Re: First post, first boat restore...
For what it's worth, I doubt 5 gals will do, esp tubing. This is my 1st boat, but I've paid for gas at the dock many, many times. 4-5 guys, 1 mid 1980's OB fish & ski, w/ a 70-75HP mid-80's motor and we burned 2 tanks of fuel in 4-5 days (1/2 day the 1st day, and 1/2 the last w/ 3-4 full days in between) on Lake Cumberland in KY. We'd use 20gal +/-. Always left tanks full for next time, and put a tankful in every trip, late the 2nd full day usually. Then 1 of us would go top off while the rest of the crew packed the gear. I think his tri-hull had a 10-12gal tank. Cumberland has some area to cover, and we stretched the boat's legs every trip. But sunrise to sunset we were out on the water.
Of course, it also depends on how 'fully loaded' your boat is, how hard you hammer the throttle, and how much of your running around is done at WOT. An OB's fuel consumption will perform the same as your car's gas mileage does with respect to these variables. Raise any 1 of those, & fuel economy goes down. Raise them all, and it goes down a lot. Running & gunning all day w/ 3-4 kids on tubes, 5 gals won't go to far. Me & my dad slow trolling, or drifting at idle fishing for strippers, we could go all weekend on 5 gals. A family of 3 w/ just 1 kid tubing & mom & dad cruising at 3/4 throttle would be somewhere in between.
If you want more specifics for your engine, you should post as much info as you have in a OB thread for your make engine.
IE:
Thread title: Best guess on Fuel economy of a 115hp 1979 Evinrude XYZ OB motor 3cyl/4cyl/6cyl/V4/V6
Post that in the Johnson/Evinrude OB motor forum & ask everything you asked here, there. In your questions, include everything you know about your boat, how you'll be using it most often, and any details you can. Boat weight wet (full w all fluid & gas), if there is a coast guard capacity/weight/max HP inspection sticker, include those details. Be prepared to get some grief if you are over powering the 1979 Glassmaster. I don't need to max out my motor. I'm putting a 65HP motor on a transom rated for up to a 75HP motor, replacing a 35HP. I expect about average fuel economy, and above average performance with the 65HP. But this 65HP is known for having an HUGE appetite for fuel. I won't be driving it hard, it's a 1960 boat, nor running it for long periods of time at WOT. I intend to run 2 6 gal gas cans full time & carry a small 2-3gal can as a backup/spare just in case can.
See the page below, it lists all the known models of Glassmasters for 1979:
http://boatspecs.iboats.com/Glassmaster__1979/bp/54br1199y
As for the fuel & a vent hose, or venting the area for fumes, you'll need to provide details. Does your motor need pressurized (2 line) fuel tanks or not? I have posted most of this thinking your 115 would be an OB not an IB/OB or strictly an IB. But w/out details I can't fully answer your vent question. If your running an IB/OB or IB, there will be a bilge ventilation fan needed to remove any & all fumes from the motor doghouse prior to starting the motor. These IB/OB & IB motors require fresh air to be directed into the doghouse to feed O2 to the motor, so this is often done w/ vented louvers on the motor cover or along the outside hull of the rear gunnels. This is not to be considered instead of a bilge fan, they are 2 totally separate ventilation functions that need to be operational & functional independently. Although the bilge fan may exhaust near or just behind the louvers.
Look through CL local to you & in nearby areas. You may find a low cost gas tank that fit's you boat & your needs. But inspect used gear VERY CAREFULLY prior to installation & use. Tanks need to be pressure tested to ensure they don't leak fuel.
Also be considerate of how the original manufacturer laid out gas tank & battery storage, and your 'new' 115 OB's weight. Balancing the battery left, & the gas tank to the right of the motor(the heavier to the port side, opposite the driver), or 1 gas tank on each side w/ battery in the middle. Maybe moving the battery or gas tank up to the bow to offset the increase in weight of the new larger motor.
Good luck! & ask as many questions as you can. Be safe & enjoy putting it back into service!
Safe & happy holidays this season!
I love it when that happens, 'cause it don't happen very often!
