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Johnson 60 HP Bad running at 75%25100%25 throttle

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bluefonze

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"Hi, I have recently obtained

"Hi, I have recently obtained a Johnson 60 HP out board, The problem ive got is that the engine starts with no problem then runs ok until about 75% throttle onwards, the motor then hunts violently whilst pouring out smoke, i don't know if it makes any difference but I havent tried the motor in water but i don't want to risk taking the boat out until this fault is solved. The motor has been looked at by 3 technicians all of them replacing a coil which has made no difference, the advance/ retard seems to move freely. Any ideas would be welcome."
 
"Try it on the ramp without un

"Try it on the ramp without unloading the boat, make sure your motor is well under water so you do not run your water pump dry. You may be losing the necessary backpressure needed, or over-revving past RPM limit, causing it to act up. This will be a good test of your water pump and your t-stats as well. Running your motor on the hose forces water into your motor, out on the lake your pump has to pull water in. Thats an important part not to be overlooked."
 
"Sorry if i sound a bit cluele

"Sorry if i sound a bit clueless here but what do you mean when you say the slow system, Cheers.

I will give that a go Kevin Thanks."
 
"As You did not mention which

"As You did not mention which Year or type 2/3 cyl 60 You have a bit difficult to give an excact answer. The 3 cyl has a thermoswitch (brown wire) going into the power pack which limmits the rpm if overheated. This should even set off the alarm if it works. However it may happend that the powerpacks gets 'locked' in slow mode even without overheating. This mostly happends if there is a 'spark' jump into the brown signal wire from the plug wire.
If a brown wire goes into Your powerpack, pull it out and test again. If problem is still there, try to change power pack. Finally be sure You do not have spark plugs (NGK) marked 'R'."
 
"Thanks Morten, I think the mo

"Thanks Morten, I think the motor is a 1988 and it is a 3 cylinder 2 stroke. I will have a look at the suggestions you have made, cheers."
 
"Hi Morten, disconnecting the

"Hi Morten, disconnecting the brown wire has done the trick thanks very much, only thing i need to do now is rectify the problem, is this a power pack or thermo switch problem. thanks again."
 
"Everything may in fact be ok

"Everything may in fact be ok except for Your warning horn that does not give a signal of hot engine! The 3cyl had some different cooling issues around that time.
1:If You have a white type plastic thermostat with a vernatherm inside, change the whole unit to the newer replacement type that does not get stuck in the rubber bushing.
2: Furthermore move the tell tale outlet from the exhaust cover to the top of the engine. (There is another discussion going on (vernaterm .....), check that one out.
3: Check/replace the alarm horn!!!
4: Replace the temp switch if problem still excists!"
 
"Cheers for your help Morten y

"Cheers for your help Morten you have been a star, i will carry out the tests you have suggested. Thanks again."
 
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