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Old 27 May 2013, 17:18   #1
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yamaha 55 outboard 2 stroke problem , no power when in the water and unburnt oil

hi
i have a yamaha 55 2 stroke on my lencraft, the outboard is from around 1992 the model number is 663 , 55 bed L. when i start her up and run her in the yard she runs like a dream no issues, cooling perfectly and reving up no problem . But when i bring her down to the sea again she starts no issue but when i put her in gear she wont run any faster than idle and a gloopy oil slowly seeps from the exhaust, she is also seems to remain in gear.
can any one help ? i have had her with my mechanic who is at aloss as to what could be the problem
any help
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Old 27 May 2013, 18:10   #2
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That's a 3 cylinder engine, right ? Have you checked all fuel related items : internal tank filter, hose, engine fuel filter, all must be inmaculate clean. Place a small container, purge main tank to outter fuel connector, keep engine connector small ball pushed open with a pin, pencil, whatever. Fuel flow should exit with good volume when priming bulb.

If all ok, sometimes testing with a new fuel hose can make wonders, probably internal small o'rings located insisde fuel connectors could be worn, dried out, sucking air in and engine performing badly specially at non idle throttle settings. Are plugs the correct ones and well gapped ?

Are carbs inmaculate clean, how about fuel pump condition ? You could have a balloned, dried out diaphragam no working properly when engine needs to collect more juice. You could have a dried, hardened faulty head gasket too.

Could have a separate ignition coil failure. One cylinder misses or a CD internal issue when engine is at load too. Will need factory electrical parameters to check them out. Or swap parts, the fastest way to detect electrical failures, but not cost effective though.

That's a 21 year oldie, probably could have developed any of the mentioned age issues which definitely gives troubles. That engine seems needs a full preventive maintenance...

Happy Boating
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Old 27 May 2013, 18:44   #3
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darragh - not my area of expertise but a couple of extra q's which might help those in the know to diagnose:

"when i put her in gear she wont run any faster than idle"

Does it stall, or just not rev? does the throttle move but nothing happens? does the noise go up?

"gloopy oil slowly seeps from the exhaust"

can you explain. can you tell if its unburnt 2 stroke oil or gear box oil etc. is this after you pull her back out?

"she is also seems to remain in gear. "

do you mean it doesn't go back to neutral?
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Old 27 May 2013, 19:10   #4
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Loco,

It's a 2 cyl, runs premix and no CDI to speak of! (I had a 663 a while ago)

Fact it runs Ok on muffs makes me think it might just need the idle screw cranked up a bit - once the exhaust is under pressure it creates enough resistance to slow things down.

As Loco says, you might have an ignition problem - a 2 cyl 2 stroke will barely run on one.

Best bet - check your spark (spark testers cheap form any auto factor), then check your fuel mix. Those things idle like at idle at the best of times......

Welcome to Ribnet by the way!
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Old 27 May 2013, 23:29   #5
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Yep,what 9D280 said- and chuck a new set of spark plugs in as a starting point.
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Old 28 May 2013, 04:51   #6
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Wot Nos said.

(And I just realised it was late & I muissed out an entire lump of sentence! (never edit text when half asleep!) It should have said "Idle like a bag of spanners sitting on a rough thing on a bad day"

Definetly a "WOT" machine those.
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Old 18 June 2013, 11:10   #7
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oil is leaking from the gear box it seems

Hi all
thanks for all your help , we did all you suggested and launched the boat and unfortuantley still no power when you give her trottle
we have taken engine apart down twords the prepeller and it seems the metal casing of the water pump is craked and although the water i spumping perfect this is where we believe the oil is coming from the gear box.
so i believe now i need 2 water pump gaskits and the metal side of the housing for the waterpump, im in ireland but im told the cheapest place to buy these parts is in the usa, does anyone have any supplier they would recommend
The engine is a yamaha 55, the year is 1998, the following detail is on the plate on the engine :nominal power 40.5 kw , mass 89 - 99kg, model 99, 697-84.
on another plate it states : 55BED ,L 331350, U, 663 ,
please excuse my inexpierience on these forums -first time but i really appreciate your help
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Old 18 June 2013, 11:26   #8
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Quote:
Originally Posted by Poly View Post
darragh - not my area of expertise but a couple of extra q's which might help those in the know to diagnose:

"when i put her in gear she wont run any faster than idle"

Does it stall, or just not rev? does the throttle move but nothing happens? does the noise go up?
When in gear i put her in gear in the sea she cant increase the revs even though the the throttle does physically go up but out of gear she will increase in revs
"gloopy oil slowly seeps from the exhaust"

can you explain. can you tell if its unburnt 2 stroke oil or gear box oil etc. is this after you pull her back out? it now seems this is gear box oil.

"she is also seems to remain in gear. "

do you mean it doesn't go back to neutral?
yes it unfortunately is now not going into nuetral with out difficulty
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Old 18 June 2013, 11:56   #9
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Best way to check your gearbox - open the drain hole & see what pours out - if it's oil, there isn't a problem, if it looks like mayonaise to a greater or lesser extent, you have a problem. Somewhere under that water pump plate is an oil / water seal. A cracked water pump housing shouldn't allow water into the oil, but should reduce your cooling flow....

As for the no power, Take a small flat blade screwdriver out with you, to slowly up the idle mix screws on the two carbs (going from memory here - might just be a single carb & a cross head?). Anyway, one test to check your idle mix is open the throttle in gear. If it has a lethargic lack of response, blip the choke, it will then either cough & die or take off like the proverbial scalded cat.

If the latter, your idle mix is not set correcly for the submerged exhaust. (too much back pressure, so whe ntyou open the throttle it can't exhaust with enough force to push the fumes out against the water pressure. (even although it;s only a few inches below the surface) Net result, the cyl doesnlt clear, and the next spark is trying to burn a high proportion of soot from the previous cycle instead of a nice cleam air fuel mix.

So, if it takes off, pull the manual (or post here) to to find the idle mix screw. Memory says 1& 1/8th turn from fully in as a start point, but that may have been my old Suz so check if nobody posts to correct me...
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