Johnson J4BRECJ leaning out....

[MahtyMaht]

Twin 2 stroke 4 hp, looks like a '98. It starts easy, moves good water thru it, raps up good, but if I run it from 1/3rd throttle or lower in the can, it will start to lose RPM, and if I twist the throttle, it bogs and dies. When it starts the downward RPM drift, if I pulse the choke right quick, the RPMs come right back up. It has done this with two different tanks and fuel lines, so I'm thinkin' engine related fuel delivery problem. I don't have a manual, it belongs to a friend, and I don't want to start taking the whole durned fuel system down, if somebody here can get me pointed at the best place to look for problems.

 

[hidef]

Re: Johnson J4BRECJ leaning out....

How does it run on the internal tank? If it runs on that with no issues then most likely the fuel pump needs to be rebuilt.

 

[MahtyMaht]

Re: Johnson J4BRECJ leaning out....

You know, I saw a fuel line fitting, so I plugged a line on it, and lit it off - sniff-checked the fuel in the on-board tank, but I didn't run the engine from it. I'll do that next. The fuel in there smells new. i pulled the plugs, just for grins, and they had wet black carbon on 'em, but they were easy to clean. Before I cleaned them, I sniffed 'em, and they stunk of varnish. Ima fire tha sucker up from th on-board, and I'll be checkin' back. Thanx, Hidef.

 

[MahtyMaht]

Re: Johnson J4BRECJ leaning out....

New info_I just went out and lit it off with the onboard tank, and now that it's dark, I'm using a light, and I saw what appears to be a fuel leak. i don't know exactly where it is, but I can see fuel on the float boat rim gasket. I took the 2 bolts out from under the forward cowl half, and the 2 bolts that tie the front to the rear cowl, but, of course, the front cowl half won't come off - wtf am I missing? I need to be able to see the front of this thing.

 

[MahtyMaht]

Re: Johnson J4BRECJ leaning out....

Does this engine get fuel from the external tank when the choke knob is in the fuel shut off position?

 

[hidef]

Re: Johnson J4BRECJ leaning out....

I think it does if it is hooked up.

 

[MahtyMaht]

Re: Johnson J4BRECJ leaning out....

What I thought was a fuel leak is actually just the really reflective surfaces of the plastic carburetor. Never saw a plastic one before. Snatched the cover off the fuel pump, and sniffed it - smells like two year old fuel. I suspect that there's somethin' funky inside the carb, but of course, no one in our nation seems to know how to get the choke knob off, so I can't get the cowl off.

 

[hidef]

Re: Johnson J4BRECJ leaning out....

Should just pull off if it is part 42

http://www.marineengine.com/parts/j...RECRJ&manufacturer=Johnson&section=Carburetor

 

[MahtyMaht]

Re: Johnson J4BRECJ leaning out....

It is # 42, and that pic is how I know it's a separate part. The carb end of that knob has splits in the sleeve where it plugs onto the shaft that actuates the choke and valve, but I am scared to pull it hard for fear of breakin' the durned thang. I got the feelin' that since it's supposed to be pulled to choke it, there has to be some way it's locked on, so it doesn't just come off in the operator's hand out on the lake.

 

[hidef]

Re: Johnson J4BRECJ leaning out....

It might be time to buy a service manual.

 

[MahtyMaht]

Re: Johnson J4BRECJ leaning out....

If it was mine, or for money, I'd already have it, Hidef - As neither of those conditions pertains, it's gonna be a 3 day joyride with a tank full of seafoam, and a fat ice chest. Maybe I can wear the problem down.

 

[MahtyMaht]

Re: Johnson J4BRECJ leaning out....

Update - I put a pint of straight seafoam with a taste of 2 stroke oil in the on board tank, hooked up the remote tank, and ran it in the can for a couple of hours. Now and again, I'd switch to the on board tank to dose it hard with seafoam. After a couple of hours of this, it got to the point where it would no longer run out of gas and die unless it was idling. Then I ran it with the on board tank till the float bowl was full, killed it, and left it over night. Next day, I filled the on board with a sane mix of Seafoam and ran it up and down the creek. Now it only gets fuel starved at dead idle in gear. I think the cure all in a can is actually going to work.