Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

[JohnMartin]

I've go a 1997 model Johnson Ocean Runner V4 115hp two stroke outboard which vibrates violently and loses power at any attempt of giving it some throttle. It seems like the engine gets and loses power in a high frequency, which results in loss of general power combined with vibrations. At idle the engine runs smoothly. Please see the following video for a description of the problem: http://www.youtube.com/watch?v=Ghtwn8RTUI0&feature=youtu.be

This is what we have tried until now:
- Changing spark plugs
- Draining carburettors
- Cleaning fuel filter
- Adding condensation water removing liquid to the fuel

If anyone has an idea of what the problem could be, or knows of anything more to check on the engine I would really appreciate your help

 

[Chris1956]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

Sounds like the SLOW system is being activated. Is the motor overheating? Check spark to all 4 cylinders. If one bank has no spark, maybe the slow system is the culprit.

 

[JohnMartin]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

Sounds like the SLOW system is being activated. Is the motor overheating? Check spark to all 4 cylinders. If one bank has no spark, maybe the slow system is the culprit.

Thanks for the answer! I will check the spark in the spark plugs. The problem occurs even if the engine is not run warm before giving it throttle, so I doubt the problem is overheating. Could you please explain briefly what this SLOW system is?

 

[boobie]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

Get an open air gap spark tester, set it to 7/16 " and then check your spark. As a big guess, you could have a bad powerpack or osi sensor.

 

[Chris1956]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

The SLOW system is an automatic killing of the spark to 1/2 the motor, if the motor thinks it is overheating. The two overheat sensors are connected to the powerpack via a blocking diode. If the sensors think the motor is overheating, they ground and send that ground signal to the powerpack. Disconnect the temp sensors and see if the motor runs normally. If so, test the temp sensors and wiring.

 

[Haffiman]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

It may even be a case where the powerpack itself has 'locked' in SLOW modes if it happens without temp switches connected. If engine gets warm, alarm should be activated as the SLOW kicks in and the Temp light on the sys check tach/instrument light up.

PS: Which plugs are you using?

 

[JohnMartin]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

Thank you so much for the answers!

I will check the spark on the plugs today.

There is no engine alarm when the shaking and power loss occurs, so this may be a sign that overheating doesn't occur? Is there any way to disconnect or turn off the SLOW-system?

 

[Chris1956]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

Disconnecting the temp sensors will deactivate the SLOW system, if they are the cause of it. If it is a bad powerpack or something else, this will not fix it. Testing the temp sensors is real easy. If they are grounded, and the engine is not overheating, they are bad.

 

[bob johnson]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

you ahve to do a basic set of checks to establish a ground line before you move onto some of the complicated tests

check compression in all cylinders
check spark with a spark tester( not with spark plugs)
then check the spark plugs( yes plugs can go bad)

once you establish that uou have even and good compression and that you have a hot quality spark being sent to the plugs... you can move onto other tests.

I would run the motor and verify with your hand or better yet an infared thermometer ( they are really cheap these days).

the slow system engages when a temp sensor detects a temperature over 220 degrees and it starts to shut down spark in some of the cylinders so your motor CANT run past 2500 rpm....if this happens ...TWO things have to happen to DEACTIVATE the SLOW system

ONE, the temps have to come down below about 200 degrees( i forget the exact temp)
TWO the ignition key has to be turned off.

when you have done those checks, then come back and give us the results


bob

 

[Haffiman]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

To be sure the SLOW does not get activated by any switch on engine, you must disconnect the brown leads going into the power pack. Disconnect temp switches will not eliminate error in other switches or harness.

 

[JohnMartin]

Re: Extreme vibrations from 1997 Johnson Ocean Runner V4 115hp Two Stroke

Thanks for all the answers! I did some work on the boat yesterday, and have now established some facts:
- There seems to be no problem with the fuel system, including piping and fuel pump
- Disconnecting the temp. sensors made no difference, and the problem did not seem to be temperature dependent
- The problem starts at 2800 rpm every time I try to give the engine throttle

After consulting two quite experienced mechanics I have concluded that the problem is most lightly related to a rpm-sensor on the flywheel or some kind of optical ignition system. I will therefore take the boat to a local boat workshop to do some electric checks, and change the broken parts.

Again, thank you so much for all the help here on iboat!