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Hey guys just want to confirm I am doing my math correct and have a good rule of thumb.

I've always been told that 2/3 of your capacity should be used to calculate your run to and from. In another way 1/3 for the trip out 1/3 for the trip back and a 1/3 for trolling, idle while drifting and reserve.

Is that correct?

Going under the assumption that I have 185 gallon fuel capacity and my 454 get about .75 mpg. This gives me a range of 138 miles total. Divide that by 3 and I can safely travel about 46 miles from my home port.

Being conservative and including my trip from the dock to the inlet I can venture about 30 miles offshore?

Make sense?

Peter you can probably go a little further if you take the babylon cut to the state chanel. you have to idle down the state chanel ,so save on gas. and always it depends on sea conditions...Russ

Peter,

I would reccomend 10% rule here. if you have 185 gallon tank assume that you can safely burn about about 165 gallons or so. Remeber your pick ups may not get the last bit of fuel while pitching and rolling. I think you would find that 60 miles one way would not be unreasonable depeding on how much trolling you do.

When I had 454's, 60 miles out was pushing it, and I have a 231 gallon tank. I usually averaged .70 mpg.

120 miles at 18 knots and 6 hours trolling was right at 190 - 200 gallons, depending on conditions. I always brought 30 gallons in jugs.

Based on what everyone is saying 30-40 seems to be a safe bet until I do it enough to really get a good idea of what I am burning per trip.

I'm doing a similar math exercise right now. I've got a crossing from Lake Worth Inlet to Spanish Cay in the Bahamas coming up. I have used Garmin's HomePort software to track the route. 133 miles total. I have a 231 gallon tank. If I estimate a 22 gph burn rate with approxmiately 7 hours of run time, I'll burn 154 gallons total. With 10% unusable in the tank, this leaves me 53 gallons reserve. (The speed above is agressive and will more than likely drop back unless we have completely glassy conditions, which should only improve my gph burned).

The big question is will my burn rate be more than 22gph, or should I estimate something higher to be conservative.

I'm running 325hp, 427 Mercruisers, 3 blade 17x20 original props.

First time I've used the Garmin HomePort software, pretty cool tool. I can chart the entire trip with waypoints and a boat profile including gph, cruising speed, etc. and the software allows me to create a route and it spits out a nice chart with times, fuel burned, etc. I could slap up a graphic if anyone is interested.

I guess it depends at what rpm your cruising at. When I had 454's in my 33, I would cruise them at 3150-3200rpms (18-19 knots). By the flo-scans, that was 30-32 gph. I think 22gph is on the low side for big blocks, but I'm not familar with Fords.

Steve,
Your calulations are about right, I would bring an extra 50 gallons in a bladder, the gas prices here are going to be cheaper than in the Bahamas. You also can use the bladder after it's washed out to catch rain water for washing down the boat, I don't know what the cost of water is in the Islands, but when I was in the Virgin Islands it was expensive just to wash the boat down after a fishing trip. Good luck on the crossing.
Pete

Steve,

Without FloScans its tought to tell without time and stats and a bunch of fill ups but heres something to do but your running out of time.

Fill the tank to max.

Run the boat 5 - 6 hours at steady cruise. Take note of you milage after fillup. Go back after run and fill up again taking note of the gallons it took to fill backup and that will give you a general idea of what you burn based on milage or you can do it with time by keeping track of the hours.

Now if your loading the boat heavy to take supplies over, your burns gonna change and the run won't be quite accurate.

Pete/Bruce,
Thank you for your advice. You guys are the pros.
An extra 50 gals will give me confidence to make it to Spanish Cay.
Gas is $6.50 right now out there. I never thought I'd see that number.
And yeah, I will be loaded up, the garage is accumulating stuff to take over that would normally go on Tropical Shipping.
I'd rather not swing into Fox Town for gas, which is just prior to Spanish....and I heard West End has Ethanol in their fuel, so I'm skipping West End as a port of entry. I called West End to check the Ethanol in the fuel and the lady said they did have Ethanol. Maybe she just said YES and thought that was an advantage! Spanish Cay has the best Customs and a nice marina and some clean rooms/restaurant/bar...so that's the desination...I just need to make sure I can make it 130-140 miles on my 231 gallon tank.

Pete, any suggestions on the bladder? I may just purchase a large portable plastic tank w/wheels gas tank I could use on the dock later on. If a bladder is cheap, I'll go that route and not care about after use.

I plan to dock up at Sailfish Marina June 10th fuel up the night before and depart very early June 11th, approx 6am. If we have smooth crossing we should be on the bank very early before 9am, where we'll dive heads along the way to Spanish making it to the marina before they close for the night.

Here's the HomePort graphic with the Fuel Tab info.

sorry, uploaded the trip view,....here's the fuel view.

Pete, Depending on pickup location, Ive always been told 10% you cant get out of the tank...trolling speed always uses next to nothing, my buddy has run 165+ miles out one way and knows exactly how far he has to troll to be on the safe side...that being said on he way in, we HAD to stop at Menemsha, idling in the harbor I poured 5 in the stbd tank, two seconds later the port quits...my ride has 300 gallons no bladders...230 main 35 each saddle...experience learner...BH

Most we ever used on a trip from Barnegat Inlet to the tip of the hudson on the east wall was 210 gallons carrying an extra 50. Run out, troll all day, lay up overnight, troll starting in the morning, work our way in for two hours pick up and run. Never pushed her running out, so figure about 4 and half hours running going out, and then about 31/2 running home after working inshore a ways. Troll time about 12 to 15 hours.

Steve
If you can't find a reasonable priced bladder get a couple of plastic drums and a hand crank pump, I've done that with 3 of the 45 gallon plastic barrels on a run from Block to Cape Henry on a 46 Bertram awhile back, quite a while back now that I realize it (30 years ago). Just remimber youv'e got the stream running North, your offset from the stream, windage and weight will have a lot to do with your burn. When your loading the boat try and keep most of the weight around the back of the engine boxes, not at the transom. Have a good trip.
Pete