Volvo Penta 2005 5.7 GXi-f 8cy won’t go over 3k rpms on load

[Simoncelia]

Hi There, any help much appreciated. Boat sat for 1 season: took it out and started right up. Fuel pump started making whining sounds and couldn’t get the boat over 5mph or 2500 rpm under load. In neutral I can get it way up there to 5k+rpm. Changed out fuel pump used external gas tank, changed spark plugs, brand new cap & rotor, checked ignition module, new fuel regulator, checked compressions getting perfect on all cylinders, no alarms, temp looks normal, after all this still can’t get it over 5-10 mph or 3k rpms under load . In neutral revs all the way up and idles perfectly. I’m stumped any help much appreciated!!! Please!! I’m losing it on what’s wrong.

 

[Simoncelia]

I also checked fuel pressure. 12 steady on the low pump and the high pressure between 50-60. However the high pressure is only steady on startup or in neutral with throttle, on load it flutters between 55-60

 

[alldodge]

What where the compression numbers?

 

[Simoncelia]

175-180 on all cylinders. Thank you

 

[alldodge]

That is high compression for a 350, should be in the 150 area, so either you have a bad gauge or have some liquid (water, gas, oil) in the cylinders.

If compression is good and there is nothing wrong with the drive (lube is changed, and rotates freely) then your probably going to need to get the motor scanned for codes.

When throttle handle is moved full forward, check to see if throttle body plates move full open

 

[Simoncelia]

It’s possible there’s fuel, engine is only 2 years old. Would it be my fuel injectors? Problem is I don’t have a Volvo Penta Dealer on my lake to run a diagnostic. Any ideas.. plenty of mercury dealers..

 

[Scott Danforth]

check your gauge. any compression reading above 150 is either a bad gauge or you have fuel, water, or oil in the cylinders.

your motor would rev to 5000 in neutral with only one of the 8 cylinders firing. so that test does absolutely nothing.

reasons for low WOT:
restricted fuel system
restricted exhaust system
plugged filters
bad plugs
bad fuel
bad distributor cap (specifically if you have the crab cap)
motor in limp-home
sticking anti-siphon valve.

 

[Simoncelia]

It’s possible there’s fuel as I didn’t disconnect the fuel pump.. what is a fix for this?

 

[alldodge]

You probably just have a bad gauge, try a different gauge. Place the throttle in full WOT when checking compression. Moving throttle to WOT when cranking, turns off fuel going to cylinders. Also disconnect power to coil, like turn man overboard kill switch off, and do crank over at least 4 times with each compression test per cylinder

 

[Simoncelia]

Ok awesome will try. What about running a diagnostic? I don’t have any Volvo Penta dealers close by; any way I can run it myself without spending too much $$?

 

[alldodge]

Wgat I'm seeing is a MEFI controller and it might be a 4, and if so you should be able to use the led and paper clip to get the codes.

muc can you assist?

If it is a MEFI 4 then use a paper clip and led then turn key to ON without starting. Then count flashes

 

[Simoncelia]

Thank you!! Awesome I’ll try that. I just had the fuel injectors sent out to get cleaned just in case.. Also another concern. The high fuel pressure flutters between 50-60psi and doesn’t stay steady.. is that an issue? Maybe just a bad gauge but it’s brand new and the low side stays steady 12.

 

[Scott Danforth]

Yes, fuel pressure should be steady

 

[Simoncelia]

What do you suggest? Could it be bad fuel injectors? I replaced the regulator and fuel pump.

 

[Simoncelia]

Here’s a video of the high pressure fuel gauge

 

[alldodge]

Was the distributor moved any at all even a slight bit? If not then that should not be the issue

The distributor cap is known to be an issue but since you replaced it and same issue, this to would be a non-issue

Was the gas pressure reading done under load on in neutral? If in neutral, take it under load
Is the flame arrestor clean (it can be seen through)?

 

[Simoncelia]

No distributor was not moved. I took the gas pressure under both neutral WOT and load. It was similar; the video was under neutral.

 

[Simoncelia]

The flame arrestor is the only thing I never took off. So I assumed it was clean.

 

[muc]

Wow, so many parts replaced! Did all this stuff test bad? What service manual are you using?

The little bit of needle bounce I see in your video wouldn’t worry me much. It looks like the gauge is just laying on the engine at high RPMs

i would think about doing an cylinder canceling test / power balance test. And see if your running on all 8 cylinders.

 

[Simoncelia]

Thank you! I’m picking up the fuel injectors tomorrow and hope to put them in. Will keep you posted. You guys are the best! Thank you all!!