Fuel tank for 23ft runabout

[rogergray]

I am restoring an old mahogany 23ft runabout, which should have an inboard engine though it is missing. I do have a fuel tank, which is fibreglass, and I am not sure if it is suitable for petrol. Can someone help me with this? Also, apart from the filling pipe, there are three other smaller holes in the side of the tank, and I am not at all sure what they are for. photo available if someone would be kind enough to help with all this.
Roger

 

[Forbsie]

At an uneducated guess - breather, feed and return.

 

[burgundyben]

GRP tank is fine for petrol or diesel, most likely the other holes are for breather, this needs a pipe to be routed high up under the deck and overboard with a suitable cover to keep rain/spray away, and a supply to the engine and a return if diesel.

The fuel is a big weight and you need to be carefully considering the position of the tank as it will affect trim and hence economy/performance.

Not sure of the hull shape but I would suggest choosing your engine and gearbox, planning and execute the installation, launch, look at trim and decide where best to position tank.

Hope this helps.