2005 300 da fuel problem

Oahu SR 300

New Member
Feb 1, 2019
6
Oahu, Hawaii
Boat Info
2005 300DA, Mercruiser 5.0’s Bravo III
Engines
Twin 5.0 MPI Bravo III MCM Stern Drives
hi guy having a hard time with my port 5.0 mpi Engine I can’t tell if I’m having an air problem not getting enough gas or that has something to do with the tank and the built-in in line pick up tube. I changed all the fuel filters and fuel pressure regulator’s and the cool fuel pumps seem to be working fine so I’m lost. The engine starts for a minute and then seems to not either get fuel or run strong enough then shuts off . the week before it ran perfect so I’m lost The gas is 2 years old but I add booster and added a lot of new fuel and runs fine specially for the other engine ??????????
 
In your 300 do your engines pull from separate tanks? Do you have the ability to switch which tank each engine draws from? If so this would be an easy way to determine whether or not the fuel is the problem. 2 years old is not ideal, especially if you're running ethanol blend, but I'm sure others have survived longer.
 
Yes it drawers from two separate tanks that’s a good idea I will try it tomorrow I will pull the port engine fuel line over to the working starboard fuel tank
 

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IAC? If you advance the throttle and then try to start it does it run? did the problem start after the fuel filter change - airlocked? are you sure its not ignition related? when was it last tuned up?
 
If you are running plain ethanol 87 you really need to stop that. Use non oxy premium. That’s all our marinas sell. Yeah it costs more but it lasts longer and doesn’t go through phase separation.

If your gas is 2 years old it’s time to purge it completely. Installl new filters and non oxy premium.

We use this in our older classic cars. Many of these are not driven very far or very often. I drive mine a lot however. I use the non oxy premium in the 77 el Camino but I do use 87 in the 94 Buick RoadMaster wagon . It’s made for this however with the plastic fuel lines and EFI.

I found this out the hard way a number of years ago. I did a test last year. It takes only about 8 weeks for phase separation in 87 gas. Once that happens it’s pump out time or you will have all kinds of motor problems.

It hold for small engines at home too. Even you old John Deere garden tractor needs the non oxy premium if you don’t use it often or store it for the winter.
 

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