Mercruiser 3.0LX 1995 Having trouble starting

[andrew123456789]

Hey there. I am looking for some help with my mercrusier 3.0LX 1995. The boat was sitting for about 2 years, I started with replacing all of the fluids including gasoline in the boat to crank it over. I could not get the boat to start. I then rebuilt the carburetor because the needle was sticking and i was not getting fuel into the carb. After my rebuild i got the engine to start for about 30 minutes and heat it up to temperature. The next day, i went to go start the boat, and it turned over and then died at idle. I then did the following:

Changed the Fuel Water Seperator
Changed the Fuel Filter on mechanical fuel pump
replaced the fuel line
Checked for gas flow with the line off of the carburetor and there was gas
I replaced the spark plugs
I checked the spark and compression at each cylinder and it was correct

I am not seeing any problems with getting gas into the carb while i am pumping the throttle, however i rebuilt the carb again after i could not get the boat to start.

This is what is happening: I will let the boat start early in the morning and then the boat will fire up and then immediately bog down. I will then try to start it again, and it will bog down faster, until it will not even try to crank over when turning the key.

Let me know any thoughts please!

 

[alldodge]

will not even try to crank over when turning the key.

Explain what you mean here. The motor does not turn over (starter not engaging) or it turns over but does not start?

 

[andrew123456789]

Starter turns the engine and crankshaft. Engine does turn over but does not start. When I start it first thing in the morning, the engine will start, however about 15 seconds after it starts, it will bog down. After that, it will bog down quicker after each try, until it does not start at all. Battery is also completely charged while this is happening.

 

[alldodge]

Take fuel line off the carb and place in a container, then crank the motor, it should pump out fuel quickly, figure how much came out

If it doesn't come out quick, disconnect the fuel line at the fuel tank. Then remove the barbed fitting from the tank. This is the antisiphon valve. If it gets clogged pump has a hard time pumping

Right now I'm thinking fuel pump

 

[andrew123456789]

alldodge. I have disconnected that line already and I am getting sufficient fuel out of the pump at the carburetor also at pressure of 7 psi. Antisiphon valve has not been cleaned. I will do this as my next step and see results. Would this cause the bogging down problem into a no start through over trying to start the motor 3-4 times?

 

[Rick Stephens]

The question now becomes is it too lean or too rich. Start it up, let it bog and die and pull the plugs and take pics of them. Black and wet, or white and dry.

 

[alldodge]

In this case have you checked to see if the carb is flooding when motor is running?

Look down the throat of the carb, see fuel dripping of pouring in?

 

[kenny nunez]

Are you sure that the float setting in your carburetor is not set too low? Also be sure that the filter in the carburetor is not installed backwards if it is the paper style.

 

[andrew123456789]

So a couple of things here. Spark plugs are as black as it can be. Not particularly wet. Carb is not flooding. I made sure to adjust the float to the correct measurement when I rebuild the carb. Filter is installed correctly in the carb. After my first rebuild I put it in backwards, and noticed after doing the second and installed it correctly.

it does not make sense to me how the motor will start when it sits overnight (then bogs down). And then will not even try to start after 4-5 try’s about 15 seconds apart.

 

[andrew123456789]

Another thing that is happening: when I let it sit and it starts, it is at idle speed and then the RPM will rise to about 3000 and then it will die

 

[alldodge]

Another thing that is happening: when I let it sit and it starts, it is at idle speed and then the RPM will rise to about 3000 and then it will die

Plugs black, its running real rich
Starts and speed increases at idle means it has a vacuum leak or is starting to flood and burning more gas till it floods out

Sitting over night allows fuel to evaporate. Check your oil level and if its not higher, see if it smells like gas

Its a carb issue

 

[andrew123456789]

I have been scrolling through here and thought about a possible timing issue. I have never played around with timing in any engine before. Is there any chance this could be due to a timing issue? Also fuel/air mixture screw? I did 1.5 turns as the manual states when reassembling the fuel/air mixture screw.

 

[alldodge]

The idle screws are only for idle and do next to nothing to keep the motor running above an idle

Don't see the current issue having to do with timing. It could be on target of off a bit and would not have effect for the motor to keep running without another issue showing up

 

[andrew123456789]

Thanks for the help everyone. Any recommendations on how to check for a leak in the carb? Trying not to spend $900 on a new one if possible