2000 Johnson 4hp won't stay running at low speed

[sefuller]

I have a newly acquired 4hp Johnson that we use on an inflatable to get out to our mooring. We have only had it out a few times, and mostly within the no wake zone in our harbor. It ran well the first couple of times out, then one time I somehow hooked the gas line up backwards, and put a couple of squeezes on the bulb. I realized right away because the bulb was so hard. I don't know if it was just coincidence or not, but now it seems that after running for a minute or two at very low rpms, the motor dies and has to be choked to be restarted. Last night we took it out on the open water and ran at WOT or close to it for almost an hour without a single hiccup, but back in the harbor, it will still only run a minute or two at idle speed. Since I store it on a rack under the dinghy, I usually unhook the gas line a minute or two before we dock to run the gas out of the carb so it does not drip out while it is on the rack. I do have fresh gas in it, and it is always kicking out a good stream of water while it is running. Where do I get a service manual for this year motor - the one in the site link only goes through 99? I don't have an owner's manual either - what is the red plastic adjustment screw for?<br /><br />Thanks much -

 

[OBJ]

Re: 2000 Johnson 4hp won't stay running at low speed

You should be able to order both manuals from any John/Rude dealer Scott. <br /><br />Give this a try for the idle problem Scott....<br /><br />When it starts to die out at low idle, squeeze the primer bulb and see if it picks back up. If it does, likely the fuel pump is getting weak and needs a rebuild/replacement.<br /><br />If the engine does not pick back up and pulling the choke makes it run more, the carb probably needs a cleaning and rebuild. <br /><br />Keep us posted...thanks.

 

[sefuller]

Re: 2000 Johnson 4hp won't stay running at low speed

Originally posted by OBJ:<br /> When it starts to die out at low idle, squeeze the primer bulb and see if it picks back up. If it does, likely the fuel pump is getting weak and needs a rebuild/replacement.<br /><br />If the engine does not pick back up and pulling the choke makes it run more, the carb probably needs a cleaning and rebuild. <br /><br />Keep us posted...thanks.

It does not seem like hitting the primer or choke while it is dying helps, but because it only happens from idle, it dies so fast that it's hard to tell. I thought the weak fuel pump would exhibit itself more at high throttle than low? After it dies, it usually won't start without the choke on for one pull of the starter, then it will fire up and run again.<br /><br />Thanks,<br />Scott

 

[OBJ]

Re: 2000 Johnson 4hp won't stay running at low speed

Scott I would consider pulling the carb and cleaning it out throughly. Very possible you got some junk floating around there fowling the idle passages. Since you just acquired the engine, you probably don't know how long it set before you aquired it or what type of maint record it has. It would also be a good idea to put gas stabilizer in the engines fuel tank if you are not doing so already.