Mercruiser 3.0 will not idle after cranking

pachanga27

Seaman Apprentice
Joined
Dec 3, 2010
Messages
48
Engine is a 2005 Mercruiser 3.0
Engine S/N is OW350193
Has an Alpha1 outdrive...
The boat and motor has approximately 30 hours on it since new in 2005.

I have searched the forum for a similar situation but have not found any to be what I need to know.

Boat is a small runabout - and I can't remember the make and model - as basically I am trying to help a friend get this motor to run again.
Storyline - after being properly winterized - that is - all water drained via the plugs and the hoses that are part of the "owner serviceable" packaged on this motor.. the boat and motor have been sitting for 20 months. A long time. The motor was not fogged. Nothing was wrong or not working when the boat was pulled from the lake- Just has sat in the owner's driveway covered up for the last 20 months.

Now obviously - the impeller should be replaced - but more on that later. The problem is that the motor will not idle upon cranking. Before the owner talked to me - he used starting fluid sprayed into the carb - whereas the motor would fire and run for a few seconds before stopping - basically it was running on just the small amount of starting fluid. He calls me and asks if I can help - and I thought I would try.

I checked the obvious things first, frayed or broken ignition wires, found out it has 2 year old gas in the tank.. checked the fuel filter for water, checked to make sure fuel was being delivered to the fuel filter under pressure while cranking at the carb where the solid line connects to the carb and has a small filter. Drained some of the gas that was being pumped (while the motor was being turned over into a glass jar) for any dirt, water, ugly stuff, etc) and other than the gas smelled like gas - nothing out of the ordinary. Asked if he used regular pump gas - he said non-alcohol gas was used. So I tried cranking it. Nothing - not a rumble or any cylinder firing. Took the spark arrestor off... looked into the carb throat... it was dry as the sand in the desert. Hmm.. no gas in the carb throat. Pushed the button in to allow me to pump the throttle handle a few times to see if gas was being shot into the carb throat. Nothing.. no gas. So basically my thoughts are that the fuel is being delivered to the fuel filter on the carb... there has to be a stoppage somewhere. Looking at the service manual (boatinfo.no) for the 4 cylinder 3.0 motors - it shows a float bowl which of course first thing I wanted to do was to drain the bowl but there does not appear to be any way to drain it per se. I wanted to check to see if there was gas in the bowl.

Next step - which I am betting is not the proper way to do it... I pour raw gas into the carb throat. put the arrestor back on. Cranked and it fired right up and ran for approximately 5 to 10 seconds - which tells me that the electrics are working - spark plugs..etc. I did it again - and lo and behold - it ran again for 20 seconds.. but died. Basically just running on the gas I am supplying. So.. after a few more times of this.. I sat back ..said time to regroup and understand what is going on and how to fix it. BTW .. I got drenched from the hoses that are used to drain the block as the motor would run long enough to pump water through the motor as it was running on a muff ... that was not fun. I did the tell the owner - that the impeller will need to be changed since it has sat so long.

Gas is being supplied to the in-line filter at the carb., the little screen filter was clean. No gas being shot in to the carb when the handle is used (to pump) the gas to the carb. I looked at the service manual diagnostic steps - I am wondering if the float and needle which regulate the gas once it hits the carb is stuck "closed".
My problem is that if this was my boat - I would be into that in a heartbeat... but - I need to really to understand more about this carb than just looking at pictures before I attempt this on another person's motor. There are other passages in the carb that regulate the idle mixture that may be clogged with deposits as the gas evaporated over the 20 months.

Does anyone have any thoughts as to how I can check or correct this issue without removing the carb?
 
Last edited:

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,701
Engine is a 2005 Mercruiser 3.0
Engine S/N is OW350193
Has an Alpha1 outdrive...
The boat and motor has approximately 30 hours on it since new in 2005.

I have searched the forum for a similar situation but have not found any to be what I need to know.

Boat is a small runabout - and I can't remember the make and model - as basically I am trying to help a friend get this motor to run again.
Storyline - after being properly winterized - that is - all water drained via the plugs and the hoses that are part of the "owner serviceable" packaged on this motor.. the boat and motor have been sitting for 20 months. A long time. The motor was not fogged. Nothing was wrong or not working when the boat was pulled from the lake- Just has sat in the owner's driveway covered up for the last 20 months.

Now obvisously - the impeller should be replaced - but more on that later. Te problem is that the motor will not idle upon cranking. Before the owner talked to me - he used starting fluid sprayed into the carb - whereas the motor would fire and run for a few seconds before stopping - basically it was running on just the small amount of starting fliud. He calls me and asks if I can help - and I thought I would try.

