No power at hole shot

[iwannabfishn]

My 1993 Johnson 120hp started having problems yesterday. It starts up fine and if I put it in neutral and rev the engine, that sounds fine. When I put it at full throttle to go it has no power. It will just barely get up on plane. Once on plane it doesn't seem to hit top speed either. I just drained all the gas and put fresh in a couple of weeks ago. I am looking for direction on what to check. Could it be the throttle cable?

This might be unrelated, but I often have to pull back on the throttle lever to get the boat to start. I guess the neutral safety switch is going bad? I thought I would throw that in, but that has been happening for a while.

Model number is VJ120TLATS

[JohnG28]

Possibly carb related? May need a carb rebuild if it hasn't had one recently, sort of sounds like it's not getting fuel at full throttle. Just a guess but if it runs well at other speeds I'd think something fuel related would be first place to check. What made you empty and replace the fuel a few weeks ago?

[Solarman]

The neutral safety switch is supposed to make you pull throttle back to start? If not in neutral, one switch prevents motor from cranking, and one neutral shift switch on the motor (if yours has it) should limit RPMs to 3k, to prevent over revving in neutral.

If loss of power when throttling in forward, it could be; compression related-test; spark related (bad plugs, spark interruption/limiting- neutral position switch, heat or oil sensor, or spark advance not working when throttle moves; or, fuel problems - bad fuel, blocked filters -weak pump, restriction or leaks in lines, trash in jets/ needle valves, carb pas-sages, and possibly to much fuel - usually leaks out front of carbs - float settings or trash.

Yes, there are other things that can affect running, but these are the basics that cause this scenario.

To know more about your problem, more info on your motor, what you have done, or what happened when it stopped running good? Did you try pumping the bulb, did that do anything?

Good luck. Post back if you have more info.

[iwannabfishn]

I pulled the gas out because I didn't have stay bil in it and it sat for about 6 months without use. I just used that gas in the lawn mower. I also changed the spark plugs. I was thinking it might be the throttle cable because the engine doesn't seem to go much until about 3/4 throttle. I guess that could be carb related though. The carbs haven't been rebuilt ever or at least not in the past 15 years.

[Solarman]

If you have the Cowling off, watch the throttle and shift linkage (motor not running) while you move the control lever from neutral to forward and through to full throttle, and back to neutral, also into reverse (linkages should move when you move the control lever). If linkages at motor do not move when throttle lever moves, then inspect cables for problems. If shift and throttle linkages move when you move the control lever, then cables may be ok.

Also, if the motor sat up for past 6 months, it probably needs carbs cleaned properly. It needs to be done by someone that knows how to clean carbs properly.

Post back what you find out, our what you plan to do.

[iwannabfishn]

So, it was the carbs. I took the air handler off and check the throttle positions and that seemed OK looking down the carb, anyway. I started it up and ran a can of sea foam through it. I then took it to the lake and ran it. It completely cleared up after running it wide open for about 30 seconds. Something cleared out and it ran great after that the whole time we were there. Thanks so much. I guess it probably high time for a carb rebuild though. Thanks again!