What say you? Planing or creeping when you're almost out of gas?

[Expidia]

Situation arose yesterday on way back to dock. Started trip with a full 6.5 gallon tank but it ran dry with about 5 miles left to go.
Never had that happen on this run I've made back and forth many times over the years.

I think it happened because it was 96 degrees out and I was cruising (around 25 mph) which was faster than usually as we needed the cooling breeze of the higher speed. I usually cruise around 18 mph just fast enough to keep it on plane.

I have no gas gauge on this plastic tank, but I never needed it because I always keep a spare 2 gallon tank in a bow locker figuring 2 gal will get me just about anywhere I need with my 40 hp O/B like when you pull up to a marina pump when your on fumes at 5pm and they are closed
I usually travel no more than 1/3 of a tanks worth (apprx 2 gal) before heading back or stopping somewhere to top off. I figure I still have the 4 gal gal plus an extra .5 left of the 6.5 gal tank and I always have the 2 gal spare. A gauge would of course be nice but I've never found the ones built into a tank all that accurate. Either way, I've always figured the spare tank of gas will get me home, a faulty gauge won't.

So yesterday, the main tank ran dry 2/3 rds of the way back and I said no problem, pulled out the spare 2 gal tank and was surprised that it was only 1.4 gal and not full as gas exapnds with heat so I had left a little air space. I must have gotten it mixed up with a few other tanks I store full in my garage.

Poured it in and I had already used probably 1/2 a gallon up when I pulled into the Cold Springs boat club (a private club) and asked if there was a gas station I could walk to for some extra gas as I did not want to run out in the middle of the large bay I had to cross to get back to my trailer. One guy said the station more than a walk but he would be happy to drive me up there. An nice gentleman in a blue shirt and Joe, I think the dockmaster, had me back into an empty slip and as I walked into the parking lot a guy in a truck (Roger) pulled up to fill his boat and he offered to fill my 1.4 gal tank. He wouldn't even except any cash! What a great group of guys at that club! Kudos to the 3 guys that helped me out!

So my question for the forum is when one is running low on gas is it more fuel efficient to plug along at say 7 mph where the throttle is only forward ever so slightly or is it better to get the boat up on plane where the throtlle is half way down. Which was covering a lot more river at 18 mph but it probably would have not gotten me back to the dock with only 1/2 a gal left at that speed. I chose to plane on that 1.5 gal as I figured i was covering a lot more river (less to row to the dock) but I know I would have not made it all the way on my own without that other gal I got from the club.

Update: just checked the spare tanks in my garage. Yep, the one I put in the bow was the wrong one! I put the correct one now in the bow locker which I've used for past 5 seasons. It's 2.8 gal. That one would have taken me just about anywhere!

 

[Philster]

Re: What say you? Planing or creeping when you're almost out of gas?

Idle speed in gear.

 

[lakelover]

Re: What say you? Planing or creeping when you're almost out of gas?

I plan on carrying an extra gallon that would get me back home from anywhere on my lake. I would definitely go easy on the throttle, I've been surprised how the motor only sips gas that way. With a storm coming or something though, I'd take a little more of a chance. (Yup, it's a pretty small lake).

 

[64osby]

Re: What say you? Planing or creeping when you're almost out of gas?

Idle speed in gear.

+1 One the Merc 500 that I had, I had a 6 gal main tank, a 2.5 back up tank and a 1.5 gal gas can that was tucked under the splash well. Ran out of the 6.5 twice in 8 years, first time I only had the 1.5 gal back up. Then I added the 2.5 spare. Too much gas is always a better option.

I would try and find a way to add another tank or more small gas cans.

 

[acarter92]

Re: What say you? Planing or creeping when you're almost out of gas?

I would think that being on plane would be better, probably your slowest speed that your on plane. Although I've never tested this and I'm sure someone has a better answer.

I have a total of (3) 6 gal tanks, but two fit nicely under the splash well (one on either side). If we are going long distance I take three, although the third one has no "good" place to store it. Seems like the simplest thing to do would be to just buy another tank. I picked up 2 new ones on ebay when I bought my boat. I think I paid like $65 or $70 bucks for both new Moeller's shipped to my door. Then you never have to worry about it again.

Just my $0.02

Austin

 

[Expidia]

Re: What say you? Planing or creeping when you're almost out of gas?

