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Can you get too big of a gas tank?

Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
Hi All, my first post. I'm referb'ing an M25 (Hurricane Michael special). The boat was pretty much flooded with fresh water. The existing 3 gallon tank was still connected to the Nissan 9.9 4 stroke.

Since I'm replacing pretty much everything and anything that can be replaced, I want to get a new gas tank. I currently have a 3 gallon tank which has some liquid in it (haven't even opened it to smell it).

I've looked at alternate tanks and the foot print of the 6 and 12 gallon tank is identical to the 3 gallon tank just taller.

Any thought on going with the 6 or 12 gallon? I was thinking with going larger because I have a 2000 watt Power inverter generator that I plan to use to run my portable AC unit an other electronics on weekend stays. I was thinking I would somehow connect/use the larger tank to run my generator.

Going with the 6 gallon, I'd be adding an additional 19 pounds to total weight when full and an additional 57 pounds if I go with the 12 gallon.

Thoughts?
 
Jul 7, 2004
5,837
Hunter 30T Cheney, KS
Size matters. Not just for the outboard, but for your "camper". It would fit your weekend plans and shouldn't affect your sailing I wouldn't think. Bring skinny crew!
 
Mar 26, 2011
2,371
Corsair F-24 MK I Deale, MD
Was the 3-gallon tank on deck, vs. installed in below decks? 6 or 12 sounds fine--that is the size I had on several boats in that range. But make sure the installation is SAFE. http://www.uscgboating.org/regulations/boatbuilders-handbook.php

I was sailing myltihulls and the tanks was under the bridgedeck, not in the hull. In the F-24 it is in a cockpit locker that drains only overboard through an open transom. No chance of fumes.
 
Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
Was the 3-gallon tank on deck, vs. installed in below decks? 6 or 12 sounds fine--that is the size I had on several boats in that range. But make sure the installation is SAFE. http://www.uscgboating.org/regulations/boatbuilders-handbook.php

I was sailing myltihulls and the tanks was under the bridgedeck, not in the hull. In the F-24 it is in a cockpit locker that drains only overboard through an open transom. No chance of fumes.
Yes, the existing 3 gallon tank is sitting on the deck, up against the transom. The 6 and 12 gallon would sit in the exact same place, it would just be taller.
 
Mar 26, 2011
2,371
Corsair F-24 MK I Deale, MD
Yes, the existing 3 gallon tank is sitting on the deck, up against the transom. The 6 and 12 gallon would sit in the exact same place, it would just be taller.
Then just make certain it will not snag sheets. That's a big deal.
 
Jan 31, 2009
5,252
Macgregor & Endeavour 26S and 37 Utah's Canyon Country

Joe

Jun 1, 2004
6,738
Catalina 27 Mission Bay, San Diego
My opinion is to go with a six gallon tank... then carry a couple of 5 gallon jerry cans... because... you can remove them and refill without taking the boat out of the water. It will leave your more options for refueling.
Also, I would invest in a long funnel. Cut the bottom at an angle, or drill a couple holes to allow you to steady the funnel on the tank's bottom when filling with the environmental spouts that require you to exert pressure to operate. (or get a transfer pump.
Another option is to get two portable six gallon units, and connect them with a wye valve to the fuel, bulb, filter portion of the hose.
 
Jun 2, 2004
2,867
Hunter 23.5 Fort Walton Yacht Club, Florida
The rules change in regard to placement, tie down and such when you go larger than a six gallon tank as it is no longer a "portable tank".

Additionally if you stick with a six gallon tank you have the option of grabbing the tank and walking down the dock to anywhere you want to get fuel that would not be an option with a 12 gallon tank.
A smaller tank allows you to keep fresh fuel more easily than does a larger one. I'd recommend a six gallon tank and get an additional one if you require more tankage. Oh, and remember two half empty cans are easier to carry than one full can.
 
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SG

Feb 11, 2017
1,455
J/Boat J/160 Annapolis
I don't know how much fuel you use; or if
  • You only use Ethanol Free gasoline; or,
  • If you treat the gas in your tank to mitigate the impact of the alcohol additives, etc.; or,
  • If you just ignore the issues.
I would suggest that using a larger tank could impact your outboard and the fuel system.

My view, is that decision might be informed by the convenience of the proper fuel availability, your range of uses of the fuel, how often you refuel, etc.

We have a some "dingy fuel" which I keep in a small jug for our 4hp, 2-stroke outboard that is over 30 years old. We through more fuel away than we use over a season. We keep additives in the fuel to mitigate the impact on our old 2-stroke, always burn all the fuel out of the carb each time at the end of the day, etc.

