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Old 05 January 2005, 20:26   #1
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Yet another thread (with the same problem) Engine wont run!!!

Okay... let's start with a new clean slab for 2005

Situation: 1978 Merc 20HP 2 stroke 2 Cil Outboard wont run, history of trouble since we got it..
Now has: new coils, new spark plugs, new spark plug leads..
Healthy spark at right time, seems to be getting fuel ..
Last time it ran *propperly* was on the water when it ran on only 1 cil, then 2 cils and then quit working, and only backfired through exhaust afterwards (and very weak spark) We then discovered both coils were cracked etc.. and now im here!

I managed to get it to run on 1 cil 2 months ago (I've been away and have not touched it since) and it only ran for 20 seconds before cutting out again!

Outboard wont start with choke on, however from time to time it backfires through exhaust... Now here's the thing.. just browsing on outboardrepairs.com i found this:

Q
Hi,
My Force 125 regularly "sneezes" when starting hot or cold,then runs fine,but I wouldn't call mine a backfire

A
Yes, they all sneeze a bit. This is why I quit reccomending Boyesen composite reeds on the 85-150HPs. This sneezing can damage glass reeds.


Sooo... mine has done this "sneezing" quite a few times now.. is what they say about the reed valve true?! If so... how big a job am i looking at.....
And what new bits would i need? Jackets, Gaskets etc.. ?
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Old 06 January 2005, 04:18   #2
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A common problem ive found is that if the mixture is too lean (not enough fuel) at tick over the engine will cough, struggle to idle for a second, maybe stall, but then recover. In most cases adjusting the idle mixture cured the problem, but it sounds like you may have other problems as well.

ATB
Tim.
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Old 06 January 2005, 06:53   #3
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Its 1 turn out (Factory default - supposedly fail safe..)
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Old 06 January 2005, 15:33   #4
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Quote:
Originally Posted by Mr-d
Okay... let's start with a new clean slab for 2005

Situation: 1978 Merc 20HP 2 stroke 2 Cil Outboard wont run, history of trouble since we got it..
Now has: new coils, new spark plugs, new spark plug leads..
Healthy spark at right time, seems to be getting fuel ..


Sooo... mine has done this "sneezing" quite a few times now.. is what they say about the reed valve true?! If so... how big a job am i looking at.....
And what new bits would i need? Jackets, Gaskets etc.. ?
Hi Mr-D

Are the spark plugs wet (to much fuel), you could also try and run the engine with one spark plug removed, then you would be able to see if high speed spark is OK, try both cylinders, this will tell you which one is working

As for doing the reeds on this and many older merc's forget it, as this requires the power head to be removed and engine totaly stripped as the reeds are fixed to the crank. Wot a Bl**dy good idea
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Old 06 January 2005, 16:48   #5
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Quote:
Originally Posted by Ian Austin
as the reeds are fixed to the crank.
Are you sure?
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Old 06 January 2005, 17:24   #6
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Quote:
Originally Posted by jwalker
Are you sure?
Mr Jwalker

Yes, they are in a housing that fits around the centre crank pin.
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Old 06 January 2005, 18:10   #7
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Sparkplugs are not wet, but a bit damp, like they should be I.e. you can smudge the surface and see your fingerprint etc.

Tried running just the one... nothing at all seems to happen if i remember correctly.. no kick.. no backfire..

So.. if a reed was faulty, and it runs through the crankshaft, Let's say cylinder 1 is on compression stroke (and reed is faulty) and cil 2 is on exhaust stroke (also a faulty reed) could that cause the air/fuel mixture to be rammed down the exhaust, ready to be ignited by #1's spark/small combustion?

Im not afraid to take it to bits, but i've just spent (well, my mum has..) 150,- on the new coils and bits..
Are the reeds still available? I have the manual to take it to bits with... but i'd need to know if its worth it! (New parts needed etc.)

If i were to take the powerhead to bits... what new gaskets would i need (and which can i re-use?) Also water jackets etc?

Thanks,
Daniel.
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Old 29 March 2005, 19:21   #8
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Fixed!!!!! Yey!

Right, decided to have another go, however with it sitting still with plugs in, thing seized, refused to pull over, took the covers off etc, stuck a crowbar on the flywheel and rotated it, and the flywheel started rotating without moving the crankshaft... Fantastic... took the thing off, and the key had broken, so made up a new one and stuck it back together, also discovered that *someone* had not replaced the washer on the flywheel, and most likely not used a torque wrench to do it up...

Took the carb to bits again, found out that the idle needle thingymebob was semi blocked, so dipped the whole carb in petrol a few times, blew all the holes through with compressed air, discovered that the fuel diaphrams were (i think) in back to front, gasket leaning on a membrane etc, should have been other way round, also discovered that a spring was missing from the mixture control, i accidently dropped a bolt and started looking for it, and came across this spring that fit beautifully, rusty etc, cleaned it up, stuck it back together... 3 pulls with choke on, and it fired, choke off, first pull.. it works!!! then i forgot that the oil would have settled/devided in the tank so the engine stopped (at idle). sorted that, now 1 pull with choke on, thing fires up first pull, quickly push choke off, and it runs! it seems to run on 2 cilinders... now it needs a proper run......(and re-adjusted)

Got transom + oars revarnished/reslapped with varnish, going to launch her tomorrow and see if it truelly does work.... the weather is getting better, moved the mooring a bit today, tubes are inflated, thing is on back of a flatbed trailer (dad is using the boat trailer), tractor is hooked up to the trailer, ready to go for tomorrow... except i might have to get up early to try (tides etc) so dont know if i'll wait till night.. tide should be in ~10- 10:30 far to early!

Many thanks for your efforts to help etc.
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Old 30 March 2005, 03:28   #9
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Congratulations! Hope all goes well with your first outing.
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Old 30 March 2005, 06:25   #10
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Louise, you're far too nice.

Mr-d, about feckin time.

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