Fuel Tank Size

I might have this question in the wrong forum, maybe not..... I guess I did, thanks for the move.

Specifics:
Boat; 18.8' Renken
Engine; MC 120
O/D; #1 with 1:1.98
Prop; 19p
Planned cruising RPM; 3000 to 3500
Speed really is not important, basically I want a steady, get there and get back platform.
Primary body of water: Lake Erie

I'm currently planning to completely reconfigure my Renken 18.8' boat.
I want to install a below deck fuel tank, and I want to carry enough fuel to run for a few hours at a time and not worry about running out.
The current tank is 15 gallons, I'm thinking of at least a new 26 to 32 gallon tank.
If I run the MC120 at 3000 to 3500 rpm I think the upgraded tank size should do find.
I know the added fuel will add weight, I plan to install this larger tank under the deck right on the center line and right on the balance point from bow to stren.

Am I on course or headed for the bottom thinking like this.

Re: Fuel Tank Size

I sure wouldn't go over 25 gals. That is a lot of weight. I carry 25 in my 19 ft. V-hull, I have a V-8 and I can run all day and barely dent my fuel. The tricky part is getting it centered correctly fore and aft. Too far forward and you will plow like a barge. Too far aft, and you will sit in the water like a fishing bobber.
Adding that much fuel is going to effect how the motor runs, how the boat planes, and reduce your gear weight capacity by nearly 100 lbs.

Re: Fuel Tank Size

Thanks Havasuboatman, if you can run a v-8 and just dent the 25 gallon tank maybe I can stay with the 15 pal. capacity I have, just relocate it under the deck.
I'm new to the bigger boat scene and I'm just thinking of the comments I read where fuel usage is measured in gallons per hour. Those comments may have come from guys running 30 footers with twin 496's.

Re: Fuel Tank Size

When I first got my boat the paranoia of running out of fuel was hard to overcome, for the first little while I carried an extra 5 gallons in the boat (just in case) for my peace of mind.

Get a 5 gallon jerry can and strap her down somewhere until you get used to the fuel usage of your boat, today I just set my GPS to alarm when I have travelled 120kms which gives me plenty of warning with a 15 gallon tank on a 90Hp Merc 2 stroke in a 16 ft boat. With that much capacity in a small boat I tend to forget it needs fuel for a few days while I am out camping/fishing.

It will take you a year to get used to it, then it becomes second nature.

Re: Fuel Tank Size

My 18' SeaRay with a 4.3LX MerCruiser had a 35 gal built in tank. I would use about 12-15 gal on the typical outing. Your boat is similar. I would try for a 30Gal tank, if you can.

Re: Fuel Tank Size

My Parker 18 has a 40 gal. tank.
I'll make 3 trips to the ocean before thinking fuel stop.
Big difference in ride between full and 1/4.
I could live easily with a 20 gal. using the 130 hp 2 stroke.