Mercruiser 3.0 MPI 2016

[EBSTINGRAY]

Hi,
I have bought a used 2016 stingray 18ft with a mercruiser 3.0 MPI engine. I started having issues shortly after I got it. The engine fires up fine and runs idle fine, but once you rev it up a bit it sputters like it is pulsing instead of running smoothly. The mechanic and I have replaced every sensor and checked everything including the fuel quality ( I use pure fuel no ethanol) and all is fine, but I cannot find what the recommended fuel pressure is for this engine. The smartcraft works fine and reports no faults. However the engine keeps pulsing in and having a unstable RPM once you get over the idle RPM of 750. I am trying my luck here and see if anyone has the fuel pressure specs for this engine or experienced something similar.
Thanks, Eric

 

[alldodge]

Pressure should be 43 psi at 1800 rpm
Being an EC motor, do you have the engine serial number and does it have digital control or mechanical?

 

[EBSTINGRAY]

Pressure should be 43 psi at 1800 rpm
Being an EC motor, do you have the engine serial number and does it have digital control or mechanical?

Hi, Thanks for your swift reply. I will have the fuel pressure measured again and see if it is that, but my engine doesn't reach 1800 rpm with the issue I have:/.

The serial#: 2a452840.

I have uploaded a video of the engine running where you can hear the pulsing.

When you refer to the digital or mechanical control do you mean if it has computer? It does have a engine control computer and I can hook up Smartcraft device and see the engine on my Vesselview app.

Thanks, I appreciate any help I can get.

 

[alldodge]

Vids work best when using things like youtube and link back here by by using the camera link

 

[QBhoy]

Hi
How did you test the fuel quality. Not to doubt your mechanic, or you, but assuming this isn’t a merc or marine mechanic with diagnostics in hand to help ?

I’d run her off a remote tank to totally rule out the most common and odds on favourite source of such issues on such a new engine. The fuel supply from tank to engine.

 

[EBSTINGRAY]

Hi
How did you test the fuel quality. Not to doubt your mechanic, or you, but assuming this isn’t a merc or marine mechanic with diagnostics in hand to help ?

I’d run her off a remote tank to totally rule out the most common and odds on favourite source of such issues on such a new engine. The fuel supply from tank to engine.

Hi,
Ok try if this works.

I will try the fuel from a different source. We looked at the clearness of the fuel coming from the rail once we tapped it. It looked clean. The engine runs perfect idle too. It just doesn't properly rev up.
My mechanic is a marine veteran working with bigger boats normally, but not familiar with this engine in particular. We have tried many things like replace the ECM with a identical and it keeps doing the same. We replaced throttle position sensor, idle air sensor, and other parts.

 

[alldodge]

That sounds terrible, like gears and metallic type sound.
What happens when its reved up higher, like in throttle only mode?

Need to scan the motor for codes

 

[EBSTINGRAY]

It's not the gears. Maybe that is what it sounds like in the video. We scanned and there are no codes. It runs fault free but seems to have issues getting fuel to sustain the increased rpm. After I give more throttle it ultimately backfires in the exhaust. I will try a external fuel source and test the fuel pressure when it's running.
I will let you know. Thanks for looking into this.

 

[alldodge]

If a scanner is placed back on it, watch the TPS volts and IAC position