Mercruiser 8.1 running rough

[ewood]

I have a 2008 350 DA with 8.1 v-drives with 220 hrs. My starboard engine has had a lot of fuel issues this season. They have replaced my high and low pressure fuel pumps, cleaned the injectors, and replaced the fuel regulator. The fuel pressure was 58 yesterday after idiling. It will only get up top about 3700 RPM's. I'm getting very frustrated!! Any help would be greatly appreciated.

 

[fc3]

What's the fuel rail pressure at 3700 RPM?

 

[ewood]

I don't know. I took the boat out for a run, and could only get the RPM's up to 3700.

 

[fc3]

Could be anything. Fuel, internal engine issues, ignition timing. It's a wild guess

 

[ewood]

thx!

 

[mainstream]

I have an 09 350 had the same issue plugs and wires fixed me up good luck

 

[Jimmy Buoy]

+1 on the plugs!

 

[gerryb]

Hey Eric. Good meeting you yesterday at "EDOCK". I hope you get some good ideas from other board members.
Regarding the plugs, you did say they were already replaced right? I had a similar issue on my '04 280 with 5.0s and it ended-up being a bad fuel filter -not the water sep filter but a stainless steel in-line fuel filter.

 

[ewood]

Gerry,

Good meeting you too. Thanks for the tip on the plugs. I'll be spending my morning at Marinemax trying to light a fire. We'll get this fixed. I hope!!

 

[scoflaw]

58 lbs. of pressure is an indication of flaking paint in the CF3 unit plugging up your fuel regulator
lots of talk about this here

 

[ewood]

They replaced the fuel regulator. That was their initial though, but no luck. Thank you for the input.

 

[Crushin It]

Scoflaw is referring to the Cool Fuel filters.... search that topic

 

[scoflaw]

They replaced it, but your fuel pressure is at 58, which means you still have the same issue. Did you replace the CF3 unit? Did they clean the filter upstream? Was it paint? Are they giving you an explanation why your fuel pressure is higher than it should be?

 

[ewood]

All good points. I will follow up today with the dealer. I appreciate the feedback.

 

[ewood]

So after a long week, they found that one of the fuel injectors was broken. In the process, they cleaned the CF3 and replaced the fuel regulator. She seems to be running well, with both engine RPMs up to between 4500-4600. Thank you for all the input.