Thanks for those responses. Idle speed would have been my first choice, but since its a river there is barge traffic. Cound not take a chance of it getting dark and I'm still out there. Shoreline is quite shallow and rocky at low tide which we were at. Luckily, I got that extra gallon which then I was all set.

Idle speed at 5 mph covering over 15-20 miles would have brought way into the dark!

I have a searchlight on board and a GPS combo so I could have followed the buoys back along the side of the channel. But if I ever get caught in a similar situation, I'll use idle speed. This is good to know. Unless someone chimes in with an opposite opinion.

I see some other responses now that say planing speed! That's what I had done, tapped it to just planing but I know without the extra gal at planing I would have been paddling in the middle of the bay at some point

 

[rivermouse]

Re: What say you? Planing or creeping when you're almost out of gas?

+1 One the Merc 500 that I had, I had a 6 gal main tank, a 2.5 back up tank and a 1.5 gal gas can that was tucked under the splash well. Ran out of the 6.5 twice in 8 years, first time I only had the 1.5 gal back up. Then I added the 2.5 spare. Too much gas is always a better option.

I would try and find a way to add another tank or more small gas cans.

having gas cans expanding and leaking fumes ALL OVER you boat is sorta dangerous. Cans inside of a locker leak fumes and then the fumes have no place to go... ONE LITTLE SPARK AND BOMMMMMMMMMMMM.

 

[Expidia]

Re: What say you? Planing or creeping when you're almost out of gas?

If your O/B has no issues with being in gear at idle speed (many of them tend to load up) then I'd say putt putting it back with no throttle. I had sort of the same issue on a weekend outting and others (brother) driving the boat and not watching the gas guage and when we were ready to leave it was below a 1/8 tank and we had a ten mile run to the dock. That boat had a 350 V-8 and I put it in gear and left the throttle alone and we made it back with gas to spare and I know that would not have been the case on plane with the load we had in it.

Note: We were fortunate that there was no wind and the water was calm so we made good headway at idle, I don't know if that would be true if the water was rougher.

Ya, the wind and waves could make a big difference for sure. Try paddling a 15 foot boat . If I did not get that extra gallon I was planing on anchoring in a cove (leaving my wife to watch the rig) and hitching hiking along a side road to a gas station rather than running out in the middle of the bay.

The front locker I store the plastic gas can in is really not a closed locker like my battery and anchor lockers. It's more of a square hole in the bow where I keep the bowline and I had installed a hailing horn, yet there is still plenty of room for the 2.8 gallon tank.
I just drained a little off the tank to allow for expansion before I stored it. Carrying to much extra gas onboard scares me. If that gas expands then its going to flow under the deck. Some twit with a cig hanging from his yap, jumps on my rig and bang, it'll look like the July 4th!
I looked at increasing the capacity of the 6.5 gal tank to 9 gal as the Lunds gas locker is bigger than 6.5 but I can't find one that's low enough. Custom is expensive and 9 gal along with my other gear in the back would dampen my hole shot somewhat. The 2.8 up in the bow balances it off. This gives me 9.3 total capacity.

 

[64osby]

Re: What say you? Planing or creeping when you're almost out of gas?

having gas cans expanding and leaking fumes ALL OVER you boat is sorta dangerous. Cans inside of a locker leak fumes and then the fumes have no place to go... ONE LITTLE SPARK AND BOMMMMMMMMMMMM.

RM - I use gas can as a general term, this is a plastic 1.5 gallon gas can with a cap and vent that is plugged. The other tanks vent as they should, and I've never gone boom.

 

[saxrulez]

Re: What say you? Planing or creeping when you're almost out of gas?

It can depend on the boat/engine combo, but here is an example of a 2 stroke and its mpg/gph. It got its best MPG(which is what is important if you're trying to cover the most ground with the least gas) at cruise.

http://www.yamaha-motor.com/assets/...hpmidport_rel_syl-1900dcadventurer-150txr.pdf

The only real way to know with your setup would be a fuel flow monitor of some type. You could also do some redneck math/experiments.

 

[saxrulez]

Re: What say you? Planing or creeping when you're almost out of gas?

It can depend on the boat/engine combo, but here is an example of a 2 stroke and its mpg/gph. It got its best MPG(which is what is important if you're trying to cover the most ground with the least gas) at cruise.

http://www.yamaha-motor.com/assets/...hpmidport_rel_syl-1900dcadventurer-150txr.pdf

The only real way to know with your setup would be a fuel flow monitor of some type. You could also do some redneck math/experiments.