I checked the obvisous things first, frayed or broken ignition wires, found out it has 2 year old gas in the tank.. checked the fuel filter for water, checked to make sure fuel was being delivered to the fuel filter under pressure while cranking at the carb where the solid line connects to the carb and has a small filter. Drained some of the gas that was being pumped (while the motor was being turned over into a glass jar) for any dirt, water, ugly stuff, etc) and other than the gas smelled like gas - nothing out of the ordinary. Asked if he used regular pump gas - he said non-alcohol gas was used. So I tried cranking it. Nothing - not a rumble or any cylinder firing. Took the spark arrestor off... looked into the carb throat... it was dry as the sand in the desert. Hmm.. no gas in the carb throat. Pushed the button in to allow me to pump the throttle handle a few times to see if gas was being shot into the carb throat. Nothing.. no gas. So basically my thoughts are that the fuel is being delivered to the fuel filter on the carb... there has to be a stoppage somewhere. Looking at the service manual (boatinfo.no) for the 4 cylinder 3.0 motors - it shows a float bowl which of course first thing I wanted to do was to drain the bowl but there does no appear to be any way to drain it per se. I wanted to check to see if there was gas in the bowl.

Next step - which I am betting is not the proper way to do it... I pour raw gas into the carb throat. put the arrestor back on. Cranked and it fired right up and ran for approximately 5 to 10 seconds - which tells me that the electrics are working - spark plugs..etc. I did it again - and lo and behold - it ran again for 20 seconds.. but died. Basically just running on the gas I am supplying. So.. after a few more times of this.. I sat back ..said time to regroup and understand what is going on and how to fix it. BTW .. I got drenched from the hoses that are used to drain the block as the motor would run long enough to pump water through the motor as it was running on a muff ... that was not fun. I did the tell the owner - that the impeller will need to be changed since it has sat so long.

Gas is being supplied to the in-line filter at the carb., the little screen filter was clean. No gas being shot in to the carb when the handle is used (to pump) the gas to the carb. I looked at the service manual diagnostic steps - I am wondering if the float and needle which regulate the gas once it hit s the carb is stuck "closed".
My problem is that if this was my boat - I would be into that in a heartbeat... but - I need to really to understand more about this carb than just looking a pictures before I attempt this on another person's motor. There are other passages in the carb that regulate the idle mixture that may be clogged with deposits as the gas evaporated over the 20 months.

Does anyone have any thoughts as to how I can check or correct this issue without removing the carb?

You either have a clogged line or filter, or ..... the more probable cause is you need a fuel pump. Below is your fuel supply system setup
http://www.mercruiserparts.com/Show_...+Supply+System

Disconnect the line at the carb and put it in a container to see if fuel comes out when you crank it
 
Last edited:

BRG25

Chief Petty Officer
Joined
Jul 13, 2001
Messages
528
I agree with AllDodge...sounds like the carb is not getting fuel. I personally wouldn't run it with 2 year old gas. I would set up a temporary remote tank with fresh gas while you troubleshoot.
 

pachanga27

Seaman Apprentice
Joined
Dec 3, 2010
Messages
48
I performed the test where I disconnected the fuel line at the carb. The brass nut first - then cranked the motor over and the fuel pump pumped a pint of gas out in a very short period of time. That said to me the fuel pump is working. Then I removed the small screen which resides in the carb body where the brass coupling fits inside the filter coupling ... checked the filter again... all clear. Reinstalled the fuel line. Cranked the motor again. Started removing the brass coupling again. Got sprayed with gas that was under pressure from just cranking the motor as the nut was loosened. thank goodness for safety glasses and no spark ... cause I would have looked like a human Tiki Torch with burning eyes as I ran around the yard. Ok.. so back to troubleshooting once again... looking into the bowl as my assistant cranks the motor and pump the accelerator handle - no fuel being sprayed into the carb. At this point .. I may just suggest to my friend to take the boat to a mechanic... I am not comfortable with taking the carb off. My boat... no problem...someone's else's boat... problem. Since gas is not getting past the fuel inlet or into the carb ... the issue (to me) has to be a stuck needle in the float bowl so there is no gas for the pilot circuits to pick up as it cranks. And yes - siphon all the old gas out and put in fresh gas. Thanks for the replies.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,701
I performed the test where I disconnected the fuel line at the carb. The brass nut first - then cranked the motor over and the fuel pump pumped a pint of gas out in a very short period of time. That said to me the fuel pump is working. Then I removed the small screen which resides in the carb body where the brass coupling fits inside the filter coupling ... checked the filter again... all clear. Reinstalled the fuel line. Cranked the motor again. Started removing the brass coupling again. Got sprayed with gas that was under pressure from just cranking the motor as the nut was loosened. thank goodness for safety glasses and no spark ... cause I would have looked like a human Tiki Torch with burning eyes as I ran around the yard. Ok.. so back to troubleshooting once again... looking into the bowl as my assistant cranks the motor and pump the accelerator handle - no fuel being sprayed into the carb. At this point .. I may just suggest to my friend to take the boat to a mechanic... I am not comfortable with taking the carb off. My boat... no problem...someone's else's boat... problem. Since gas is not getting past the fuel inlet or into the carb ... the issue (to me) has to be a stuck needle in the float bowl so there is no gas for the pilot circuits to pick up as it cranks. And yes - siphon all the old gas out and put in fresh gas. Thanks for the replies.

