Intermittent power loss in Johnson GT150

[bigbeariron]

Hi everyone, I am new here. I am posting because this problem has been plaguing me for about a year now.

Background:

I have a 1988 Johnson GT150 Model No. J150STLCCA
I bought this motor about 2 years ago, just before I bought it the power packs had been replaced.
The VRO is disconnected and I mix my fuel 50:1

The Problem:

Initially it started at cruising speed, about 4500 rpm+. I would be going along and loose some power. I had to open it up to full throttle and it would still not climb above about 5000rpm. (Not exactly sure if the RPM gauge is correct)
I am not losing all power, it just keeps me at about 55mph instead of 75mph where it used to run.

This problem consistently got worse. Now I have a hard time getting out of the hole, and full speed is only about 55. Every once in a while it will "kick in" and the boat immediately speeds up. Then it will slow down, then speed up, intermittently.

I also noticed that when I do happen to get full power, if I adjust the trim, I temporarily lose power.?!?

Also, when I change the spark plugs they are wet and oily.

What I have done:

I Have checked all of the electrical system to the best of my ability.
I have cleaned the carbs and jets.
I have replaced the fuel filter and primer bulb.
I have changed plugs and wires.
I have checked compression on all cylinders, they are all good (the same).

Can anyone give me any suggestions? I have been fighting with this for a while now and I need to get it fixed.

Thanks, Keith

 

[clanton]

Re: Intermittent power loss in Johnson GT150

The stator is bad( if i adjust the trim I temporarily lose power). May have other ignition and charging problems. Do a complete check of ignition system with peakreading meter, saves replacing good parts.

 

[bigbeariron]

Re: Intermittent power loss in Johnson GT150

I haven't had any problems charging the battery. I haven't had to charge my starting battery since I have owned the boat. Do you still think it is the stator?

I just did a resistance test on the stator (hooked an ohmeter between terminals A&B) and came up with 897 ohms. My Clymer manual says to replace if it is 970 +or - 15 ohms.

 

[clanton]

Re: Intermittent power loss in Johnson GT150

Yes, but still need to check with meter. There is service bulletin for this system that states run engine full throttle in water ,trim up, if engine loses power or misfires stator is bad

 

[jonesg]

Re: Intermittent power loss in Johnson GT150

At least the good news is you didn't waste another yr chasing phantom fixes.