Merc 3.0 losses power and stalls at take off

[a251172]

Hi,
I have a 2007 19.5 stingray with a Merc 3.0 motor. when the boat is on the trailer running with the hose it seems to run perfect, will idle fine, put it in gear and it will continue to run fine, give it some throttle and it will be fine, back off and down to neutral and will continue to run fine. In the water however that?s not the case. It will still idle ok, and when I put it in gear it will go slow fine, but at take off it bogs down and stalls. IF you pump the throttle and can get past this point (over 2000 rpm's) it will run fine at all RPMs through WOT. Slowly backing off the throttle it will usually get to the point where it will run at all RPM's and go back to idle fine in neutral. However once you begin to take off again it will bog and stall between 1200 and 1800 rpms.

I am using fresh premium gas, have changed the plugs, replaced the fuel filter under the fuel pump and also cleaned the screen on the inlet to the Carb. That screen had some residue in it, so I am wondering if I am on need of a new carb or rebuild.

When I replaced the plugs the motor had ACDelco in it, I went to the local Marine shop and they looked up the RKG match and I am running those. Someone told me that I should have used the plugs that came out of it. Do you think that?s playing a role, I do trust this marine shop, it?s been around along time and I worked with the owner to get my plugs.

I was wondering why the problem does not exist on the trailer with the hose but occurs in the water. I have had the boat running several times on the hose and also in the water and it always performs the same, so I know its not a fluke that it just happen to run ok on the hose once.

I was also considering adding an additional fuel/water separator filter to the fuel line. I know the filter under the fuel pump is there and it also has a bowl that?s supposed to collect water, but it is very small. Wondering if a larger fuel filter/water separator would be a good addition to the boat.

Thanks for you thoughts in advance.

 

[gener8s]

Re: Merc 3.0 losses power and stalls at take off

Mine does something similar, it will stumble on "take off", but mine only does it once a day, the first time I hit the throttle. After that, it's fine the rest of the day. If I recall correctly, there is a check valve for the accelerator pump and it's slowly leaking down overnight. Your sounds like either your accelerator pump isn't working at all, or your intermediate jet is plugged. Pull your flame arrester and look down your carb while someone pumps your throttle to see if your getting a steady stream of fuel.

 

[cr2k]

Re: Merc 3.0 losses power and stalls at take off

Your accelerator pump is going out if not gone. With the engine OFF pull the flame arrester and while looking down the throat of the carb holding the choke open have someone pump the throttle. What you should see is 2 streams of fuel shooting in to the throat. What you probably see is one or two dribbles if that.

 

[a251172]

Re: Merc 3.0 losses power and stalls at take off

Your accelerator pump is going out if not gone. With the engine OFF pull the flame arrester and while looking down the throat of the carb holding the choke open have someone pump the throttle. What you should see is 2 streams of fuel shooting in to the throat. What you probably see is one or two dribbles if that.

I tried this and if someone pumps the throttle quickly i do see 2 steady streams of fuel, if they do it slowly, then nothing bit a dribble if that. DOes that sound like the accelerator pump?

 

[extremez]

Re: Merc 3.0 losses power and stalls at take off

mine was doing the same thing. I ran the questionable gas out of it, cleaned the carb down, put stabil marine ethanol additive in it, installed a water/fuel filter, changed both fuel filters.

Was doing great last week on fresh gas 87 octane. Took it out Sunday afternoon for a couple hours and it acted up again. Mine will do it even when steady increase of throttle. As soon as it gets to about 1600 rpm's it bogs and will try to stall. Have to catch it otherwise it will stall out.

With the top of the carb off I can work the accelerator pump up and down and get my 2 streams of fuel.

 

[bobhol]

Re: Merc 3.0 losses power and stalls at take off

Mine was doing that 2 weeks ago ...it was terrible and was stumbling out of the hole...I thought ...time for a tune up....when I came in I needed gas so went out and got a couple jugs ,filled it up and put in my Starbrite additive and that solved the problem ....next time out it was perfect ....maybe yours is the same ..good luck!!