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92 series Detroit Diesels

Discussion in 'Engines' started by Oscarvan, Dec 2, 2015.

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  1. Capt Ralph

    Capt Ralph Senior Member

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    Bring your foam ear plugs to save you from the 1000rpm howl.
  2. Capt J

    Capt J Senior Member

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    Figure 2.75 GPNM with 8v92's and 2.5 gpnm with 8v71's at $3 per gallon, divided by mileage , figure 900nm's just guessing on the mileage, including all of the in and outs of inlets. $7425/2475 gallons with 8v92's, and $6750/2250gallons. But this should be fairly close, if you're running the ocean and at cruise (except for ICW Norfolk to Beaufort,NC).

    Like everyone else said, keeping RPM's at 1000 rpms (about 8gph for both 71's, and 10 gph for both 92's) or net you a lot better fuel burn per mile. BUT, this time of the year I'd get South as quick as possible. Then you have to figure all of the additional in and out mileage you're adding (going in and out of inlets, just to get to the sea buoy's to go South) if just doing 8-9 knots and days......additional marina fees, Captain (if you hire one), dinners out, additional days you're weathered in this time of year coming up, and on and on. On a boat this size, you really don't save a ton more on a long trip like this by running slow when you factor in your time and additional expenses.
    Last edited: Sep 7, 2016
  3. RER

    RER Senior Member

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    How fast are you running? He asked about the most efficient speed.
  4. Capt J

    Capt J Senior Member

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    Like it says in what you quoted. Cruise. He asked the most efficient speed after I typed that. The most efficient speed would be dead idle, in gear, but that wouldn't be logical, comfortable, or good for the motors. Read my later post regarding additional days, additional weather days, marina expenses..... on a 46' it's not logical to do a long trip like this at hull speed, unless you've got the crew and weather to do long pokes (overnight legs), which I just did earlier in the week by going from Fernandina Beach 350NM to Fort Lauderdale non stop on a 45' lobster boat. It only cruised at 10 knots. It took about 2 hours from the marina just to the sea buoy in Fernandina beach at 10 knots..... Same with at Hilton head....so you're wasting 2 hours out the inlet, 2 hours back into an inlet in a lot of places.....to only do a maximum of 7-8 hours South. When you add all of the extra mileage, days and hours, you're creating by going in and out over twice as many inlets because you're doing 9 knots everyday, dockage, etc. what are you really saving? That $3k in fuel gets eaten up really quick with an additional $1000 in dockage, food, and extra days. And, now you're getting into Fall where the chance of not having a weather window and getting stuck at a dock somewhere is even greater. AND, if he needs to ask this question, he needs to hire a Captain at $350-400 per day to help him get it to Myrtle Beach! AND, if you find cheaper fuel the savings are even less of a difference. I just paid $2.50 gallon in Hilton Head and $2.25 in Fernandina Beach at marina fuel docks with no discount (pump price).....What are the savings then? I just quoted $3 a gallon because in the NE fuel tends to be a little more.
    Last edited: Sep 7, 2016