Fuel consumption 36 ET turbo vs non turbo

[alwsail]

I am looking at two 36 ET's, one with the 420 Cat. and the other with the 450 Cummins. I plan on using this boat as a true trawler except to speed up once in awhile to clean out the engine. So I plan on cruising at 1400rpm doing 7.3 knots at about 4 gph according to the great fuel log Mariner did. My question, is there an advantage to the turbo for fuel consumption or is it going to be a problem at 7.3 knot over a long period.
Thanks
Al

[joreyn]

Al, at 1400 rpm the turbo is not a factor. With my twin cats, the turbo kicks in around 2000, and is most noticeable above 2200.

I mostly cruise the way you describe. Every so often I find myself in a situation where I need the speed. The turbo makes a big difference when that happens.

[Mariner]

It's pretty important that you get the RPM up more than "once in a while to clean out the engine". Any diesel engine (especially one with a turbo) should be run at near wide-open at least a few minutes every time you turn it on, preferably near the end of your voyage, but with enough time to cool off before shut-down. That isn't always possible, due to no-wake zones and whatnot, but you should make an effort whenever possible. The turbo actually improves fuel efficiency at high RPM, but will hurt it at idle (compared to an engine without a turbo). But, the 3126B is a pretty fuel-efficient engine at displacement speeds. My fuel consumption graph for Nordvika is floating around the board. That is based on some pretty detailed monitoring, and has held true over time.

[arcticspud]

I don't know about running it at WOT. I do plan on running mine at 80% power for the last 20-30 minutes of the day to clear out the carbon and heat up the engine and the oil to cook of any water or other contaminates.

I have the 6BTA (270s) and they are rated to run at WOT for only 1 hour out of every 8 hours. That tells me Cummins doesn't want them at WOT unless I am outrunning the Canadian Navy or pirates in the Salish Sea (insert sarcasm) .

[RobS]

It's good to run them up to WOT periodically to verify your hitting your WOT target rpm and all is well.