Fuel usage

[Capstan]

Anyone have any burn rates for a pair of 6-354's in the Gulfstar 43?
Would be interested to see how mine compares.

Capstan

 

[riverfrontauthor]

Diesel burn

I have a 73 Gulfstar 43 with twin Perkins 135s. Running one screw at 1500 I'll get 6-8 kts and burn 3.5 gph.
HOWEVER, running two screws, each at 1500, I'll get 8-10 kts and burn 2.5 gph.
Yes, I burn less diesel on two screws than I do one...
I gave up trying to figure out torque curves and angle of the rudders and just accept that Lucky wants to run on two screws

 

[Lobstah]

So you're getting 4kts out of 1 to 1.25 gal of fuel... sounds pretty good.

 

[Capstan]

I have a 73 Gulfstar 43 with twin Perkins 135s. Running one screw at 1500 I'll get 6-8 kts and burn 3.5 gph.
HOWEVER, running two screws, each at 1500, I'll get 8-10 kts and burn 2.5 gph.
Yes, I burn less diesel on two screws than I do one...
I gave up trying to figure out torque curves and angle of the rudders and just accept that Lucky wants to run on two screws

Sorry it's been a while but:
When I took the boat to Florida. Very rough conditions. 12' + in the Gulf Stream but the worst was from New providence to Chubb 4' to 8' 3 points off the Stbd bow. Wet wet wet
Anyway the fuel usage for 24hours (this was over a 3 day cruise. Roughly 8 hrs running a day) came out to approx. 180g. (dirty Bum and props)
We were running hard. The engines did not miss a beat. Considering the boat probably hasn't done anything like that in the last 15 years. It was impressive.
In Lauderdale I had the Fuel pumps professionally overhauled. Props and bottom done.
On the run back conditions were a lot smoother to say the least and the fuel burn:
running at 1,600 for most 2/3 of the way and 1,800 for the other 1/3
Approx. 83g
So that is pretty well spot on what you are getting.
Very happy indeed!

 

[mkh8911]

Capstan,
I'm buying a 1973 Gulfstar 43 MKI and was wondering if you know for certain the capacity of the fuel tank? I've heard 200 and 300 gallons. Just wondering if you knew for sure. Prior owner of my boat says it get 2.2 GPH both engines at 1800 rpm (9 Knots) and genny running.
Thanks

 

[Gmarr]

If you can get a clean measurement of the tanks to determine approximate square inches, you can narrow that down. 231 cubic inches - 1 gal US. Let's hope for rectangular tanks!

 

[BandB]

Capstan,
I'm buying a 1973 Gulfstar 43 MKI and was wondering if you know for certain the capacity of the fuel tank? I've heard 200 and 300 gallons. Just wondering if you knew for sure. Prior owner of my boat says it get 2.2 GPH both engines at 1800 rpm (9 Knots) and genny running.
Thanks

You can't go by what anyone says. You have a couple of ways of approximating or measuring depending on how precise you want to get. One is to measure the physical dimensions. Another is to empty into some other tank or system and see what it takes to fill it. You can't be sure what was initially put in the boat and, even if you were, it may well no longer be the original tank.

For approximation you might use the guages and sight glasses if there are any and get it to half empty/full and that would probably let you know if it's closer to 200 or 300. You have another issue too and that is usable capacity based on pickup location and type and based on condition of tank and any issues inside the tank, such as debris or sludge or water, all which would become issues if you tried to use it all. I know someone who recently made a purchase in your situation and his solution was to have a fuel company come polish his fuel and clean the tank and at the same time tell him exactly how much fuel it took to fill the tank. It was an odd number but actually greater than the stated capacity as apparently the builder had been conservative in stating the capacity. Some are and will call a 312 gallon tank 300, but then others work on the "close enough" principle and call 285 gallons 300.

 

[rwidman]

Most fuel tanks will have a label on them stating the capacity. That's one way of knowing.


Unless you have a fuel management system, it's pretty hard to know your accurate fuel burn unless you keep records over a long period. It's really hard to fill your tanks to the same level each time you fuel.


Speed makes all the difference in the world, especially once you exceed "hull speed". Jus a knot or two can double your fuel burn.

 

[sunchaser]

Let's hope for rectangular tanks!

Uh uh. Lets hope for tanks that conform to the hull sides thus optimizing volume drawn vs dead bottom space. Measure the tank's volume when fueling by marking a stick or sight rube at various gallons when filling from empty to full.

 

[Gulfstar 36]

The tank on my 36' MrkII trawler conform to the hull as demonstrated in these sounding measurements.

235 topped
225 30”
200 29”
150 25”
100 22”
50 16”

Uh uh. Lets hope for tanks that conform to the hull sides thus optimizing volume drawn vs dead bottom space. Measure the tank's volume when fueling by marking a stick or sight rube at various gallons when filling from empty to full.

 

[Capstan]

Capstan,
I'm buying a 1973 Gulfstar 43 MKI and was wondering if you know for certain the capacity of the fuel tank? I've heard 200 and 300 gallons. Just wondering if you knew for sure. Prior owner of my boat says it get 2.2 GPH both engines at 1800 rpm (9 Knots) and genny running.
Thanks

Think I posted on your other thread.
300g but no dipstick.

 

[Capt.Bill11]

Most fuel tanks will have a label on them stating the capacity. That's one way of knowing.

I wish that was true.