Still having can't get 15hp to idle

[yellowtail]

Not sure where my post disappeared to, but to continue, Yellowtail is still having problems with 2007 15MSH.

Despite having had the carb off four times now, jamming wires and spraying cleaner everywhere, the engine refuses to idle without consistently pushing the choke in and out. When the revs come up, I jam it into gear and blast off.

There’s the odd thing: I take the motor ashore and put it in a 55 gallon drum (twice now), and it purrs like a kitten. Stick it back on the inflatable and I can’t get away from the dock.

The only difference I can tell is the fuel, the tank, and the hose.

Fuel is fresh in both my tank and the gallon jug next to the 55-gallon drum. I took my fuel tank apart and blew through the fittings, same with the longer fuel hose in the inflatable. Pumped fuel through and check a sample: clean, no water. I swapped out my inline fuel strainer for a new one. I fed the fuel hose directly to a jerry can of gas with a hose 12-inches long, (thinking fuel pump). The engine still will not idle!

I can only conclude my problem is not with the fuel system. Why it works ashore and not on the inflatable is anyone’s guess.

Any further words of wisdom would be much appreciated. I’m truly baffled.

Thank you…
Bry

[99yam40]

are you dunking the lower unit the same depth in the drum as it sits on the boat?
That will change the back pressure on exhaust some

[robert graham]

Maybe remove the idle mixture screws and shoot some carb cleaner in there and then some jet of air....replace screws and set to number of turns out from lightly seated....this little trick worked on my C90 when it quit idling...must have been a bit of dust or debris in there I guess, but it fixed it!....Good Luck!

[yellowtail]

Thanks guys. Yes the water level is pretty close and I've had the idle screw out several times and squirted the carb cleaner in the hole, plus dismantled the carb and soaked it for six hours. That does not seem to be the problem.
But thank you both...
Bry

[boscoe99]

If someone pumps the primer ball to keep it firm while you try and use the motor what happens? Same thing, worse or better?

Oh, removing a carburetor and spraying rodnut brand mechanic-in-a-can through it is not the same as cleaning a carburetor.

[rodbolt17]

rodnut is 55 yrs old
rodnut did his first carb on a 5hp techumseh when he was 8 yrs old.
the same summer I changed a broken connecting rod.
rodnut has never used an ultra sound cleaner.
simply a dip basket back in the day they actually had a chemical or a spray can.
rodnut has probably built more Q-jets,monojets two barrel rochesters,Holleys,solex's, SU carbs and webers than any two posters has probably actually seen.
we wont even go into model airplane stuff.

rodnut has done this for a living since he was 15.

rodnut has seen vehicles with manual advance magneto's and floor mounted starter pedals and 6v positive ground systems.

rodnut thinks that by activating the choke to make it run that you have fuel in the bowl and by activating the choke you bypass the pilot fuel and main circuits and force it rich.
rodnut thinks you still have pilot fuel issues.
you could have an idle relief issue but when you activate the choke it should get worse not better.

[yellowtail]

Thank you all...
Well I will be the first to admit that I know nothing of pilot fuel issues or idle relief issues. But interested to learn.

Boscoe, no... pumping the fuel line bulb makes no difference and there are no tears in the fuel pump diaphragm.

Someone here said pulling out the choke also advances the spark. Anything there to consider? And yes, I have had the carb in pieces as you suggested and reamed the orifices with a wire.

I'm thinking this is NOT a fuel problem but I have carb rebuild parts coming.

Anything else I should be considering. Coils?

Bry

[99yam40]

did you pull the plug to get to #2 pilot screw?
and did you set it back to specs in service manual when you put it all back together?

I do not remember seeing a choke that advanced timing before.
If it runs fine in the drum, I would be hooking up the fuel tank you used while in drum to see if you can get it to run well on the boat

[yellowtail]

Yes 99... yes... and yes... and yes.

Go figure? I'm completely baffled, and so are some "Good ol' boys" around here who have been working on outboards forever!

I have cleaned or changed out everything including the fuel line.

It can't be fuel related...

Thanks for your reply...
Bry

[TownsendsFJR1300]

Pushing the choke in and out CONFIRMS a fueling issue..

If it idles in the barrel just fine(with the different tank/ fuel line, I doubt the carb is the issue

Put your ENTIRE BOAT "set up" in the barrel, INCLUDING the boat TANK AND LINE, connectors, etc.


It'll behave badly again. Now you look for any air leaks, clogged tank filter, etc as THAT is the ONLY time it acts up..

[rodbolt17]

yep.
bubbas an outboards.
my ex wife's cousin had an uncle that fixed a tractor onced.
I still got da cresant wrench and vise grips.

if it runs well in the tank with a different fuel source but wont run on the boat you most likely have a fuel issue or idle relief port issue.

[yellowtail]

Thanx guys...
New fuel, new fuel line, different fuel tank, new fuel strainer, spotlessly clean engine fuel filter, new plugs, carb is as clean as a whistle with no sign of water or dirt.

Boy!

What else is there?

Bry

[TownsendsFJR1300]

Thanx guys...
New fuel, new fuel line, different fuel tank, new fuel strainer, spotlessly clean engine fuel filter, new plugs, carb is as clean as a whistle with no sign of water or dirt.

Boy!

What else is there?

Bry

Okay....

Does that mean it runs (or not?), you did or didn't run EVERYTHING (WHAT IS/WAS ON THE BOAT) IN the water tank?

Or you yanked the carb again re-cleaned?

[yellowtail]

Okay... the motor runs. From cold or hot start I have to pull the choke. I set the throttle at about one quarter. It starts on the third or forth pull and revs up but starts to die. I push the choke in and it revs up but starts to die again. I pull out the choke and immediately push it back in. Revs come up and start to die. I keep working the choke to keep the engine going.

When I'm untied, it work the choke and as the revs come up I jam the engine in gear and take off. If I miss it and put it in gear as the revs are going back down, it stalls. Once I am off and the engine comes up to speed, it seems to run well.

I've had the carb off for dismantling and cleaning four times now. When I originally removed the pilot screw, it was set 3-1/4 turns from the seated position. I have adjusted that to match what is in the manual but didn't notice any improvement.

I am thinking of going through the whole procedure again for setting the idle. I can't think of anything else...

Thank you everyone,
I truly appreciate the time you've put into this...

[99yam40]

Does it start and idle fine while in the drum still?