2004 420 DA questions

BVasily

BVasily

Member
Jan 5, 2007
66
Kingston, Ontario
Boat Info
420 DA
Engines
Cummins 450C
Has anyone calculated optimum cruising RPM based on Cat 8.3 power curve and hull design?
Continually need to recalibrate auto pilot each restart of engines? Any advice?
 
I do not know the answer but I will offer this.....Mine has Cummins 480 and the tachs at 2400 puts mine at 29.5 - 30.0 SOG. When I look at the smart craft it shows a burn of 40.5 gal/hr. It gets considerably worse burn if you take it wide open. I usually cruise at 2200 and I think it is not planing as efficiently as it does at 2400. Fresh water at approx 1100 ft altitude if anyone cares.
 
I'm a little confused by the question. You have Cummins engines but are asking for optimum cruising RPM based on a Cat 8.3 power curve?
 
ASH said:
I do not know the answer but I will offer this.....Mine has Cummins 480 and the tachs at 2400 puts mine at 29.5 - 30.0 SOG. When I look at the smart craft it shows a burn of 40.5 gal/hr. It gets considerably worse burn if you take it wide open. I usually cruise at 2200 and I think it is not planing as efficiently as it does at 2400. Fresh water at approx 1100 ft altitude if anyone cares.
Click to expand...

If you're burning 40.5 GPH at 2400 you are OVERPROPPED. The 480CE is only rated to burn 19GPH/Side (38 GPH Total). Common wisdom on these engines is to cruise at 2200 burning no more than 13.6GPH (27.2GPH). If you're going to cruise at 2400, ensure you burn no more than 17.5GPH (35 GPH Total). It sounds like your props need to be dropped in pitch by atleast 2".

The 480CE is particularly sensitive to overload, it usually results in a dropped #6 exhaust valve or seat. This usually takes out a piston, cylinder liner and the turbo.
 
Jmwarren said:
If you're burning 40.5 GPH at 2400 you are OVERPROPPED. The 480CE is only rated to burn 19GPH/Side (38 GPH Total). Common wisdom on these engines is to cruise at 2200 burning no more than 13.6GPH (27.2GPH). If you're going to cruise at 2400, ensure you burn no more than 17.5GPH (35 GPH Total). It sounds like your props need to be dropped in pitch by atleast 2".

The 480CE is particularly sensitive to overload, it usually results in a dropped #6 exhaust valve or seat. This usually takes out a piston, cylinder liner and the turbo.
Click to expand...

Tony at SB-MAR recommends you prop a 480CE the same as a 450C.
 
Jmwarren said:
If you're burning 40.5 GPH at 2400 you are OVERPROPPED. The 480CE is only rated to burn 19GPH/Side (38 GPH Total). Common wisdom on these engines is to cruise at 2200 burning no more than 13.6GPH (27.2GPH). If you're going to cruise at 2400, ensure you burn no more than 17.5GPH (35 GPH Total). It sounds like your props need to be dropped in pitch by atleast 2".

The 480CE is particularly sensitive to overload, it usually results in a dropped #6 exhaust valve or seat. This usually takes out a piston, cylinder liner and the turbo.
Click to expand...


I need to do some more looking....Could it be possible that on my 2005 it could be different. The fuel delivery system is a hybrid of mechanical and electronic.....I think it may have been the first year for that set up. I would also think that burning a little fat at 40.5 would be better than burning a little lean.

The good news for me is I am never going very far or for very long on this inland lake.
 
Lean/Rich is not the same on diesel.

A diesel will burn as much fuel as it can with the proper amounts of air. It can burn so much it can put out WAY more horsepower than the components its built with can take.

While you can prop as Cummins specifies for the 480CE, in the long run the engine wasn't built for that abuse long term. It will run fine until it doesnt, and when it doesnt its huge dollars to fix or will need a replacement. If you prop like the previous generation (the 450C) it will run for thousands of hours.

The best money you can spend right now is an account for boat diesel, do as much reading as you can in the Cummins forum and then ask questions. You will get real answers from techs who live and breath Cummins and have ZERO financial gain from helping you.

Bottom line is for any Cummins engine you want your fuel burn UNDER the rated burn from the Cummins spec sheet, and for some specific engines (the 480CE is a prime example) you want it WAY under the specs (the best reference being the 450C specs).

I think the 480 CE was only produced in 2004 and 2005, the predecessor was the 450C which is full mechanical, the 480CE is mechanical except the fuel system is electronic, almost all other components were from the 450C.

In 2006 the QSC 500 was released and is major evolution in the C series, its fully electronic.
 
Great explanation. My homework assignment for the winter is to pay for a boat diesel account and read up on my Cummins engines.
 
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