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My yamaha 30 1990 3 cyl 2 stroke will run perfectly when i first start her up but after about 2 mins at full speed it will slow down to about quarter revs and will not pick up again unless you switch the engine off for 10 min.P.S IF I put the engine in neutral it will rev up the whole range with no problems whatsoever.Any ideas !!!!
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quicksilver,
Check the fuel line bulb when this happens - if it is not firm and has collapsed, then the fuel tank is not venting properly and creating a vacuum and the motor is starving for fuel.
Also, the outboard could be going into rpm reduction mode due to overheating - check the cooling system.
Good luck,
Ken K -
hello ken,i have checked the fuel bulb and the water cooling is running perfectly.
I have even tried disconnecting the thermal cooling switch on the cylinder head but the problem is still there.Comment
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quicksilver,
Sure sounds like fuel starvation problem, but I don't know why it would be thermal related
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Get the boat back out on the water and run it full speed until the symptom reappears. At that point, have someone pump the primer bulb to see if the rpm kicks back up - if it does, then I would suspect bad fuel pump. If the rpm does not come back up, then I would suspect carb problem.
If it has been at least three years since last carb overhaul, then it is about time. I would at least remove the jets and squirt carb cleaner into the orifices. Inspect the ends of the jets - replace any distorted or cracked o-rings. Get yourself a Yamaha shop manual to guide you along.
Good luck and let us know how you come out [img]smile.gif[/img] ,
Ken KComment
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I was wondering if you have solved your problem yet
because i too own a 30hp and am currently having full throttle loss of power problems.
I have cleaned all the carbs,changed tanks and hoses,rebuilt fuel pump,changed plugs but still this problem exists.
Please reply if you managed to fix your situation.
Thanks,GordComment
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