Mercruiser 350 won't stay running

[1990blackgt]

Last fall I bought a new to me 1986 Century Mirada 25' aft cabin. I used the boat for 2-3 months with no problems. Engine ran fine. In November, the old outdrive on the boat let go. The boat was winterized, and dry docked. The boat was repowered, and retrofitted with a mercruiser 350 4 barrel engine the year before I bought it. Over the winter i replaced all bellows, and fitted a brand new SEI 106 outdrive. Now the engine won't stay running. If I pump the throttle 3-5 times before starting, the engine will start, and idle fine for a minute or less. If i try to give it throttle most of the time the engile will die. Other times it will rev a bit until it seems to run out of fuel. I have changed the fuel/water separater, and have emptied it, checking for water in fuel. It has 40 gallons of fresh 93 octane in the tank. The fuel pump is mechanical. The motor is a mercruiser 350 with a carter 4 barrel carb with an electric choke and thunderbolt IV ignition. When I manually open the throttle i can see fuel being squirted into the carb. The battery is brand new. The fuel lines have been checked, and are clear of debris. I'm truly at a loss. What can I do next? Any ideas/advice would be greatly appreciated.

 

[1990blackgt]

Fuel pump bad?

 

[Scott Danforth]

empty the contents of your fuel/water separator into a clear container to check for water. from what you are describing, it sounds like what you see being sprayed is a slight bit of fuel with a bit of water.

 

[1990blackgt]

Thanks Scott. I did this already, but i also filled the filter with fresh gas prior to installing it. Maybe it wasn't true results. I'll do it again after I get off work at 1pm this afternoon. I'll post a pic if i can figure out how. Lol.

 

[alldodge]

Howdy

Pull the fuel line off the carb and put it in a container. Crank the motor and see if you get a good supply of fuel.

Next smell the fuel to see if it smells like fuel

If all checks out, remove fitting off front of carb and check the filter behind it. Something like item 2 in link below

http://www.mercruiserparts.com/bam/subassembly/31727/1077/100

 

[1990blackgt]

Thanks Alldodge. I'll try that this afternoon. The link you sent does not have a picture for item #2. Could you explain?

 

[Rick Stephens]

Pulling the fuel line and pumping fuel into a clear container is a good check of the anti-syphon valve as well. Amazing how many times they get plugged up and overlooked.

Rick

 

[alldodge]

Thanks Alldodge. I'll try that this afternoon. The link you sent does not have a picture for item #2. Could you explain?

I can see it,don't understand why you are unable.

Not knowing the exact carb you have I guessing it's something like a quadrjet or similar. There should be a larger fitting which the fuel line screws into. This big nut/fitting will have a filter behind it and a spring

 

[1990blackgt]

At boat now. Pulled fuel line off carb, put it in a bottle, and cranked. Lots of fuel came out in spurts. Filled bottle halfway, let it settle, and no water in fuel. Emptied fuel/water filter, same result. No water.

 

[1990blackgt]

Boat has a thunderbolt iv ignition. Could this be a problem? I pulled spark plugs. They were sooty, and wet with gas, but otherwise fine.

 

[alldodge]

Boat has a thunderbolt iv ignition. Could this be a problem? I pulled spark plugs. They were sooty, and wet with gas, but otherwise fine.

Neither soot or wet is good, sounding more like no spark going on.

Here the TB-IV troubleshooting flow chart. Follow it and it should find your issue

 

[1990blackgt]

Thanks. According to the diagram you provided i need to replace the ignition sensor in the distributor. I have spark, but maybe not enough. I have fuel, and new plugs. I'll see if I can get one.

 

[alldodge]

Well you say it trys but then dies, so that could be the sensor or even your loosing power after the key is released. But the flow chart in most all cases works

 

[Mercruiser420]

Carb flooding? Floats adjusted? Does the carb keep dripping after the engine shuts off?

 

[1990blackgt]

Marina mechanic suggested rebuilding the carb. Having marina do that for me now. Will post results.

 

[alldodge]

Hope that does it but from the symptoms posted, I cannot see a carb problem

 

[grewvin1]

Bad Coil?

 

[1990blackgt]

Carb rebuild solved my problem. Runs like a champ now.

 

[alldodge]

Go figure, glad you got her going