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Can you get too big of a gas tank?

Dec 3, 2011
109
Catalina C27 Bellingham
I wouldn't think location of the tank would matter much. So long as it's close enough that the fuel pump can suck fuel from it. Lower in the boat would be better but I wouldn't store gas in the cabin or where the fumes can get in easily.

The biggest concern would be weight aft. if it makes your boat too heavy at the stern. That can always be balanced by weight forward. ie. chain rode or water under the V-birth.

Edit-
Let me clarify.... water in a tank in the V-birth. Want to keep other water out of the boat.
 
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Aug 22, 2017
1,561
Hunter 26.5, 212, 170 West Palm Beach
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?
That location is where I would put it. If you find that it is in your way there, then consider moving it once you know that an actual problem exists.

If you are going to have a 5 gal jerry can, then a 3 gal tank is probably plenty. In fact, a 3 gal tank & a 2.5 gal can is probably enough, unless you are planning a multi-day adventure. Smaller cans/tanks save space. My Carolina Skiff with a 25hp would burn about 6 gal on an average day.

Maybe get a 3 gal tank, a 2.5 gal can & a 5 gal can. That way, you can bring the big back-up can on days that you plan to go further & have more space on the days that you plan to stay local.
 
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Aug 22, 2017
1,561
Hunter 26.5, 212, 170 West Palm Beach
...I was also under the impression that a 4 stroke would have no issue with ethanol. ...
You definitely do not want to leave ethanol gas to sit in your boat motor or boat tank for more than a little while. If you burn up all the gas in a few days, then ethanol is OK, but it does very bad things when it sits.

In my fishing boat, I would bring a 12 gal tank or two of cheaper ethanol fuel to burn on the way out to the fishing grounds, then switch over to the main tank with ethanol free before returning to port. That worked OK because I was 100% sure to have the entire fuel system full of ethanol free before I shut the motor down.

You can find stations that carry ethanol free gas here - https://www.pure-gas.org/
 
Jun 24, 2010
188
Macgregor 25 South Hero. VT
Thank you JimInPB for the link to find ethanol free gas. That is a great help.
 
May 16, 2011
515
Macgregor V-25 Charlton, MA- Trailer
This is what I did. 6 gallon is fine. 9.9 Johnson sips gas. Motored from Martha's Vineyard to Fairhaven and still had 1/3 tank.
I used composite deck spindles for the frame, decking for the top and white plastic board for the front. Stainless hardware. Gas line run through 1" hole cut with hole saw then edge routered. Tank was a PIA on deck and dangerous if ever in a knock down.
 

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May 16, 2011
515
Macgregor V-25 Charlton, MA- Trailer
On one big trip from the Cape Cod Canal to P-Town I brought another 6 gallon jug. Easy enough to lash on the deck. Good luck with the boat!
 
Sep 25, 2008
863
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
I built a permanent fuel locker that holds a 6 gal tank and two 1 gal fuel cans for emergency reserve. I have a fuel/water filter mounted in there too. The fuel line runs through the open area inside the back of the boat and exits the transom near the engine mount. The fuel line that is inside the boat is inside a larger hose, that is sealed off from the inside, so there is no way any fuel or vapors can get inside the boat.
 
Jul 29, 2010
1,362
Macgregor 76 V-25 #928 Lake Mead, Nevada
To theCuscus, as jjsbigs said nice work. Wish I had your skills. I always use the 3 W's, Weight, Weight and Weight. Pints a pound the world around. 6 gals=24 pounds, 12=48 and so on. Agree with Vetch, That's lot of weight in the stern. Had Merc 7.5 2 stroke with 6 gallon tank. Got us from San Pedro to Catalina (25 miles) with plenty to spare. Top off at fuel dock. Would motor over in AM, no wind. Have Honda 7.5 4 stroke with 3 gallon tank. No problem for weekend on lake.
 
Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
This is what I did. 6 gallon is fine. 9.9 Johnson sips gas. Motored from Martha's Vineyard to Fairhaven and still had 1/3 tank.
I used composite deck spindles for the frame, decking for the top and white plastic board for the front. Stainless hardware. Gas line run through 1" hole cut with hole saw then edge routered. Tank was a PIA on deck and dangerous if ever in a knock down.
Awesome and thanks for the idea. I was toying with the idea of building something but wasn't sure what or how to. I will definitely add this to my list of to-do's.
 
Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
I built a permanent fuel locker that holds a 6 gal tank and two 1 gal fuel cans for emergency reserve. I have a fuel/water filter mounted in there too. The fuel line runs through the open area inside the back of the boat and exits the transom near the engine mount. The fuel line that is inside the boat is inside a larger hose, that is sealed off from the inside, so there is no way any fuel or vapors can get inside the boat.
Great job!!! With M25 isn't open all the way to the aft/stern of my boat. I have a fiberglass wall with large blocks of Styrofoam behind it, maybe like 2 to 3 feet.
 
Aug 22, 2017
1,561
Hunter 26.5, 212, 170 West Palm Beach
.... I always use the 3 W's, Weight, Weight and Weight. Pints a pound the world around. 6 gals=24 pounds, 12=48 and so on. .....
That pint=pound thing works in the kitchen when you are measuring butter for baking and it works for water, but it does not work for gasoline. Different materials have different densities. Gasoline is just over 6 pounds per gallon. Motor oil is just over 7 pounds per gallon & water is more like 8 pounds per gallon. Also, there are 8 pints in a gallon, not 4. 6 gallons = 48 pints, or 24 quarts. 6 gallons of gas is a little over 36 pounds, actually closer to 37.
 
Jul 29, 2010
1,362
Macgregor 76 V-25 #928 Lake Mead, Nevada
Point taken. Just sayin' about the weight. Any is too much!!
 
Sep 11, 2015
1,260
Macgregor 25 Oregon lakes
Similar idea to others using a 6 gallon tank, which is more than enough for an extended weekend including no wind sightseeing, fishing (trolling) etc.
One point I would make is a 6 gallon tank fits well in that area, but if you're not planning an extended trip nothing says it has to be filled with the full 6 gallons!... just sayin. :)
P1030515.jpg
 
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Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
Similar idea to others using a 6 gallon tank, which is more than enough for an extended weekend including no wind sightseeing, fishing (trolling) etc.
One point I would make is a 6 gallon tank fits well in that area, but if you're not planning an extended trip nothing says it has to be filled with the full 6 gallons!... just sayin. :)
View attachment 161489
I like this idea also. How is the cover/top kept in position? Also, I have a 3 gallon tank and I'm now planning on getting a 6 gallon and use them as needed. I plan on doing quite a bit of motoring so I shouldn't have any challenges of having old/stale fuel in either tank.
 
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Sep 11, 2015
1,260
Macgregor 25 Oregon lakes
I like this idea also. How is the cover/top kept in position?
cover sits on cedar strips bolted to the sides. it just lifts off to access tank etc. the tank sits on a base frame, also made of cedar, which is routed out for the tank to sit in securely. drain slots cut in the bottom.
P1030512.jpg
 
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Dec 1, 2018
14
Macgregor M25 Still working on it Safety Harbor Florida
cover sits on cedar strips bolted to the sides. it just lifts off to access tank etc. the tank sits on a base frame, also made of cedar, which is routed out for the tank to sit in securely. drain slots cut in the bottom.
View attachment 161505
Thanks RussC for the additional details.
 
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Jun 3, 2004
1,832
Macgregor 25 So. Cal.
Gas with alcohol---------------------Up to 10% Alcohol No marking on pumps
Gasohol-------------------------------Up to 15% Alcohol Pump must be marked
Ethanol/E85---------------------------85% Alcohol Obvious

Gas with alcohol will run in carb type engines without re jetting but millage and hoses, seals and fiberglass tanks might be affected.
Gasohol needs to be re jetted for and besides the above is hard on aluminum will destroy fiberglass tanks.
E-85 MUST be re jetted for and will damage all the above.Will cause a sever lean condition and ruin the engine.
VP C-12 is a leaded race gas and sells for about $100 for a 5 gallon metal can and be stored for around 5 years if kept sealed. I will make your motor run better than it has ever ran. CAUTION DO NOT RUN IT IN ANYTHING THAT REQUIRES UNLEADED FUEL OR HAS A OXYGEN SENSOR OR A CATALYTIC CONVERTER!!!!!!!! Sold at most motorcycle shops or they can order it for you.