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Old 08 November 2011, 09:00   #1
TheMadMariner's Avatar
Country: UK - England
Boat name: SeaRider SR4
Make: Avon
Length: 4m +
Engine: 55HP Yam
Join Date: Mar 2011
Posts: 28
Johnson 55 sea horsie issues

Hey all,

I've got this late 70's Johnson 2 stroke 2 cylinder which I am working on.
I did a testrun on the muffs lately, but the engine won't run at idle at all. It hasn't run in a long time, so I took appart the carbies, cleaned them, and replaced some fuel lines as well. Set both idle & WOT timing and did a testrun on muffs again.

It ran just as worse as before, coughed like crazy, sometimes spit back through the carb's and generally running irradic and smoking a darn lot. Also, the motor keeps leeking this black, oily stuff through the exhaust while running, deff two-smoke oil.
Adjusting carb's didn't do much, the engine just dies out at aprox 1500 RPM everytime, according to the inductive tacho.

Cleaned the carb's once more, and inspected the reed valves manifold as well, but all to no avail.

So the timing is set, carb's are fine, get and hold it's fuel, Reed's are OK and compression seems normal and even on both cylinders. My next guess it's the ccrank lower- or upper seals...any other ideas on this?

Thanks in advance,
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Old 08 November 2011, 11:29   #2
Country: UK - England
Town: NW Surrey
Boat name: Lady Helen
Make: Avon
Length: 3m +
Engine: Out Petrol 3.5 & 15
Join Date: Aug 2011
Posts: 222
The first thing I'd check is that both cylinders are working. Does pulling each plug lead off in turn have the same affect? If not do both plugs have a spark?

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Old 10 November 2011, 05:26   #3
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,650
Yeah, my old Yam 55 2pot ran like a dog with one spark plug slighty degraded. if you have an electrician friend, ask him or her to do a 1000V insulation test on the plugs - you may be surprised just how they break down. if you don't have a friend like that, just change the plugs anyway, it can't do any harm & for an engine like that will be low cost. Also check the HT leads - the older ones sometimes the fittings on the end can detatch themselves form the cable.
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Old 10 November 2011, 14:54   #4
Country: UK - Wales
Town: Here
Boat name: doggypaddle
Make: Avon 5.4 Searider
Length: 5m +
Engine: yamaha 80
Join Date: Jul 2007
Posts: 1,107
Are you sure the idle jets are clear? do the idle screws make any difference?
If its been stood a long time you may need compressed air/soak in carb cleaner/soft wire to clean the gum out.
i even resorted to a twist drill bit sometimes It could be crank case seals, but i would be poking every orifice on the carbs through with wire before jumping to conclusions that involve that much work.
Dont want to teach you to suck eggs, but i have fixed many engine problems by cleaning carbs that have already been "cleaned"
I am usually not as green as i am cabbage looking.
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Old 10 November 2011, 15:11   #5
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Nos4r2's Avatar
Country: UK - England
Town: The wilds of Wiltshire
Boat name: Dominator
Make: SR5.4
Length: 7m +
Engine: Yam 85
MMSI: 235055163
Join Date: Jul 2005
Posts: 12,898
Compression check it with a gauge too if you have one-you won't notice a 30% loss of compression on one pot pulling it over by hand..

I'd be wary of that engine anyway though-they were well known for throwing conrods through the block.
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