1993 Johnson 120 HP surges at high rpms

L

lightingbolt52

Recruit
Joined
Jul 16, 2005
Messages
2
I have a 1993 120 hp johnson outboard with only about 278 hrs on it. The vro has been removed by a mechanic when I first test rode it everything seen to be ok. I went out yesterday and ran fine at low rpms then at about 3000 or so it starts to surge. The bulb seems to pump up hard and stay. I took the line off at the carb. and pumped the bulb and it seem to have plenty gas flow. Any sugestions?
 
W

Walker

Captain
Joined
Jun 15, 2002
Messages
3,085
Re: 1993 Johnson 120 HP surges at high rpms

Did you replace the VRO with a standard fuel pump or is the VRO still acting as the fuel pump?
 
L

lightingbolt52

Recruit
Joined
Jul 16, 2005
Messages
2
Re: 1993 Johnson 120 HP surges at high rpms

The vro is still acting as the main fuel pump. The mechanic disconnected the vro part of the fuel pump and said to mix the oil 50 to one.
 
B

Blueclaw

Petty Officer 3rd Class
Joined
Jul 6, 2005
Messages
81
Re: 1993 Johnson 120 HP surges at high rpms

surging at high speed usually come for a fuel delivery problem or bad fuel.<br /><br />check gas tank vent for restriction.<br /><br />fuel line restriction, dirty fuel filter.<br /><br />fuel system air leak:<br />take a clear piece of tubing inline to the input of the fuel pump and watch for air bubbles. you should only see a bubble now and then.<br /><br />fuel pump diaphram leaking.<br /><br />carb float sticking closed or not adjusted properly.<br /><br />high speed jet clogged or restricted.
 
C

CJY

Lieutenant Junior Grade
Joined
Jun 19, 2005
Messages
1,242
Re: 1993 Johnson 120 HP surges at high rpms

As Blueclaw has stated, fuel system air leak. Mine was doing the exact same thing. I pulled off the hood(motor not running) and watched the lines where they attached to the carbs as I pumped the bulb. Sure enough, gas oozed out at that point. So , under running conditons the motor was sucking air causing the surge. Simple turn of a screwdriver fixed the problem. Check that if you have not already.<br /><br />John
 
You must log in or register to reply here.
Top