1999 johnson 90 hp fuel problem???????

[TEXAS ROD WORKS]

I have a johnson 90 ,1999 mod, prob is that when you run it up to 4500 rpm's it will run great for bout 300yds then it will start to act fuel starved, if i pump the bulb it will run fine. I have put 2 diff vro pumps on , changed the vapor sep. commpression on all 4 within 10psi. what next? none of this has fixed the issue. carbs were just serviced ran on portable tank , checked tank on boat i'm lost now!!!!!!

 

[Faztbullet]

Re: 1999 johnson 90 hp fuel problem???????

Does it starve on the portable tank??? Did you check/change the pulse limiter? Replace the fuel line from the filter cover to the plastic inlets and see if you have air appear in line,if so check/replace the plastic inlet for the fuel/oil as I have seen these cracked and they will suck air but wont leak under pressure.... the inlet is part #61,pulse fitting is #5 and the hose is #81.

 

[GatorMike]

Re: 1999 johnson 90 hp fuel problem???????

I was going to suggest the same thing. My boat was doing the exact same thing and I tried everything I could think of. Finally I borrowed the 6 gallon portable tank from my sons jonboat and hooked it up. She ran great. Once I had isolated the problem I started searching for the exact cause and found an inline fuel/water separator the previous owner had installed in the bilge compartment that had never had the filter changed.

Funny thing is a week later some guy at the boat ramp was complaining about the same problem and I still had the portable tank in my boat so I put it in his boat and we went for a ride. He said his boat had not ran that good in months making me look like some kind of a mechanical genus.

 

[TEXAS ROD WORKS]

Re: 1999 johnson 90 hp fuel problem???????

it still does the same thing on a portable tank. tried diff hoes and tanks still the same , i have run out of things to check!!!!!

 

[Silvertip]

Re: 1999 johnson 90 hp fuel problem???????

If squeezing the primer bulb helps, then the issue is related to your VRO installation. Were these new pumps or used? Verify the installation and routing of all hoses. You get a short distance at WOT because that's about how long it takes to empty the float bowls. They float bowls go empty because the pump is not filling them. If the floats are set wrong, they may be shutting off to quick and bowls can't be filled properly. Were the carbs worked on recently?

 

[TEXAS ROD WORKS]

Re: 1999 johnson 90 hp fuel problem???????

the vro pumps were factory new pumps , the carbs have been serviced recently all of the work has been done by the most reliable omc dealer / repair shop in this area. the hose routing is correct for the pre-mix vro pump (no oil res.) all gas is pre mixed in the tank.

 

[Faztbullet]

Re: 1999 johnson 90 hp fuel problem???????

Does it drop back to about 2000rpm??

 

[TEXAS ROD WORKS]

Re: 1999 johnson 90 hp fuel problem???????

no, if i leave it at wot it will die. I talked to the original owner of the motor , he said that he has always had the problem with it. he place a 5 psi pump between the tank and the water sep. at wot when it starts to die if you turn that pump on it will run all day. I thought for sure it was fuel pump related but the vro has been replaced with two diff. pumps both brand new and the problem is still there.

 

[kenmyfam]

Re: 1999 johnson 90 hp fuel problem???????

no, if i leave it at wot it will die. I talked to the original owner of the motor , he said that he has always had the problem with it. he place a 5 psi pump between the tank and the water sep. at wot when it starts to die if you turn that pump on it will run all day. I thought for sure it was fuel pump related but the vro has been replaced with two diff. pumps both brand new and the problem is still there.

Check the pump output.
Muffs on
Disconnect plug wires
Unhook the pump to carb's line
Crank into a container.
Continuous strong spurts = O.K.
Start strong and tapers off = starting to fail
Dribbles out or stops pumping = failed
This is assuming your tank is properly vented.

 

[TEXAS ROD WORKS]

Re: 1999 johnson 90 hp fuel problem???????

Just got the boat back from the shop , still not fixed I don't know what to look at next . mech found two o-rings that were in the vapor seperator he thought were bad so he changed them out 160$$ later still not fixed . he is the best omc tech in the area and he could not figure it out . guess I'm shoppin for a new motor..........

 

[kenmyfam]

Re: 1999 johnson 90 hp fuel problem???????

Just got the boat back from the shop , still not fixed I don't know what to look at next . mech found two o-rings that were in the vapor seperator he thought were bad so he changed them out 160$$ later still not fixed . he is the best omc tech in the area and he could not figure it out . guess I'm shoppin for a new motor..........

I would be shopping for a new mechanic and not a motor !!!
Have all the above suggestions been tried out ???

 

[TEXAS ROD WORKS]

Re: 1999 johnson 90 hp fuel problem???????

I have tried everything , with season getting close I have got to get something fixed or get a new one . I don't get it if i force fuel to it it will run all day long . fuel pump is good carbs are right ,can't find any air leaks anywhere? commpression is good , all new gaskets on the carbs.

 

[arnettjs]

Re: 1999 johnson 90 hp fuel problem???????

I had a similar problem last year on my 1992 Johnson 115. After much frustration, it turned out to be an improperly seated carburetor gasket (post rebuild). Apparently, after a few minutes of running WOT, the gasket would soak up fuel and expand enough to cause the outboard to die. Once that was fixed, the problem never materialized again. Hope that helps.

 

[bob johnson]

Re: 1999 johnson 90 hp fuel problem???????

I would be shopping for a new mechanic and not a motor !!!
Have all the above suggestions been tried out ???

i need a parts motor!!

sell me that junk and buy yourself a trouble free summer!!!


did you read faztbullets first reply???? and tried looking at his suggestions?

bob

 

[gleninaz]

Re: 1999 johnson 90 hp fuel problem???????

We just had the same problem on my old 1990 115 eveinrude. We replaced the VRO with a new one and still had the problem. It turned out to be the anti-siphon valve at the tank. We knoked out the ball and it ran great. We are buying a new anti-siphon valve tomorrow for $11. That was a costly experiment.