Kicker stalling at low RPMs after 20 minutes

[flatfishfool]

I have a 2010 9.9 tohatsu kicker that is having a problem. It starts and runs flawlessly but only for about 20 minutes at low trolling speeds. After that it will start to sputter and stall and die. It definitely doesn't sound like too low of RPMs or an "idle problem" but much more like a fuel problem. But I don't understand why. When it stalls I can prime it a little and get it going again but it will then die about every 3-5 minutes.

It is linked to one of the outlets on my Racor filter on a 3 foot OEM hose. After pondering awhile I thought that maybe it is consuming so little fuel it can't overcome the 3ft hose and 1.5-2ft elevation change from the tanks. So I tried occasionally squezing the primer ball to keep more pressure up. That seemed to help but it doesn't stop the problem. I like to troll at bare minimum speed/RPMs so I tried ticking it up a little but it still stalls. I tried moving the hose around to different positions and again no real help. I tried occasionally revving it up but no difference.

What am I missing?

[Will-C]

I'm guessing it has something to do with your fuel cap's venting system. It's like dipping the straw into a glass of milk and holding your finger on top. Remove the fuel cap and reinstall if that allows it to run again you have found the problem and then you can figure out why the fuel vent is not venting. Our dink motor has a closable vent so fuel can not leak when it is stored on it's side. If it has one of those give it a twist.
D.D

[rogerbum]

Sounds to me like there may be a vacuum being created that is preventing/limiting fuel flow. If that's the case, if instead of running at low idle you ran at high RPM's it should stall more quickly. Have you tried that? If you do and it runs fine at speeds above idle, then it's unlikely to be a fuel flow issue.

If at higher speeds it still sputters and dies out and does so more quickly then fuel flow really is the problem. Since I assume that the racor to which the kicker is connected, also feeds the main engine and since you haven't mention similar problems there, the feed to the racor and the fuel system venting is all OK.

That leaves the path from the racor to the carb in the kicker as the likely suspects for fuel problems. It could be that there's some schmutz inside the racor that is blocking or partially blocking the outlet, maybe teflon tape from the connector. Also could be problems with the hose between the kicker or a fuel filter within the kicker. Does the priming bulb maintain it's shape or does it get sucked flat? If the latter, there's blockage prior to the bulb. Have you looked at/changed the fuel filter in the engine itself? There should be one in line inside the engine cover.

[starcrafttom]

you have a bad primer bulb. replace it. some where the buld is getting air and you are losing your prime. commom problem. just change it out and maybe the whole hose. It is not happening at high throttle is it? thats because the fuel pump is pulling enough pressure to keep the buld full.

[Sam Walker]

Hey Flat. I have been having the same problem w/ my 6 hp Nissan (Same maker, different brand). It runs great for 20-30 minutes then requires a primer bulb squeeze (Where is the Johnson girl when I need her) every couple of minutes to keep it running. I am using a 3 gallon portable tank. The problem is reduced but not eliminated when I raise the level of the fuel tank when compared to the motor to reduce the head (vacuum pressure) loss. My problem has been at all speeds.

Tom thinks that it is the primer bulb and hose. That is where I started also. However, since then, I have replaced every single piece in the line from the tank itself, to the hose and primer, to both sides of the quick connect, to the fuel hoses, filter, and pump on the motor . Nothing has changed the situation.  

I have run the motor in the tank at home w/ the cowling off and can see the fuel run out of the fuel filter and being replaced by air. I suspect that I have an air leak that the replacement of every part in the line did not cure. My next stop is to use Rescue 911 tape and fully wrap the quick connect. I am pretty sure that is where my problem is.

I hope that you get it figured out. Please let us know when you do. It might help me zero in on at least this one of my problems.

[Chester]

The hose clamps could be the problem. Radiator worm drive style clamps can pinch the hose and introduce leaks.
See Larry H's posts in this thread, Linkey

[Sam Walker]

Hi Chester. I saw Larry's post earlier in the week and noted that I should change my clamps. That is on my list also. I am currently using the worm style clamps.

Thanks.

[flatfishfool]

Thanks for all the new ideas. I will look into some of these. I am now focused on the primer bulb and the vent cap on the tank and possibly the filter or Racor body/connections.

Some of these replies reminded me that last time I was out I did indeed have a few barely noticeable hesitations on my main as well. They were very minor so I forgot about them until the diagnostic dialog pushed me further up the fuel system.

The two motors share the same Racor and so the same main line to the tanks and same tank. I have two tanks with a valve to switch between them but both are of the same vintage so if the vent seal is not opening on one it's not unreasonable to think it's happening on both. And, while the line and bulb to the kicker is virtually new, the main lines from the tank to the Racor and the bulbs on them are getting old and stiff. I have suspected the vents before and have wiggled them and opened them wide when running but I should take them apart and put back together or just get some new caps.

Lots of new ideas to try. Thanks. I will probably do several changes at once so may not determine the exact cause but I will post my post (hopefully) problem analysis.