We also have a 24' center console powerboat which we use at a second home. I pay close to another $1.50 (or more) a gallon for alcohol free fuel. It's less expensive than keeping the additives in the gas hungry little devil. The consequences of having an big outboard ruined by "bad" gas would make the extra fuel cost pale by comparison.
 
Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
I don't know how much fuel you use; or if
  • You only use Ethanol Free gasoline; or,
  • If you treat the gas in your tank to mitigate the impact of the alcohol additives, etc.; or,
  • If you just ignore the issues.
I would suggest that using a larger tank could impact your outboard and the fuel system.

My view, is that decision might be informed by the convenience of the proper fuel availability, your range of uses of the fuel, how often you refuel, etc.

We have a some "dingy fuel" which I keep in a small jug for our 4hp, 2-stroke outboard that is over 30 years old. We through more fuel away than we use over a season. We keep additives in the fuel to mitigate the impact on our old 2-stroke, always burn all the fuel out of the carb each time at the end of the day, etc.

We also have a 24' center console powerboat which we use at a second home. I pay close to another $1.50 (or more) a gallon for alcohol free fuel. It's less expensive than keeping the additives in the gas hungry little devil. The consequences of having an big outboard ruined by "bad" gas would make the extra fuel cost pale by comparison.
Thanks for the detailed response, to your specific inquiries:
  • You only use Ethanol Free gasoline; "haven't spent anything on gas yet, planning on ethanol gas with treatment. I'm thinking the 4 stroke minimizes the need to go w/ethanol free gas. Correct me if I'm wrong.
  • If you treat the gas in your tank to mitigate the impact of the alcohol additives, etc.; or,
    " I religiously treated my Yamaha 150 2-stroke for 8 years and the ethanol killed me, not sure I really believe in the treatment.
  • If you just ignore the issues. "No I don't ignore the treatment. Though I got totally screwed with treating my 2 stroke, I will continue to treat my 4 stroke.
**Confirmed your statement "consequences of having an big outboard ruined", different topic but it cost me over $6k. Totally horrible. Ended up selling my boat.

Thanks for everyone for all the great feedback. I think I'm leaning toward a 6 gallon take with a 5 gallon plastic jerry can. This will allow me to more easily carry the 6 and 5 gallon take to the gas station if/when needed.

The comment of taking the ICW to port charlotte and the keys is spot on. Did it a couple of times via my power boat. Powering at times would be critical.

Greatly appreciate all the input. Starting this thread, I was leaning to the 12 gal but now going toward the 6 gallon and 5 gallon jerry can.

Best to all
Jeff
 

SG

Feb 11, 2017
1,455
J/Boat J/160 Annapolis
4 stroke engine doesn't make ethanol gas more tolerable. In fact it's worse, in my opinion, because the electronic ignitions and complexity of the engines is a lot worse than a "simple" 2-cycle.

The treatment additives, in my opinion, mitigate the problem of ethanol gas -- they don't "cure" it. If you cycle your gas through a lot -- then you're less likely to have an issue. Cars can get by because they pass gas through a lot more than you're like to be cycling fuel.

People with gasoline powered boats spend all the money they do on ethanol free gas for a reason. (If you go 25 km "out" and 25 km "back", and burn [say] 25 gallons of fuel on little excursion of four hours, you're going to be paying about $100 for ethanol FREE fuel, vs. $60 if you use ethanol "regular" stuff. The people paying this know more about engines and fuel systems than most of us here; and, they don't piss away money for nothing.

Anyway, Jeff: If you have frequent available fuel fill-ups available, I'd be more likely to use a smaller tank and cycle your fuel more often.

We have (on our J/Boat) about 160 gallons of diesel fuel in two hard tanks and two inflatable tanks -- but we cruise over 650 miles back and forth, each way, to Maine from the Chesapeake most summers. (The trip up there is almost always, non-stop.) If we just "hang-out" in the Chesapeake, then the extra tankage is a liability, not an asset. If the diesel tanks get "gunked" up, they cause a bunch of problems. (We have fuel polishing, and religiously cycle the fuel out of the inflatable tanks into the hard tanks where we can polish the fuel. We have an aggressive additive program to protect the fuel, don't fuel-up in the rain, etc., etc. We had one "bad" experience which required cleaning the tanks about 12 years ago and don't want to ever experience that cleaning bill. Fortunately, we didn't notice the problem by having the engine or generator fail to run. We noticed the signs of the "gooh of life" in the multiple RACOR filters. :^))) )
 
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Jun 2, 2004
2,867
Hunter 23.5 Fort Walton Yacht Club, Florida
If you use two six gallon portable tanks you would not need to transfer fuel from one tank to another. This would very nearly eliminate the possibility of spilling any gas.
 

