advice on as what procedures to take first things to check.
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Old 21 September 2014, 12:09   #7
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take to your local marine shop and have them look at it, I know you dont want to waste money noboady does but it could be a cost to save, spend 50 to be told its scrap or 50 could say it's a cracker
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Old 21 September 2014, 13:29   #8
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OK thanks was hopeing for something a bit more constructive but thanks anyway
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Old 21 September 2014, 14:00   #9
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I sent you a PM
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Old 21 September 2014, 14:13   #10
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Originally Posted by tooter View Post
OK thanks was hopeing for something a bit more constructive but thanks anyway
Actually that probably is constructive. No offence intended but without some experience in the area you are potentially more likely to do harm than good (as Nos4r2 has already suggested) and if you had that experience you probably wouldn't be asking here where to start.

Essentially any petrol engine needs the following to run:

fuel and air in the right mix
compression
a spark

all at the right time! The engine has been sitting for 20 yrs, if it was "put away" in perfect running order, winterised before being put away and stored somewhere nice then its feasible to put fresh fuel/oil in it turn it over and off she goes, but if its turned over - even slowly - without oil getting to the cylinders you can cause significant damage, all the more likely with an engine thats potentially been stored badly. Depending how it was stored the carbs may be blocked. If no fuel is getting in, then on an old pre-mix 2 stroke no oil is getting in either.

Assuming the stiffness turning over is not a trivial problem with the pull chord mechanism then its a really bad sign. If the head needs to come off (even to investigate) that is not a "beginners" job especially on an old engine with potentially seized bolts etc.

If its an easy fix 50 ish for an hour of a marine engineer's time and your engine is running. If its goosed then you find out before you've wasted a whole load of money on parts and a several hours of grief working it out for yourself. You'd also be able to sell it for spares/repair with a description of whats wrong which will get you more money than "stiff to turn over".
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