480ce fuel burn difference between engines

[Matt G]

2005 Sea Ray 420. Getting a fuel burn of around 14.5 gallons at 2200 on one side and 13.7 on the other. I also noticed the side with the higher burn rate runs a coolant temp of 165 vs the other side at 158. What can I check to see if one is too much or one is not burning enough fuel. Motors are 480ce. Just purchased the boat so upon testing this is what I found. Thanks. 

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[Matt G]

The guy i bought the boat from did that last year. He bought used the boat 4 years and that was the last time the coolers were serviced. I am going to do all the coolers in September. I am more concerned with the fuel burn difference. 

[Patrick]

Before you tear down the after coolers and heat exchangers, try flushing the system with Barnacle Buster.

It evened out both of my engine temperatures and lowered the high one. 

Get a 5 gallon bucket for each engine with the Sea Flush adapter for your strainer. 

The stuff works and don’t worry about the Zincs. It only attacks organic material. Doesn’t nothing to zincs.

[Ray Isaac]

Matt,

Just curious, on a related note how are you getting the Cummins data to the RayMarine display? It was my understanding that there was not an interface between Cummins and RayMarine?

Thanks.

Ray

[Dave Carlson]

I had the same boat and actually had a Cummins tech hook up the scanner to see about the difference and was told Cummins allows for a 5% variation. He also said to be less anal!

I do recommend you do a fuel burn chart as described numerous times on this site, When I was dialing in my 420 I found I needed to reduce the pitch to almost 25 to get it within the 450 curve Tony recommends. This improved the performance in the rpm range where most sane people run their engines and reduced cruising fuel burn by 5-6 gph.

[Matt G]

Thanks for the insight. I knew the previous owner. He got this boat 4 years ago and he had the 1000 hour service done upon purchase. I saw the parts they replaced and 4 injectors were listed so I assumed they went over it well. He only used it less than 100 hours in the 4 years. I just did the impellers.  I am planning on going through the cooling system at the end of this season. He did do the props probably 3 years ago but I feel a little vibration.  Cutlass bearings did have some play. The prop pitch is 27. 

[Steve Lewis]

MG,

There will always be differences between the engines.  they will never run exactly the same.  I have 480CE’s in a 460 Sundancer, cruise on plane at 2200 – 2220 and I find my coolant temps the same as yours.  Port engine runs 159 and Strbd runs 165.  That is well within the specification and could be explained by minor differences in load from engine to engine or manufacturing tolerances, or any number of things that are “normal operating conditions”……..  

Personally, I would not worry much about the differences.  I look for my baseline on my boat and then monitor for changes in that baseline.  If there are changes, then I go hunting for issues.  I would spend a season and get used to how it runs.  Since you have individual engine data read outs I would make a chart of RPM, Fuel Burn and vessel speed and chart it.  Compare that to the diamond 450 perf chart and see if you need prop mods.  Your 1 engine is pretty much spot on and the other is a little over.  I suspect mine is the same even though we had the props modified twice to get the totals down.  I am running 28-29gph at 2220 with “Our Full Load”

When you bought the boat did you have the cooling circuit serviced?  You might look at having the props balanced over winter layup as there might be a difference there.  Cutlass bearings?  all sorts of things that can account for the differences.  

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