I think you have a handle on the problem with the stuck needle seat. You could blow some air (15 to 20 psi) into the fuel line fitting going into the carb to see if it would free it up, but best would be remove and clean.

You mentioned previously that the tanks has non-ethanol gas in it. If that is the case the gas may be OK, also mentioned it smelled like gas, nothing different. I would suggest fixing the carb issue first before you start pumping fuel out.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,138
Engine is a 2005 Mercruiser 3.0
Engine S/N is OW350193
Has an Alpha1 outdrive...
The boat and motor has approximately 30 hours on it since new in 2005.

I have searched the forum for a similar situation but have not found any to be what I need to know.

Boat is a small runabout - and I can't remember the make and model - as basically I am trying to help a friend get this motor to run again.
Storyline - after being properly winterized - that is - all water drained via the plugs and the hoses that are part of the "owner serviceable" packaged on this motor.. the boat and motor have been sitting for 20 months. A long time. The motor was not fogged. Nothing was wrong or not working when the boat was pulled from the lake- Just has sat in the owner's driveway covered up for the last 20 months.

Now obviously - the impeller should be replaced - but more on that later. The problem is that the motor will not idle upon cranking. Before the owner talked to me - he used starting fluid sprayed into the carb - whereas the motor would fire and run for a few seconds before stopping - basically it was running on just the small amount of starting fluid. He calls me and asks if I can help - and I thought I would try.

I checked the obvious things first, frayed or broken ignition wires, found out it has 2 year old gas in the tank.. checked the fuel filter for water, checked to make sure fuel was being delivered to the fuel filter under pressure while cranking at the carb where the solid line connects to the carb and has a small filter. Drained some of the gas that was being pumped (while the motor was being turned over into a glass jar) for any dirt, water, ugly stuff, etc) and other than the gas smelled like gas - nothing out of the ordinary. Asked if he used regular pump gas - he said non-alcohol gas was used. So I tried cranking it. Nothing - not a rumble or any cylinder firing. Took the spark arrestor off... looked into the carb throat... it was dry as the sand in the desert. Hmm.. no gas in the carb throat. Pushed the button in to allow me to pump the throttle handle a few times to see if gas was being shot into the carb throat. Nothing.. no gas. So basically my thoughts are that the fuel is being delivered to the fuel filter on the carb... there has to be a stoppage somewhere. Looking at the service manual (boatinfo.no) for the 4 cylinder 3.0 motors - it shows a float bowl which of course first thing I wanted to do was to drain the bowl but there does not appear to be any way to drain it per se. I wanted to check to see if there was gas in the bowl.

Next step - which I am betting is not the proper way to do it... I pour raw gas into the carb throat. put the arrestor back on. Cranked and it fired right up and ran for approximately 5 to 10 seconds - which tells me that the electrics are working - spark plugs..etc. I did it again - and lo and behold - it ran again for 20 seconds.. but died. Basically just running on the gas I am supplying. So.. after a few more times of this.. I sat back ..said time to regroup and understand what is going on and how to fix it. BTW .. I got drenched from the hoses that are used to drain the block as the motor would run long enough to pump water through the motor as it was running on a muff ... that was not fun. I did the tell the owner - that the impeller will need to be changed since it has sat so long.

Gas is being supplied to the in-line filter at the carb., the little screen filter was clean. No gas being shot in to the carb when the handle is used (to pump) the gas to the carb. I looked at the service manual diagnostic steps - I am wondering if the float and needle which regulate the gas once it hits the carb is stuck "closed".
My problem is that if this was my boat - I would be into that in a heartbeat... but - I need to really to understand more about this carb than just looking at pictures before I attempt this on another person's motor. There are other passages in the carb that regulate the idle mixture that may be clogged with deposits as the gas evaporated over the 20 months.

Does anyone have any thoughts as to how I can check or correct this issue without removing the carb?

Ayuh,.... It sounds like the carb needs to be Rebuilt,...

I donno of anyway to rebuild the carb, while on the motor,....

It needs a complete disassembly, cleanin', 'n be blown out with compressed air,...
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Tap on the side of the carb float bowl with the butt end of a screwdriver in an attempt to unstick the needle. If fuel is getting to the carb but not into it, the needle and seat are the problem. Once loose things should work normally although a rebuild after a 20 month layup would still be in order. Nothing wrong with 20 month fuel if there is no evidence of water. If the tanks is less than full, top off with fresh fuel.
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
Ayuh,.... It sounds like the carb needs to be Rebuilt,...

I donno of anyway to rebuild the carb, while on the motor,....

It needs a complete disassembly, cleanin', 'n be blown out with compressed air,...
That is what I was thinking too. It is cheap and easy.
 
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