Boat stalling out

[Chugger]

Hey Guys,

 

So my boat wants to stall out now and again at very low speed (think laker trolling speed). ANyone have any thoughts on this? I've got a new fuel line, they checked to ensure there was no fule leak anywhere, cleaned the carbs out.

I noticed yesterday when fiddiling with the vent on my gas tank (50 liter)that the tank looked someone caved in, I really loosened off the vent and it stalled out again. Could it be something with the fuel tank? Also, how loose should the vent be?

Thanks for anyhelp you can offer.

 

Cheers,

 

Graeme

[fish_fishburn]

Are you burning old gas from last year?

[Chugger]

New gas at the start of every year.

[Fisherman]

The vent has to be open, air replaces the gas as it is used otherwise you'll have a vacuum in there.

[Chugger]

Yeah I know the vent needs to be open, I'm just not sure how open it should be? It seems to screw in and out, so do I open it all the way? When I did that the engine stalled immediately.

[BillM]

You should be able to open the vent entirely without having the boat stall out. Sounds like you might have a vacuum leak somewhere..

[Chugger]

So what would you do about a vacume leak? Is that something that needs to go to a mechanic or is that something I can figure out on my own with limited engine knowledge? Thanks Bill.

Cheers,

-G.

[ohhenrygsr]

Does the Primer bulb stay fairly stuff?

[DanD]

In my experience fuel starvation at low speeds are not a vent or fuel line issue; it usually is a high speed issue, when the pump is drawing higher volumes of fuel. That being said anything is possible?

As long as there’s even a small amount of air being allowed in the tank; that should be enough at the lower speed; to confirm this leave the fuel cap off or loose when the problem occurs.

This could be a fuel pump issue; that at low rpm it is not drawing the fuel; due to a ruptured diaphragm or the inlet/outlet valve of the pump are leaking internally.

When the motor stalls does it restart right away or do you have to let things sit for a bit?

If it doesn’t start right away; you may have an ignition issue; that when the ambient air under the hood reaches a certain temp; something is shutting down. May also answer why only at low speeds; water pump turning slower and less air flow into the engine compartment? I’m not saying overheating engine but a failing ignition component that doesn’t like the heat.

I take it this is an outboard; if so run it with the hood off and see what happens.

If this is a random, never know when it’s going to happen; you may need to tee in a fuel pressure gage between the pump and carb; to see what the pressure is, during a stall.

And possibly have a spark tester ready to check for ignition after a stall.

There are three types of spark tester that work well; 1- a store bought one that has an adjustable air gap; 2- a good old screwdriver, held 1/8” away from the cylinder head; 3- your fishing partner; “here hold this wire for a second”. This is the best one of the three; if he/she ain’t doing a jig at the back of the boat (after a short crank of the engine) then there ain’t any spark. LOL

Caution pacemakers don’t like the 50K volts that a coil can produce.

 

Dan.

[Chugger]

No the primer ball will lose pressure, I'll find it fairly empty at times.

 

Yeah Dan, the engine is able to start right away after a stall, so I'm not sure ignition is the problem. It for sure only happens at low (trolling) speed, and I've had the fuel pump replaced. It is an outboard (40hp Johnson tiller) I'll pull the cover off and see what happens then.

 

Thanks Guys,

-G.

Edited May 25, 2010 by Chugger

[BillM]

Sounds like air is getting into the fuel system somewhere along the lines... When you open up the vent all the way, the mixture leans out way to much and it stalls the motor out. So now you just need to figure out where that leak is, lol.

 

If you close the vent completely, the motor *should* stall eventually...

[Chugger]

So in theory if there is a leak, I could then close up that vent all together and the motor should just keep running?

[BillM]

So in theory if there is a leak, I could then close up that vent all together and the motor should just keep running?

 

Yup.

[Chugger]

Didn't communism work in theory?

Thanks again Bill.

[BillM]

Didn't communism work in theory?

Thanks again Bill.

 

 

LOL!

 

I hope you get it figured out!

[irishfield]

Sounds like my 5 HP Honda.. the way it came from the factory. It would troll for some time and then cough and die. For some reason I put up with it for awhile and then decided to do something about it. 1/4 turn of the idle jet screw and smoooooth !

 

Find your idle jet.. turn it all the way in and count the turns so you know where it is to start with. Turn it back out to 1 1/4 to 1 1/2 turns and try it again.

Edited May 25, 2010 by irishfield

[Chugger]

Sounds like my 5 HP Honda.. the way it came from the factory. It would troll for some time and then cough and die. For some reason I put up with it for awhile and then decided to do something about it. 1/4 turn of the idle jet screw and smoooooth !

 

Find your idle jet.. turn it all the way in and count the turns so you know where it is to start with. Turn it back out to 1 1/4 to 1 1/2 turns and try it again.

 

What is an idle jet, and do 40hp motors have them?

[irishfield]

If it's carbureted.. it sure does!

 

Not sure if this will attach.. #23 is your screw. I grabbed a generic 40 hp year 1990 to find a diagram at www.shop2.evinrude.com

 

http://shop2.evinrude.com/Index.aspx?siteid=1&catalog_id=5&s1=beed2f251d9c5032822df12a69224af8

Edited May 25, 2010 by irishfield

[Chugger]

Thanks irish, I'll ahve a look.

[Fisherman]

Does the Primer bulb stay fairly stuff?

Unless your fuel pump is before the primer bulb, it will not stay real stiff. Mine gets pumped up a bit and then the motor fuel pump takes over and draws the gas from the tank. The rest of the time it's quite soft.

[BillM]

Unless your fuel pump is before the primer bulb, it will not stay real stiff. Mine gets pumped up a bit and then the motor fuel pump takes over and draws the gas from the tank. The rest of the time it's quite soft.

 

 

There's a pill for that

[Sinker]

Could also be carbon build up. I'm assuming this is a 2 stroke. Go to a NAPA dealer and pick up a can of seafoam. Put the whole can in a full tank of gas and taker for a rip. Should help some. Watch out for all the smoke.....its gonna be thick if you've never de-carbed that engine. Slow trolling is a big cause of unburnt oil, which leads to extra carbon build up, and lumpy idling. Giver a shot, it won't hurt anything.

 

S.

[solopaddler]

As soon as I read your post I thought adjust the idle.

Wayne I think you're on the right track.

 

Agree with the seafoam as well, especially if it's an older 2 stroke.

Even if the problem isn't caused by a carbon build up seafoam is a great idea. It really works.

Edited May 26, 2010 by solopaddler

[Chugger]

This is awesome stuff guys, i'm going to give it all a try and let you know how things work out for me. Thanks for all the tips. First step sounds to be fiddling witht he idle.

Cheers,

-Graeme

Edited May 26, 2010 by Chugger

[jimmer]

If your tank is caving, it doesn't sound like you have a leak in the gas line anywhere. Yes you are opening the breather/air screw, but is the hole clear. That ethenol is good at plugging tiny holes up.