Cruising RPM and avg. Distance

K

KenT1

New Member
May 30, 2011
19
California
Boat Info
1992 Sea Ray 370 DA
Engines
454's
New SR owner here. Ok well not new, but new to me..I have just purchased a 92 SR 370 Sundancer; and I am itching to get her out and about. But I have a few questions and hope you all can help.

My boat has twin 454's (7.4) and I will assume stock prop's on her. I have no idea what the most efficient cruising RPM is?? Or distance I can cover on the combined 270 gallons of liquid gold (I mean gas) :huh:

I live in Northern California (boat is on the delta right now) and wish to make semi regular trips to Monterey CA.

Any help would be great.
 
Another 370 DA owner can chime in on what the book says but I would recommend installing a GPS/chartplotter with the capability to interface with fuel flow meters. That way you can instantly calculate MPG and range down to the gnats a$$ for any given RPM.
 
Do a search, we have 370 dedicated thread with lots of info.
 
pchansen said:
Another 370 DA owner can chime in on what the book says but I would recommend installing a GPS/chartplotter with the capability to interface with fuel flow meters. That way you can instantly calculate MPG and range down to the gnats a$$ for any given RPM.
Click to expand...

I spent several years keeping logs and comparing data to optimize my cruising style. I eventually found the sweet spots, but as PCHansen described, what took me thousands of gallons of fuel to determine back then, now shows on my GPS plotter instantly. (and much, much more)
 
RollerCoastr said:
I spent several years keeping logs and comparing data to optimize my cruising style. I eventually found the sweet spots, but as PCHansen described, what took me thousands of gallons of fuel to determine back then, now shows on my GPS plotter instantly. (and much, much more)
Click to expand...


What make of chart plotter, and do you have inline fuel flow monitors?
 
I have a Garmin plotter talking to Garmin's GFS-10 inline meters on a NMEA2000 network. I'm planning to create a thread about the installation soon, but the short of it is that I wish I had done it years ago.
 
You don't need no stinkin' GPS hooked up to anything. Just push the throttles to the firewall and get there!

Oh, by the way, Exxon will love you!
 
We use the following
One US gallon per knot at 1200 to 1400 RPM= speed 5.5 to 6.5 knots
One and a half gallons per knot at 1800 to 2000RPM= speed 8 to 9 knots
Two point eight gallons per knot at 3800 RPM= speed 17 knots
 
Thank you, this seems to be a simple way guesstimation for fuel burn. And much cheaper than a gps (for now) I would be interested in the gps set up RollerCoaster speaks of. But not till end of year. $trapped
 
Here is my guess for fuel cost to Monterey (one way) from not too far up the Delta. It would be just about a boat load of money.
 
Ken... having your same boat with same engines you WILL burn 30 gph at 3000-3150 rpm. (assuming a decent state of tune and depending on weight) After that, your secondaries will start to kick in and you will hear the engine tone change to a higher pitch. That being said, you dont want to cruise in that range since your numbers go stratospheric and your wallet gets emptied really fast. I like to cruise at 3050-ish at 21-23 mph using a little trim tab. The bow rides a little high when you are fueled up fully, nothing a bit more tab wont correct.... Your props are likely 17x16 (3 blade). Mine are. Hope that helps you a bit. We do have a 350/370 thread you can post on as others have said...
 
Mark taught me that when I got this boat. "Stay out of the secondaries!" All 454s (naturally aspirated) have the same consumption curve. At each RPM, when loaded properly, they will all burn the same amount of fuel. Weight, wind resistance, dirty bottom will affect your speed and MPG, but not your GPH.

Mark is right on the money with his numbers and recommendation for your "sweet spot."
 
When you get the cash for the GPS/GFS-10 setup, do it. I wish I had done it sooner, even on my little Chris-Craft.
 
Thanks guy's, all this information helped. I took the boat out this weekend. with full fuel tanks, fresh water and loaded fair with food and friends. I tried to run the boat on avg. @ 3000 RPM (and note my run times) for the bulk of the day. At days end I went and purchased some more liquid gold... I was supprised to find that I was burning about 28 GPH. Which means I need to check the tide's and wind a bit closer for a longer haul to Monterey.
Has any of you some information on the run to Monterey from SF Bay? Any pointers / hints??
 
Sounds about right. I'll venture a guess that at 3000rpm and that cargo, you were making about 18mph (?)
 
I used to have the same power in a 1995 370da and I can tell where the "sweet spot" definately is not. I forget the exact RPM, but it looks like you are gaining about a knot and a half of speed with only about a 100 or so increase in RPM. In fact, this is the point where the other 2 barrels of your 4 barrel carb open up and your mpg really goes in the toilet. I'm very glad that a friend clued me in early on when I told him about my boats "sweet spot". Flow meters sound like a good idea to me too.
 
Last edited:
You must log in or register to reply here.

Forum statistics

Threads
113,193
Messages
1,428,284
Members
61,104
Latest member
Three Amigos
Back
Top