Starting old mercury 7.5 hp

[tooter]

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

[Nos4r2]

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.

[Poly]

Nos is probably right but I guess it depends what you mean by "it is very stiff to pull but it duz turn"...

[tooter]

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.

[Nos4r2]

Highly unlikely.

[tooter]

Any advice on as what procedures to take first things to check.

[slate1234]

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

[tooter]

OK thanks was hopeing for something a bit more constructive but thanks anyway

[bartiny]

I sent you a PM

[Poly]

Originally Posted by tooter

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".

[Nos4r2]

Originally Posted by tooter

OK thanks was hopeing for something a bit more constructive but thanks anyway

The thing is, we can go through lots of what you'd like to be constructive advice, but what it boils down to is this:-

You need that motor to work, every time. If it doesn't, you may be in deep deep trouble.
Your 1st post basically asks for advice for a novice on doing a job best left to the experts, on repairing a long neglected, partially siezed piece of equipment that could have any number of other faults from being left standing.Plus you will be relying on it to get you home.

It's worth paying an outboard shop to spend an hour on it to see if it's worth doing. They'll tell you if it's scrap or not and should be able to tell you what work actually does need doing to it.

Realistically, I'd expect the motor to need a full strip and inspection to work out what's stiff,an internal clean, new gasket set , plus a new impeller, plugs and gear oil. That's nearing the cost of a running motor-before you even add in the cost of replacing broken bolts etc and some labour.

[Mollers]

Originally Posted by tooter

OK thanks was hopeing for something a bit more constructive but thanks anyway

By ''constructive'', did you mean 'false hope'?

You've had the best advice, delivered without flowers and frilly bits around the edges.

[tooter]

OK no prob thanks to all for replying.

[Bigmuz7]

We used to have one of those when I was a boy .. I'm now 47 .. the electrics were a constant problem .. I think the advice you've had is good ..

[Searider]

Have got one of those in my dad's garage too. Last run about 1994 I reckon!

[willk]

Originally Posted by Searider

Have got one of those in my dad's garage too. Last run about 1994 I reckon!

LOL - reckon he's flogged it to make space!

[Searider]

Back to the ops question - because I might dig the engine out of the garage and see if it runs.

Bearing in mind the engine is worthless - what should I do prior to trying to start it?
Oil down the bores?
Extra oil in petrol and then turn over with plugs disconnected?
Or stick some fresh fuel in the can and fingers crossed.

It was a rattle smoky thing at the best of times but might be a bit of gun on the river!

[bartiny]

Originally Posted by Searider

Back to the ops question - because I might dig the engine out of the garage and see if it runs.

Bearing in mind the engine is worthless - what should I do prior to trying to start it?
Oil down the bores?
Extra oil in petrol and then turn over with plugs disconnected?
Or stick some fresh fuel in the can and fingers crossed.

It was a rattle smoky thing at the best of times but might be a bit of gun on the river!

IMO a very sensible answer, more or less what I advised him via PM except for the fingers crossed 1

[slate1234]

I had the same engine I found it very hard to link and sync, I sold for parts in the end, while you have the plugs out I would start with a compression test (leave one plug in) before trying to start it if the compression is good (should be around 90-100psi ish) and both cylinders are within 10% of each other go from there.

[tooter]

OK thanks. The engine seems in quite bad condition I'm having trouble removing the top cowling it seems the latch is rusted on not going well at the most.