Here is another example with the opposite being true.

http://www.nauticglobalgroup.com/test/HUR-FunDeckGS201-F115TXR.pdf

My hypothesis would be that 4 strokes get better mpg while idling and 2 strokes slightly better at cruise. Its just a guess though, so take it for what its worth.

 

[sstone]

Re: What say you? Planing or creeping when you're almost out of gas?

Completely unrelated set up, but my 5.0 mercruiser in a sea ray gets incredible mileage just past planing. There's much less water resistance/wetted area in that state, so the load on the engine less. From an engineering standpoint, there's an optimal point where the fuel consumption (somewhat linear increase with rpm), engine load (which will have an effect on fuel consumption, and mph combine for your most efficient speed. Do some redneck math/experimentation as suggested to find the best for your setup. That got way more long winded than I expected

 

[Texasmark]

Re: What say you? Planing or creeping when you're almost out of gas?

Many boat mfgrs publish performance data with their combinations (boat/engine factory assembled) and several engine mfgrs publish comparative data for their engine vs a competitor on the same boat. Looking at these curves and fuel efficiency, you will find that your best mpgs are just on plane. There is a big change (improvement) in the mpg curve at that point and as speed increases, the curve flattens out; efficiency gets worse.

So there is your answer and it's published numerous places.

Mark

 

[Expidia]

Re: What say you? Planing or creeping when you're almost out of gas?

Well, I see we went full circle. That's OK as if I run out of gas again and It's early enough I'll limp back on idle. If weather or darkeness is an issue I'll edge it just over planing speed.

Been boating probably 45 years and never thought about this type of gas saving question! Always carried the spare 2.8 gal, not the 1.25 which I put on board by error.

On another note, old age is moving in on me . . . gave my porta pottie a nice cleaning last night. I keep it at the bow of the boat. My Wife's favorite accessory Well, pulled up to the launch and only saw deck where the porta potty sat. Realized it was drying off very nicely on top of a plastic trash can in my garage

Needless to say my Wife was "pissed" no pun intended first time I ever forgot this accessory of comfort!

Oh, ya . . . went to take off the bow line after launching, stepped on the gunnel and the boat moved away from the dock and found myself instantly standing in 3 feet of water. Worst part was I never go near the water without my smartphone in a zip lock bag and then inside a Sealine waterproof bag (which was of course still on the back seat of my car).
Pulled the battery and left the phone on the dash in the sun all day. Got home pulled the cards out of warmed it up with a hairdryer. Now its in a canister of rice. Will switch on in the AM and see what I've got. Hope it works as even though I have insurance Verizon nails you for a $90 or 95 deductible! Almost canceled the insurance last week as the phones 2 years old. Trying to lower bill, but I said to myself . . . better wait till the end of boating season! At least I got one thing right lately!

Tonight, still limping around as I sprained rt hip a little when I went in. Popping Ibuprofins.

Update: 9AM following day. So far the warm air flow from a hairdryer on the $120 electronic car key and $600 Smart Phone (I paid $199 under contract) and into a bowl of rice overnight in a sealed container might have saved them so far. Both are .

Looks like the only thing that was damaged (besides my body) was my PRIDE

 

[CaptainKickback]

Re: What say you? Planing or creeping when you're almost out of gas?

Well, I see we went full circle. That's OK as if I run out of gas again and It's early enough I'll limp back on idle. If weather or darkeness is an issue I'll edge it just over planing speed.

Been boating probably 45 years and never thought about this type of gas saving question! Always carried the spare 2.8 gal, not the 1.25 which I put on board by error.

On another note, old age is moving in on me . . . gave my porta pottie a nice cleaning last night. I keep it at the bow of the boat. My Wife's favorite accessory Well, pulled up to the launch and only saw deck where the porta potty sat. Realized it was drying off very nicely on top of a plastic trash can in my garage

Needless to say my Wife was "pissed" no pun intended first time I ever forgot this accessory of comfort!

Oh, ya . . . went to take off the bow line after launching, stepped on the gunnel and the boat moved away from the dock and found myself instantly standing in 3 feet of water. Worst part was I never go near the water without my smartphone in a zip lock bag and then inside a Sealine waterproof bag (which was of course still on the back seat of my car).
Pulled the battery and left the phone on the dash in the sun all day. Got home pulled the cards out of warmed it up with a hairdryer. Now its in a canister of rice. Will switch on in the AM and see what I've got. Hope it works as even though I have insurance Verizon nails you for a $90 or 95 deductible! Almost canceled the insurance last week as the phones 2 years old. Trying to lower bill, but I said to myself . . . better wait till the end of boating season! At least I got one thing right lately!