SG

Feb 11, 2017
1,455
J/Boat J/160 Annapolis
I would guess that the 6 gal plastic tank weighs a bit over 7 pounds empty (not heavy duty) and the gasoline a bit over 6 pounds/gal. Do you have room for two of those, Jeff? On you boat hanging 40 plus pounds on a rail would change the trim in light air. You clearly shouldn’t be putting the tank down below.
 
Aug 22, 2017
1,561
Hunter 26.5, 212, 170 West Palm Beach
My opinion is to go with a six gallon tank... then carry a couple of 5 gallon jerry cans... because... you can remove them and refill without taking the boat out of the water. It will leave your more options for refueling. ...
This is pretty much in line with my thinking. I don't like a tank that is too big because that is an invitation for letting your fuel get older than you want it to be. If the gas in your jerry can starts to get old, you can just dump it into a car's gas tank to use it up. It's not so easy to do that with fuel that is already in a boat tank.

If you decide that you want a 12 gal tank, & you plan to pass by Palm Beach some time in the near future, let me know. I probably have one kicking around that I don't use anymore.
 
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Jan 31, 2009
5,252
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
.. I think I'm leaning toward a 6 gallon take with a 5 gallon plastic jerry can. This will allow me to more easily carry the 6 and 5 gallon take to the gas station if/when needed. ..
In hindsight that is a good plan. I have Tohatsu 4 strokes and they can take the blend but if available I'll spend the extra on alcohol-free gas. Can usually find it at marinas and some stations.

Sumner
===========================================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...

MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas
 
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Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
I would guess that the 6 gal plastic tank weighs a bit over 7 pounds empty (not heavy duty) and the gasoline a bit over 6 pounds/gal. Do you have room for two of those, Jeff? On you boat hanging 40 plus pounds on a rail would change the trim in light air. You clearly shouldn’t be putting the tank down below.
Thanks for the reply SG. I'm definitely not putting any gas containers below. I also wasn't even thinking of hanging any containers on the rails. My plan/thinking is to now go with the 6 gallon tank and get a 5 gallon jerry can. Was thinking of putting the jerry can between the new 6 gallon tank and the transom.
 

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Dec 3, 2011
109
Catalina C27 Bellingham
Personally I would never run ethanol fuel in an outboard, and even then I pour anything left over at the end of the season into my Suburban. For my tender I have a small 2 stroke kicker. I buy the canned ethanol free premixed gas from the lawn and garden section of Walmart. It's crazy expensive (towards 20 bucks a gallon) but I only use a couple quarts a year in the little 2.2 horse Suzuki kicker.

I would second the guys saying go with the six gallon. With the weight of your boat that will take you pretty far. I have 2 six gallon tanks in mine I can fill them from a jerry can or can just remove them and fill them on the way to the boat. But like I said I only use ethanol free fuel and if it's gonna sit more then a couple weeks I put it in one of my land vehicles and buy it fresh when I use the boat again.

edited for clarity
 
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Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
Follow up question: Is the location of the fuel tank important? Being totally new to sailing and especially using a portable gas tank, I'm making the assumption I'd place the gas tank where it currently is in the picture. But, I saw on another message board someplace that someone had built a frame type bracket mount on the starboard rear seat and had their 3 gallon tank located on the bench and used the mount to keep the tank in place.

I understand displacing some weight but a 3 gallon tank would weigh less than 20lbs.

Is the location of the tank important to how the engine runs?
 
Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
SG & Vetch, thank you both for the valuable ethanol info. I was totally unaware that the treatments I had been adding to my previous boat did so little. My only real gas management I did was to keep my 60 gallon tank almost always full (to avoid and condensation/moisture from developing in the tank), I religiously added Sta-Bil and always purchased gas from the same station.

I was also under the impression that a 4 stroke would have no issue with ethanol.

I just did a quick search and I have 3 gas stations w/in 2.5 miles that have ethanol free gas. Definitely the way I'll be going.
 
Jan 22, 2008
7,032
Beneteau 323 Annapolis MD
Space on my B23 5 always a concern, when I bought my Honda 8 outboard it came with a 6-gallon tank. When the guy reached up the shelf for it, I asked if I could have the 3 instead. He looked at me like , was I serious. I was. Whatever you get, make sure you can tie it down securely. One saying is, "the only time you can have TOO MUCH gas is when there's a fire".
 
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