4.3 GXI-E rough idle

[GMTK]

2004 4.3 GXI-E. 189 hours. Freshwater only. Stored in dry dock.

Oil change, new impeller, new fuel filter al this spring. I use 93 octane from Exxon along with marine stabil and sea foam.

Has run great this year. Approximately 12 hours of use. Today started and it’s idling rough. Had fluctuating rpms while on plane. It’s almost like it’s missing.

Going to replace the plugs and wires. I have owned the boat four years and don’t know when/if the plugs were replaced.

Any other ideas or diagnosis on what I should do. And if anyone has plug and wire recommendations I would appreciate it.

 

[alldodge]

IMO your wasting money, only need 87 but your money your boat

Dump the fuel filter contents into a clear container to see if there is anything there but clear clean gas

Next thing is replace the distributor cap and rotor. The caps are known to have issues and can look fine but be bad. Probably don't need plugs or wires

If the cap doesn't fix the issue, suggest getting a fuel pressure gauge and measure it at the rail. Pull some plugs and see what they look like

 

[monster1]

Have you ever checked your fuel pressure regulator screen for contamination? The fuel pumps on these engines have been problematic. The manufacturer painted the insides of these pumps in the manufacturing process. The fuel interacts with the paint causing it to flake and contaminate the fuel system. It causes premature failure of these fuel pumps and also clogs the fuel pressure regulator screen on the fuel rail. Clean it out and reinstall. I'd also probably change out the distributor cap and rotor. They also give similar symptoms you are describing. The flat "crab style" caps aren't the best design. Make sure you go OEM on the cap and rotor.

 

[GMTK]

Pulled the fuel filter, looked good, 5-6 small black specs game out. The I pulled the fuel pressure regulator - it had never been pulled before based on the caked-on paint. Screen was filthy. In my attempt to get the screen of the regulator to clean it I broke it.... If anyone can help me find just the screen, I would appreciate it, a new regulator is $200.

 

[monster1]

You actually don't need the screen according to VP. There is a bulletin regarding replacing the screen with a c-clip. You can get the clip from a VP dealer or buy one from ebay.

https://rover.ebay.com/rover/1/711-...MIzsvB8NjL4gIVXbXACh0UOQTmEAQYASABEgIMAvD_BwE

 

[monster1]

I tried to provide a link to the VP service bulletin but for some reason it wouldn't provide a valid link. If you want more info, just search "volvo penta fuel pressure regulator service bulletin." All the info you need regarding this issue.

 

[GMTK]

Thanks to all. Got the clip ordered. Dumb question - why get rid of the screen? In my case, it obviously caught some debris. Found this on another site about the regulator:

"I THINK the way the regulator is plumbed in on these systems the regulator gets the fuel after its already run through the injector manifold - so it regulates pressure by controlling the flow back to the return line to the pump. If that's true then any flecks getting into that manifold would have had the opportunity already to get to the injectors."

 

[alldodge]

True, but the crud came from time and maybe so regular maintenance intervals (not replacing filter often enough). Can also come from just time and things getting old. This is why every so often folks need to clean carbs and fuel injectors.

While Merc doesn't remove the screen, it can cause more problems then it helps.

 

[monster1]

Not sure of the reason. Doesnt make sense to me either. I'd rather keep the screen and just make it part of yearly routine maintenance. Hope this helps your issue.