A 3 gallon gas tank should be plenty for your 6 HP Evinrude with gas to spare.
CRA Jr
The propeller size on an outboard engine, is dependant on the application. The size of the boat, and more particularly the weight it will carry, determines the propeller size.
The Mercury 40 HP outboard typically requires a fuel line size of 5/16 inch (8 mm) in diameter. This size is designed to handle the fuel flow necessary for optimal performance of the engine. It's important to ensure that the fuel line is compatible with the type of fuel being used and to check for any specific manufacturer recommendations in the owner's manual.
As of January 2011 Evinrude does not. In 2010 they came out with a 15 hp E-Tec outboard motor. This is basically there 25hp model regulated to do no more than 15hp. If you look at these motors side by side, there the same size and weight. The weight of the 25 hp E-Tec 20" shaft is between 150 lbs and 183 lbs, depending on the model. The problem is that the 15 hp models weight the same and this too heavy for some boats transoms. In my opinion it's a joke, Evinrude did it so guys could by a smaller matching "kicker" outboard for trolling, next to there bigger higher outboard motor. Lets hope that in the very near future they will come out with a 9.9 or a 15 hp E-Tec that will have the lower weight. These outboards should only be weighing in the neighborhood of 80- 115 pounds. Hope this helps! Chris
For a 2005, Mercury 3.3 hp outboard, a NGK BPR6HS.
OD281588
The key features of the 9.9 Yamaha 4-stroke outboard motor include its reliable 4-stroke engine, compact size for easy handling, efficient fuel consumption, quiet operation, and smooth performance on the water.
The fuel tank size for a Mariner 3.3 hp outboard motor is typically around 1.1 liters (approximately 0.29 gallons). This compact tank is designed for small boats and provides sufficient fuel for extended use while keeping the overall weight and size manageable. Always refer to the specific model’s manual for precise specifications.
not sure how wide your Jon boat is but I would go with a 3.5HP or 5HP outboard no bigger
175/150
550 cca
The key features of the Yamaha 9.9 four-stroke outboard motor include its reliable four-stroke engine, compact size, and efficient fuel consumption. Benefits of this motor include smooth operation, reduced emissions, and easy maintenance.
Any place that sells batteries can tell you the correct size to buy.