Marlin 300 fuel tank advice

[REBThunderroad]

To all Marlin owners! Any consensus on running down one fuel tank before the other? ie...run down the aux (aft) tank before the main (forward) tank or visa versa? Looking for the best fuel burn and ride on longer trips...

Thanks
Rob
2005 Grady White Marlin - F250's

 

[seasick]

To all Marlin owners! Any consensus on running down one fuel tank before the other? ie...run down the aux (aft) tank before the main (forward) tank or visa versa? Looking for the best fuel burn and ride on longer trips...

Thanks
Rob
2005 Grady White Marlin - F250's

You will get the best fuel mileage by having only the gas you will need for a trip plus a reserve. The more fuel you carry, the more weight and that affects performance.
Of course, that approach is often not workable for longer trips. The other most important factor for better gas mileage is a clean hull.

Bottom line is that the weight of the fuel in general is more of an issue than the distribution. Every extra 25 gallons of fuel is equivalent to carrying another 165 pound passenger
Also note that even if you get a tad better performance using one tank, you want to alternate tank usage so that fuel doesn't get stale. Switch tanks every now and then and add fresh fuel as needed

 

[g0tagrip]

On the long trips I have taken I have not noted getting better milage running a particular tank down first. What I have noted is that engine trim is very important so what I do is adjust engine trim to get the fuel flow as close as possible to what Grady White predicted is best L over D max (sorry aeronautical term) best long range cruise. For my boat it is 4100 RPM. Now if I am not going long to fish (with live bait in the well) but just cruising then close the seacock to the live well. I have noted that it does make a difference. In any case adjust RPM to 4100 and engine trim and check the fuel usage gage to get as close as possible to 20.6 gallons per hour. Should give you 1.3 to 1.4 miles per gallon. And I agree change tanks to keep fuel fresh. On our long trip to the Keys, I changed tanks every 75 gallons.

 

[Ozz043]

G-Day
I would tend to use the aux first, leaving 100L for safety margin. Having the fuel midships in the main seems to make more sense, better for stability and better for lift on plane.

I tend to run this way all the time, using the main to run around then add 100L to the aux every second or third refuel to refresh. I then use the aux till there's 100L left then swap over to the main again...keep the cycle going...

Any thoughts ?

 

[Tuna Man]

This time of year here in NJ we might go only about ten miles in a weekend to a local swimming spot and perhaps 250 miles the next weekend to one of the canyons for a fishing trip.

As the seas are not always as predicted, I have a strong tendency to keep the forward tank full and burn the aft tank first, always. This helps keep the bow down and the boat runs smoother as a result. On the other hand, if all we did were trips in the bay or near shore, I would prefer as little fuel on board as practical.

I would urge you to try to keep the fuel fresh. Not really a problem for us lately as we've been heading offshore at least every other weekend.

 

[LastChance]

When I stop for fuel, I top up both tanks. But I usually stop at preferred marinas where I can get commercial prices on fuel. Some of the docks (which I avoid) in the boonies where we cruise charge $1.60 per liter for gas.

 

[NO REGRETS]

Sorry for the intrusion, Not a Marlin owner. I run each tank at the same time I run my port off one and the starboard off the other. In my mind that keeps fuel fresher and the idea that both engines are independent if fuel were to be an issue.
I normally will keep 1/2 to 5/8 at the most. I don't do long trips so don't want the extra weight of the 300 gallons possible. When I did long trips I would operate the same way, except I would start full of course. :sorry

 

[jip40]

Again, I'm not a Marlin owner but close enough.

I'm assuming the Marlin is setup like the 330 where the generator (if there is one) runs off the Aux tank (150 gal) burning approx. one gallon per hour. The Main tank on my boat holds 200 gallons. I have the Garmin GFS10 fuel computers and consider a full load of fuel 300 gallons. That gives me a 50 gallon buffer, which covers the generator burn & a bit extra to get to a fuel dock.

I like to keep the fuel moving and not sitting so I tend to run one engine off the Aux tank a bit and then run both off the Main. I tend to top off the fuel at the beginning of a trip not at the end.

 

[devildogdad]

I have a 2012 Marlin and I run with both tanks open. My generator has it's own separate diesel tank . I have never had a problem and this way I when I do fill up I get fresh fuel in each tank. Keep in mind that when I do go off shore off of Tampa Bay, I go out 65 miles and back so I use a lot of fuel.

 

[REBThunderroad]

thanks everyone