25HP Johnson 2 Stroke Missing, Sneazing, Won't Run Worth $&#*@

[ronnieb09]

Motor is a 2003 Johnson 25HP 2 Stroke, manual start with tiller steering.

I go to start up the motor for the first time this season, and its running rough...have to idle it up to keep it running, no power under load. I properly winterized it as I do every year, been a nice reliable little motor in the past. Tried two different tanks of fuel, verifying oil mixture is right. I went ahead and rebuilt the carb, new valve and gaskets - cleaned every orifice, etc. I adjusted fuel mixture screw, but no improvement on running. Also changed fuel line and bulb from tank to engine. No change.

Checked compression, both cylinders look good and even. Checked spark with tester, both coil packs check good. Both spark plugs look the same condition, oil/fuel fouled - almost like it's rich? Engine fires right up, just won't run worth anything. Taking a shot in the dark here guys, any suggestions?

Thanks!!!

Ronnie

 

[2manband]

Re: 25HP Johnson 2 Stroke Missing, Sneazing, Won't Run Worth $&#*@

Motor is a 2003 Johnson 25HP 2 Stroke, manual start with tiller steering.

I go to start up the motor for the first time this season, and its running rough...have to idle it up to keep it running, no power under load. I properly winterized it as I do every year, been a nice reliable little motor in the past. Tried two different tanks of fuel, verifying oil mixture is right. I went ahead and rebuilt the carb, new valve and gaskets - cleaned every orifice, etc. I adjusted fuel mixture screw, but no improvement on running. Also changed fuel line and bulb from tank to engine. No change.

Checked compression, both cylinders look good and even. Checked spark with tester, both coil packs check good. Both spark plugs look the same condition, oil/fuel fouled - almost like it's rich? Engine fires right up, just won't run worth anything. Taking a shot in the dark here guys, any suggestions?

Thanks!!!

Ronnie

Does yours have an adjustable high-speed jet (behind the float bowl drain plug)

Did you rebuild and/or adjust that portion? Many people don't because it's tough to access without a special tool (either bought or made)

 

[ronnieb09]

Re: 25HP Johnson 2 Stroke Missing, Sneazing, Won't Run Worth $&#*@

Does yours have an adjustable high-speed jet (behind the float bowl drain plug)

Did you rebuild and/or adjust that portion? Many people don't because it's tough to access without a special tool (either bought or made)

Mine is not adjustable, just a screw in jet. I did remove and clean it though. I followed the Johnson manual to the T, the one adjustment they discuss is the mixture screw. I can lean and rich out the mixture, but it runs rough the entire time regardless of mixture screw position.

One thing I did notice is that when I push in the primer pump while its running, it does seem to idle up and run smoother.

 

[2manband]

Re: 25HP Johnson 2 Stroke Missing, Sneazing, Won't Run Worth $&#*@

One thing I did notice is that when I push in the primer pump while its running, it does seem to idle up and run smoother.

That sounds like either a leak in the primer bulb/fuel hose assembly (but probably not since yours are new)

or the fuel pump. That would be my prime suspect based on what you describe.

 

[ronnieb09]

Re: 25HP Johnson 2 Stroke Missing, Sneazing, Won't Run Worth $&#*@

Let me see if I can get a fuel pressure gauge on this thing, verify that I am losing pressure.

 

[ronnieb09]

Re: 25HP Johnson 2 Stroke Missing, Sneazing, Won't Run Worth $&#*@

Put a fuel pressure gauge on today and test ran the motor, pump is putting out plenty of pressure at 2-3 psi depending on rpm. I did some more investigating and watched it run, and I swear this thing seems like its running rich. Wants to bog down when you give it try to increase throttle, and it's smoking pretty bad. I'm not up to speed on how to check/adjust timing on these things, any suggestions?

Thanks!

Ronnie

 

[ampcarfan]

Re: 25HP Johnson 2 Stroke Missing, Sneazing, Won't Run Worth $&#*@

Maybe the primer is leaking causing it to run rich (Bad O-rings in the plunger) ?? Maybe try gently pinching the primer hose where it goes into the carb (top right near the manifold when facing the carb), then run it enough to see if you can get it to clear out the excessive fuel.