QSC 500 Cummings - can't get up to full speed

S

Sea Path 44

New Member
Mar 13, 2009
29
Wilmington, NC
Boat Info
44 Sedan Bridge 2006
Engines
QSC 500
44 Sedan Bridge 2006; QSC 500's Cummings with turbos. After the was boat sitting in the slip for two weeks, I went out and could not get either engine over 1800 RPM. I had the sync on. WOT is nromally 2650 RPM. I have 400 hours on the engines but they normaly purr. The Racors look clean. Any ideas?
 
Your props are crapped up.

Here in VA... 7 days is the max a boat can sit this time of year before the barnacles will take over the running gear.
 
shafts clean also?

Engine issues could be several... blocked fuel flow (on engine filter checked?). Is the turbo spinning up?

I'm always suspicious though of dirty bottoms this time of year.
 
The bottom was just painted 4 weeks ago and engines were re-aligned with new strut bearings installed. I'm goin to check those today with the mask on, but if the bearings were loose, I'd think that I'd probably hear bad noise. After the boat went into the water, it never ran faster....32 MPH verus 28 peak prior! Had the bottom scrubbed by diver two days ago in prep for the holiday weekend. Strange that both engines are dragging at 1800 or so RPM peak when WOT is 2650. I'll try the same today without the sync on to see if one of the engines is draging the other down with the sync. I'm thinking that it may be fuel filter clogged or turbo issues. Again, if both engines are dragging with the sync off, it may be electronic? Taking the sync off during today's outing will tell alot. Thanks.
 
No diesel expert here, but I know that when one engine has a problem- e.g. not able to produce the proper amount of power - it will force the other engine to struggle to compensate for it, and not be able to turn up to rated rpms. While you might think that neither engine can turn up, it's often one engine that has the problem and the other might otherwise operate normally.

You said they don't turn up under load, but have you checked to see if both engines turn up to max rated no-load rpms?
 
One engine slaves off the other. Your problem is likely on the controlling engine only. If the controlling engine is limited by anything, the slaved engine will only turn up the rpm's the controlling engine can turn, so they'll both be at 1800 if the controlling engine only turns up that many revolutions.

And, I'm betting on a secondary fuel filter being clogged up.
 
Tim,

I think bottom may not have been cleaned well or at all by diver. Have him clean again or use John B. He will get it done right. Also what Frank said is right, if you were on synch. If not on synch then check bottom. I have seen several boaters have this issue this time of the year and a dirty bottom was the culprit.
 
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Make sure ur cruise control is not on.... That will limit RPM at what ever it was last set too..

Bet thats it

Rob
 
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