Mercruiser Only Runs If I Pump The Throttle.**UPDATE**

[Alpheus]

I am in the process of getting my boat in the water and I am running into a problem with my port engine. This engine is on a 1987 Sea Ray Sundancer 270 with twin Merc 260's and Rochester Quadra Jet carbs.I can pump the gas a couple of times and the engine will fire right up idle for a second and quit. I can pump it up again and re start engine and as long as Im pumping the gas the engine will continue to run,but not well. I think that it continues to run just because when Im pumping the throttle its just running using the gas thats being squirted in from the accelerator pump. The faster I pump the throttle the higher the engine will rev, but as soon as I quit pumping the gas she just quits. She is starving for fuel. I can see the fuel spraying into the carb from the accelerator pump when I pump the gas so I know fuel is getting to the carb, but just not enough to keep her running. Could this be a fuel pressure problem? I read on how to check the fuel pressure on the boat side but what should the pressure be from the fuel pump to the carb? Any help would be greatly appreciated...

 

[zbnutcase]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

Chances are good its due for a carb overhaul, especially if it has been sitting a while. 'nutcase

 

[180shabah]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

rebuild the carb.

 

[Bondo]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

Ayuh,... My guess is, the Carb is Junk...

 

[Alpheus]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

So the post in the DIY section thats starts out by saying:

A lot of you folks out there seem to be tearing into carbs quite a bit. Before you choose to open up a carb, you really need to look at what's feeding the carb first, and that is the boats fuel system.

Means nothing??? I think I will start by checking the fuel pressures and the filters first. I just asked because I wanted to see if this was common and if anyone knew a trick to fix it without just throwing parts at it and keeping my fingers crossed...

 

[Bondo]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

Means nothing???

Ayuh,... It means Alot,... Diagnostics are something Best done standing over the motor...
All We can do is diagnose with the Info you post,...From what you've said,...
The carb Is getting gas, it just Ain't managing it properly....
The Low speed circuit of the Carb it totally Plugged....
For a 20 year old Rottenchester, To Me,... It's Junk,+ needs Replacing...
But, I suppose you can Try rebuilding it...

 

[ErieRon]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

Go to the link below and download the manual for your engine. Section/Page 5A-2 shows the fuel pump pressures for the different style pumps used.

http://www.4shared.com/file/116242421/3c9db47f/mercuiser_9_setvice_manual.html

 

[John_S]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

Check your idle mixture screws to see if someone didn't inadvertly turn them all the way in, and not turn them back to the default setting. If the choke wasn't working, and you had cold weather, the pumping should have been able to keep it running long enough to warm up to run.

Bondos 100% correct, you are getting enough gas to the carb, or the accel pump wouldn't be getting fuel.

 

[Alpheus]

Re: Mercruiser Only Runs If I Pump The Throttle.

Re: Mercruiser Only Runs If I Pump The Throttle.

To start I did download the manual a couple of weeks ago. I always start a new project with alot of reading.

I went to the boat today and started off by checking all of the filters and tried running the engine from a remote fuel source,didn't work. I then swapped the carb from the good running engine just to confirm the bad carb idea and It ran the same way. I then went and bought a fuel pressure gauge from the Matco man who just happened to be at the marina and checked my pressure. It was reading almost 3lbs of pressure at 1500 rpm with me pumping the hell out of the carb to keep it running. I guess it had some pressure but not enough. I dont understand this because it has been my experience with car engines that once the bowls are filled the engine should still run until the bowls are empty. The sight tube to my pump has no fuel in it but I will install a new pump and see if this fixes the problem...

 

[Alpheus]

Re: Mercruiser Only Runs If I Pump The Throttle.**UPDATE**

after fixing the fuel pump I am now getting close to 7lbs of pressure the engine fired right up. I then put the original carb on and the same damn thing happened. I took the carb back off and tore it down and here is what I found.

This explains things. All of you guys that said it was the carb were right. I purchased a rebuild kit and just finished putting it back together. I will throw this carb on tomorrow and see how it goes...

 

[ben2017]

Re: Mercruiser Only Runs If I Pump The Throttle.**UPDATE**

dam, it looks like you were making candles in that thing.....hopefully it works out.

 

[Alpheus]

Re: Mercruiser Only Runs If I Pump The Throttle.**UPDATE**

I put the rebuilt carb on this morning and she fired right up. I only had to lower the idle a little and that was the only adjustment. I may have to make a couple out on the water, we'll see. Thanks for the help...