Tonight, still limping around as I sprained rt hip a little when I went in. Popping Ibuprofins.

Can we add you to the "Docking Bloopers" video that's all over You Tube? lol

Sea ya...

 

[H20Rat]

Re: What say you? Planing or creeping when you're almost out of gas?

nobody asked yet, but OP said river... How much current? Some rivers have negligible, if any, current, and others are a couple mph. A couple MPH current will have a HUGE impact in the correct answer. If you are needing to go upriver, idling is going to be a very poor choice. The longer you are in the water, the further your effective distance you need to travel becomes. (ie, if you have to go 10 miles, and are idling at 5 mph indicated speed in a 2.5mph current, you are going to travel 20 miles, over the course of 4 hours. Traveling on plane at 20mph would put you home in a little over 30 minutes, with 11.2 miles total distance. For the typical boat we are talking about here, you are going to use far more fuel in 4 hours of 5 mph idling than a 30 minute 20 mph cruise.)

And of course, going downriver, best mileage is with the engine off...

 

[lakelover]

Re: What say you? Planing or creeping when you're almost out of gas?

Tonight, still limping around as I sprained rt hip a little when I went in. Popping Ibuprofins.

What a day on the water! Several times lately I've thought about cutting back on certain things to "realign my cash flow". Some I'm glad I did, some I'm glad I didn't. You just never know I guess. Love the porta-potty chapter .

 

[Texasmark]

Re: What say you? Planing or creeping when you're almost out of gas?

Unfortunately none of them say anything about leaving the engine at a dead idle.

Well I thought that is where the curve started. At dead idle you are doing 675 rpm if you adjusted your idle like my manual recommends on my engine, in the water in F gear. You are doing maybe one mph.

I have curves that I plotted on my boat and I am on plane at 18 mph and 3000 rpm. At 3100, just on plane I am at 20 mph. So a little arithmetic and I am turning 3100/675 = 4.6 times the rpm's and I am moving forward 20 times the distance.

Seems like apples and oranges to me and don't feed me the stuff that the engine efficiency is worse. Actually it is better as for one thing the exhaust is creating a vacuum due to the tru prop exhaust and since an engine is an air pump when you move the air through it easier, you don't spend as many BTUs making it happen. The BTUs are converted to actual hp that propels the boat.

Additionally the water that circulated in behind the boat at idle and all below plane speeds creates drag which isn't there on plane.

Mark

 

[Expidia]

Re: What say you? Planing or creeping when you're almost out of gas?

nobody asked yet, but OP said river... How much current? Some rivers have negligible, if any, current, and others are a couple mph. A couple MPH current will have a HUGE impact in the correct answer. If you are needing to go upriver, idling is going to be a very poor choice. The longer you are in the water, the further your effective distance you need to travel becomes. (ie, if you have to go 10 miles, and are idling at 5 mph indicated speed in a 2.5mph current, you are going to travel 20 miles, over the course of 4 hours. Traveling on plane at 20mph would put you home in a little over 30 minutes, with 11.2 miles total distance. For the typical boat we are talking about here, you are going to use far more fuel in 4 hours of 5 mph idling than a 30 minute 20 mph cruise.)

And of course, going downriver, best mileage is with the engine off...

Wow, nice observation. I never thought to even factor that in. You are correct as the Hudson River has a pretty fast southern current and I was heading against the current the whole trip back to Newburgh and my tow vehicle.


As you also pointed out about the tides too in that the Hudson has in some places of a 20-40 foot tidal (edit, the article was referring to places like the bay of fundi for that wide a tidal change, not the hudson river's 6-8 feet.height. I usually see around an 6- 8 foot change on my combo GPS with the sections I travel.

The waters are brackish from the mouth right up to Newburgh. Ya, 3 mph would not have cut it against the current, tides and any wind!
http://www.ecostudies.org/chp/Module1/1A2_tides_reading.pdf

 

[Bondo]

Re: What say you? Planing or creeping when you're almost out of gas?

As you also pointed out about the tides too in that the Hudson has in some places of a 20-40 foot tidal height change.

Hmmmmmm,..... No,... it Doesn't....

Bay of Fundy, Maybe,... The Hudson river, has Nowhere near that much change...