1989 200hp Johnson looses power - Diffrent

[Grady19]

My 1989 200hp will start fine and run at 4800rpm at WOT for about 15 minutes. It then looses power to about 3000rpm. If I throttle back to a stop and then try to take off it doesn?t have much power and takes a long time to plane. If I throttle back and turn the motor off and them back on most times full power is restored and I can plane easily and get back up to 4800 RPM.

I have read many posts but have not seen this specifically. Things I have thought about trying include disconnecting the Oil sensor and Replacing the Power Pack. I have checked to make sure the magnets in the fly wheel are in good shape and properly glued. I have had that problem before.

What could be wrong?

Also, should I have more top end RPMs on a 19 foot boat?

Any ideas or troubleshooting tips are very much appreciated.

Thank you,

 

[elhombre]

Re: 1989 200hp Johnson looses power - Diffrent

Some experts will weigh in here I'm sure, but what caught my eye was 4800 rpm @ wot. You mentioned it running like this for 15min or so. Sounds like it's overpropped. My rule of thumb is if it won't turn up rated rpm at wot, pull it back some so you don't damage the powerhead with "preignition". Don't quote me but I suspect rated rpm on that motor is around 5500 rpm. When was the last time your carbs where rebuilt? You might search "linc n sinc" to make sure your ignition timeing is correct - good luck with this

 

[Grady19]

Re: 1989 200hp Johnson looses power - Diffrent

Thanks for response - It used to easily hit about 5200 to 5300 rpm. I have another prop I can put on with less pitch to try. I rebuilt the carbs about 4 years ago. The problem seems electrical to me because of the way it kind of resets when I turn the ignition off and on. I am up for doing the carbs again though. It may be fuel starvation although I have already replaced the fuel line, bulb, inline filter, and check valve.

Any additional responses are much appreciated.

Grady19

 

[kenmyfam]

Re: 1989 200hp Johnson looses power - Diffrent

How about the fuel pump ??? Could be starting to fail on you. Have you tried squeezing the primer bulb when it does this ???

 

[jonesg]

Re: 1989 200hp Johnson looses power - Diffrent

Sounds like it lost a step or two, I'd baseline it.
Compression test
spark gap test

If they pass muster.

rebuild the carbs.
Get the right prop on it and retest.

 

[Grady19]

Re: 1989 200hp Johnson looses power - Diffrent

David

Thanks guys. Still have this problem but it is getting better. I have been running a fuel conditioner with a carb cleaner it through the system. It seems to be helping. I can get 5500rpm know but occasionally still get the sudden power loss. When I stop and turn off the engine the engine and turn it back on I have full power again. Just weird thing. Not sure what to replace next or if I should. I suspect the power pack is failing periodically or going into half speed mode for an unknown reason.

Best,

Grady