Stalls after idling for too long

[imjus4u2nv]

Was out this morning (finally got into some schoolie bass) and an issue that has been around for a while reminded me it was there.
I end up running at low speeds/1400 rpms (no wake) for about 10 minutes boat runs fine (same at WOT and everywhere in between). I will fish then start up and move a minute or two away and repeat. After doing this the boat doesnt want to idle long and usually stalls out after a 30 seconds to a minute or so. It sometimes sneezes/coughs then stalls. Every once in a while I will have to prime the bulb again to start it backup.
Thinking maybe a bad check valve in the float for having to reprime? Also anyone have a check valve in-line of the gas hose?
Or maybe the fuel pumps - was going to replace lower fuel pump (have two new pumps in the garage, should I just do both? Hate to mess with more then needed).
Boat is also revving up a little like usual on startup but seems to take a while to get the rpms to settle down (when cold and warm - can turn off after run ning and restart and same thing), so when start have to wait about 30 seconds or so for rpms to drop to 700 where I can safely shift into gear.

 

[seasick]

Could be the pumps. If you have new ones and the old ones are several or more years old, it can't hurt. The pumps are plumbed in series so you should change both.

That said, I find that weak low pressure pumps are more of an issue when cold.
Often a stall can be caused by fouled plugs which can happen with long periods of trolling if the mixture is too rich. If you want to test out that theory, after trolling, run the motor for a minute or so under load and at speed and then see how it idles.

 

[wspitler]

I'd pull the plugs and my guess you'll find them running rich. Don't know which engine type and size, but always a good and easy place to start. My F150 did the same and I swapped the throttle position sensor and re-synched the butterfliy. It was running rich at low speeds and eventually loaded up. My F150 was fine after high RPM runs, but after an hour of trolling would do like yours.

 

[imjus4u2nv]

Will work on this week, will pull plugs and swap out since I have a new set and will do both pumps and will report back.

 

[SkunkBoat]

So many possibilities, some already mentioned, but ....VST filter, fuel injectors, LP pump..

Sneezes? is it an OX66? mine stopped sneezing out at idle after new VST filter, Pressure Regulator screen and fuel injector cleaning.

 

[Sparkdog118]

sometimes a primer ball can cause some issues. It is easy to replace. Make sure the arrow for the primer ball is pointing to the sky at all times. Sometimes this helps.

 

[seasick]

If it is a 2 stroke, in addition

So many possibilities, some already mentioned, but ....VST filter, fuel injectors, LP pump..

Sneezes? is it an OX66? mine stopped sneezing out at idle after new VST filter, Pressure Regulator screen and fuel injector cleaning.

to possible over rich gas mixture, the plugs could also be oil fouled due to excessive oil injection amounts at trolling speeds

 

[seasick]

So many possibilities, some already mentioned, but ....VST filter, fuel injectors, LP pump..

Sneezes? is it an OX66? mine stopped sneezing out at idle after new VST filter, Pressure Regulator screen and fuel injector cleaning.

Based on that, I have no idea if the issue was, VST, pressure regulator screen or fuel injectors? The first two can have similar symptoms but different from the last one, injectors, which could cause too lean or too rich a mixture.
The first two would also probably show up with a fuel rail pressure test.
I wonder; did you look at the old parts to see if for example the screens were clogged?
Just busting your chops a bit

 

[Sparkdog118]

If you are sneezing, it is a true sign of lean fuel.

 

[SkunkBoat]

Based on that, I have no idea if the issue was, VST, pressure regulator screen or fuel injectors? The first two can have similar symptoms but different from the last one, injectors, which could cause too lean or too rich a mixture.
The first two would also probably show up with a fuel rail pressure test.
I wonder; did you look at the old parts to see if for example the screens were clogged?
Just busting your chops a bit

It was all three things clogged up.

 

[seasick]

Now that makes sense.

 

[seasick]

If you are sneezing, it is a true sign of lean fuel.

The SX series motor will sneeze and often stall if the idle is too low. I can't say if the mixture is lean in that case.

 

[imjus4u2nv]

Should have mentions this is a two stroke, willl work on this weekend, thanks all.

 

[seasick]

Take a look at the 'precision oil injection' linkage, the link from the oil pump to the throttle. Make sure is is not broken or disconnected and check that when the throttle is closed, the oil pump linage just barely hits the stop. If there is space when the throttle is closed, the pump will over oil the mixture.
Note that bad or clogged O2 sensor( and/or thimble) will cause a rich mixture which will can foul the plugs. A rich mixture is not so much an issue at higher speeds and loads since the motor needs more gas in that case.

Have you noticed when it stalls and you restart it if there is more exhaust smoke than usual? If so, is the smoke blackish or blueish and then changes to light whitish smoke. It can be hard to really tell since most of the exhaust is released under water.

 

[imjus4u2nv]

Take a look at the 'precision oil injection' linkage, the link from the oil pump to the throttle. Make sure is is not broken or disconnected and check that when the throttle is closed, the oil pump linage just barely hits the stop. If there is space when the throttle is closed, the pump will over oil the mixture.
Note that bad or clogged O2 sensor( and/or thimble) will cause a rich mixture which will can foul the plugs. A rich mixture is not so much an issue at higher speeds and loads since the motor needs more gas in that case.

Have you noticed when it stalls and you restart it if there is more exhaust smoke than usual? If so, is the smoke blackish or blueish and then changes to light whitish smoke. It can be hard to really tell since most of the exhaust is released under water.

It does smoke a bit after restart (hard to tell if if bc cold or oil but seeks to get betterwhen it warms up) butdef throw a cloud (seems to dissipate quickly butfirst start of the day ahead throws a small cloud down the street). Had checked last season (smoke is not new) and oil linkage seemed fine and was afraid to mess with. Plan to work in today/tomorrow.
Appreciate all the responses!