Can't Get Revs Above 700 RPM

[rschute]

Hi All, Upon launching my boat, I'm able to start my Volvo Penta 2002 engine but I can't get the revs up beyond 700rpm with full throttle.

Fuel appears to be getting everywhere it is supposed to get to and I had the engine running for 45+ minutes but only at low RPM and on 2 occasions it went to about 2000RPM but quickly settled down to 700RPM.

A few things to note:

- I observed a good healthy stream of fuel coming from the bleed screw, the injectors and injector pumps when the nuts were cracked open.
- The lever attached to the fuel regulation system is moving the full range when the throttle is in idle to it's maximum throttle position.
- Fresh diesel is being run directly to the lift pump.
- Both injectors were replaced 2 years ago.
- Primary and Secondary fuel filters are new
- The engine sounds okay at 700rpm

Does anyone have any ideas on why I can't get beyond 700 under full throttle?

[Mrkva]

Check the exhaust mixing elbow, it might be clogged inside reducing exhaust gas flow.

[rschute]

If it was blocked, would that possibly account for no increase or very little increase in RPM? I have decent water flow coming out externally through the exaust.

[Mrkva]

It might, because higher RPM means higher exhaust flow, which can get restricted by exhaust blockage.

[SY Harmony]

Are you getting any smoking?

[S/V Illusion]

Symptoms certainly sounds like a mixing elbow problem.

[MicHughV]

The engine is telling you it's time to go to pasture...

[skipperpete]

I just had a similar problem with a Yanmar 3GM, no rpm response for well over half of the lever travel and finally she picks up . Not resolved yet BUT the entire problem vanishes with the alternator belt removed ( currently awaiting a new alternator)
So my suggestion is to slack off the alternator belt or remove it for a brief test. I doubt that the circulating pump would be a culprit given that you achieved 2000 rpm on 2 occasions...... this would not be the case with a seized coolant pump but sounds about right for a rogue alternator/regulator.