2005 Bayliner 175 Mercury 3.0 Mercruiser i/o - Stalling

[Jess_newbie]

The boat starts up no problem – runs beautifully… as long as it’s at 1k rpm’s.
The second you pull back to resting idle… it’s stalls.

If you can get it engaged and slowly get it up to speed (without it conking out) it will run beautifully.

Once warmed… it could go into neutral and idle good… but then when ya wanna go… it conks out again.

Check gas for water, none.
Replaced fuel filter (old was crushed/and corroded)
Replaced Fuel Water separator filter
Stabilizer added to fuel

Next will spray carb cleaner

Don’t know what else it could be? Any help/suggestions?

 

[Scott06]

Sounds like you need a carb rebuild. Save the carb cleaner for when you get the carb apart as you need to clean the inside passages. Likely your idle mixture passages are clogged with debris.

Would also take the fuel filter off and check it for water and debris. On most 3.0's this is in the bowl on the bottom of the fuel pump.

 

[Jess_newbie]

Sounds like you need a carb rebuild. Save the carb cleaner for when you get the carb apart as you need to clean the inside passages. Likely your idle mixture passages are clogged with debris.

Would also take the fuel filter off and check it for water and debris. On most 3.0's this is in the bowl on the bottom of the fuel pump.

Thank you - hoping it's not going to be a rebuild. I replaced the small fuel filter and I'm waiting for the can filter to come in to replace the fuel separator filter. Also bought some Stabile carb/gas cleaner to add to the tank. Maybe it'll clear up some gook if it's in there.

Wondering if it could be timing?
Or - interrupter switch?
Will look at the idle set screw as well. I understand I have to put the boat in the water to properly get the pressure.
running out of ideas. Will play around more one night this week or weekend. Would really like to get it out on the water before summer ends!

 

[Scott06]

Thank you - hoping it's not going to be a rebuild. I replaced the small fuel filter and I'm waiting for the can filter to come in to replace the fuel separator filter. Also bought some Stabile carb/gas cleaner to add to the tank. Maybe it'll clear up some gook if it's in there.

Wondering if it could be timing?
Or - interrupter switch?
Will look at the idle set screw as well. I understand I have to put the boat in the water to properly get the pressure.
running out of ideas. Will play around more one night this week or weekend. Would really like to get it out on the water before summer end

A rebuild is cheap and easy to do. stop wasting money on fuel cleaners generally only will lighten your wallet.

Interrupt switch is only coming out of gear.
You can try turning idle speed crew in a hair to bump up idle speed , can try turning idle mix screw to see if it responds. Get a factory manual so you can see the tune up procedure, yes check ignition timing, but unless someone moved it or the clamp is loose generally doesn't move around a lot

 

[Jess_newbie]

A rebuild is cheap and easy to do. stop wasting money on fuel cleaners generally only will lighten your wallet.

Interrupt switch is only coming out of gear.
You can try turning idle speed crew in a hair to bump up idle speed , can try turning idle mix screw to see if it responds. Get a factory manual so you can see the tune up procedure, yes check ignition timing, but unless someone moved it or the clamp is loose generally doesn't move around a lot

Your suggestion on where to purchase a rebuilt carb?

 

[Scott06]

Your suggestion on where to purchase a rebuilt carb?

dont get a rebuilt carb - get a carb kit from mikes carb parts and rebuild it yourself.

I used a ultrasonic cleaner from harbor freight filled with carb cleaner for the parts cleaning

 

[Jess_newbie]

Got a kit and rebuilt/cleaned carb.
Runs beautifully- until you give it gas and then bring it back to idle. Conks out.

Got some Seafoam gas/carb treatment - replaced fuel filter and fuel/water separator filter.

Adjusted the idle screw to 1k.

Still having the same problem.
No smoke or anything from exhaust- idles nicely at 1k and sounds good.

I am at a loss.
Any other suggestions before I drop off at marina for a very expensive fix?

 

[Scott Danforth]

Did you clean the accelerator pump circuit? Did you pass a bit of fishing string thru the passages to make sure they are clear?

 

[Scott06]

How did u set the idle mix screw?

When you stab the gas are u getting a good stream of accelerator pump shot ?

What did contents of fuel filter look like

Did u set the ignition timing

 

[Jess_newbie]

Did you clean the accelerator pump circuit? Did you pass a bit of fishing string thru the passages to make sure they are clear?

Haven’t heard of that one. Will have to look it up. Will try anything!

How did u set the idle mix screw?

When you stab the gas are u getting a good stream of accelerator pump shot ?

What did contents of fuel filter look like

Did u set the ignition timing

Turned with a screw driver. - 1rpm if it goes down to 800 it stalls
Acceleration seems fine. It’s when ya back off.
File filter was crushed and yellow/brittle.
No on ignition timing.

 

[Scott06]

Haven’t heard of that one. Will have to look it up. Will try anything!

Turned with a screw driver. - 1rpm if it goes down to 800 it stalls
Acceleration seems fine. It’s when ya back off.
File filter was crushed and yellow/brittle.
No on ignition timing.

I mixture screw not idle speed screw. Idle mix screw is on throttle plate turning it in allows less fuel at idle turning it out allows more fuel at idle.

The idle speed screw you reference is the stop that the throttle seats against this determines how far the throttle plates are open at idle.

These are two different adjustments that both need to be tweaked during a time up

Since you didn’t mention setting idle mixture I’m assuming it is not tuned in. A good place to start is 1.5-2 turns out from lightly seated. Google it and you will find some YouTube videos on it


If turning the idle mixture screw in or out doesn’t change idle quality and speed then the idle circuit is plugged. By setting idle speed to 1000 rpm you are idling on the off idle transition circuit. So this likely indicates you are too lean at idle and it dies out or idle circuit is plugged.

Fuel filter being crushed sounds like it was installed incorrectly . If ignition timing is way off it could affect idle too

 

[Scott Danforth]

Idle mix screws are usually out between 3/4 turn and 7/8 turn on a Holley and a bit more than a turn out on a mercarb

Idle speed is a different screw