86 4 winns mercruiser 140 stalls on quick trottle

[Tim Head]

Did complete tune up, changed fuel filter,fuel pump,installed water seperator,compression check good.Carb was rebuilt by marine mech, Cranks up & runs good on muffs but stalls when going on plane unless I ease throttle ever so slow, after planning out she runs like a champ.checked tank pick up & even ran gas out of seperat gas tank & problem still exsists. This boat has been a head ache for 3 years but I still love her.

 

[Bondo]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

Ayuh,... Accelerator pump, or the carb rebuild didn't work...
Sometimes old carbs can't be Rebuilt...

 

[Tim Head]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

I really don't have much confidence in the marine mech that rebuilt the carb due to past experiences.
It's a 2 barrell mercarb any suggestions on getting a reliable replacement. National Carberuetor doesn't have any cores but will rebuild mine for 149.00.Should I take a chance & have mine rebuilt again?
Thanks for all the help recieved on this forum.

 

[HT32BSX115]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

It does sound like your carb is not squirting fuel on acceleration.

With the engine off, did you look in in the carb and open the throttle slowly (idle-WOT) to see if it squirts a nice steady stream of fuel?

 

[Tim Head]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

It does sound like your carb is not squirting fuel on acceleration.

With the engine off, did you look in in the carb and open the throttle slowly (idle-WOT) to see if it squirts a nice steady stream of fuel?

Got my 1st mate to open throttle & carb does squit a good stream fuel into both barrells,with engine off.

 

[Tim Head]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

Bought a newly rebuilt rochester carb off internet for 260.00 but had to modify linkage & make new fuel line. Engine cranks up with throttle opened up but can't get it to idle in neutral.I tried adjusting the 2 idle screws with muffs on for about 1/2 hour.I've read some post on how to adjust but I'm not having much luck.I'm not ready to throw in the towel just yet.I've been adjusting the 2 idle screws at the same time,with the same turns.I've had the screws adjusted in several positions but can't find the sweet spot.

 

[Fordiesel69]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

Other than the idle problem, how does it run at low speeds? It is possible your throttle linkage is wrong. I pulled the top off my rochester and when reassemble I had I rod backwards. I dont; remember which one but it idled smooth if I held the throttle linkage up a bit. I removed again and got it right.

Secondly merc spec is 1-1/4 open on the idle jets. Mine runs perfect at 1 turn open. The extra 1/4 makes it idle rough.

 

[fishrdan]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

There are 3 screws you need to adjust for idle, 1 is the idle speed and the other 2 are for idle "mixture". The idle speed screw is by the throttle arm, it's what stops the throttle arm. You have discovered the other 2, idle mixture screws.

It's a balancing act adjusting idle and you will have to adjust each screw multiple times. Idle speed, mixture screws, idle speed, mixture screws, etc, etc. First set your idle mixture screws out 1 1/2 turns, start engine and adjust idle speed screw to 600-700RPM. Slooooowly turn each idle mixture screw until it starts loosing RPM, then go back out about 1/8 turn. Adjust idle speed again, adjust idle mixture again by turning out a bit, then sloooowly in again until RPM drops, then back off a touch. You will have to play with the idle mixture screws in-out and if it's stumbling real bad you might have to clear the carb by increasing RPM's a bit with the throttle.

So now it's running perfect in the drive way, right? It's probably not going to run perfect out at the lake, while idling in gear as the engine now has a load on it. Now you have to go through the same procedure, out at the lake, with the engine warmed up, idling, while in gear. If it's not busy, I'll tie to the dock and run through the idle adjustments again.

 

[Tim Head]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

Thanks fisherdan,got it adjusted.The idle RPM is 750 but it's pretty smooth & at least she cranks without any throttle. Will lake test next week on vacation.

 

[fishrdan]

Re: 86 4 winns mercruiser 140 stalls on quick trottle

If it's idling at 750 on the muffs, that's probably OK as the spec is (I'm pretty sure) 600-700RPM, while the boat is in the water, engine warmed up and idling in gear. It's going to drop some RPM's with the extra load, so you should be fine.