[kajroxygurl]

I owned a 77 Sceptre I/O and it had a 85 gal tank of which the specs said would give 72 gals useable. I would think your tank is larger than 58 gals. The 1978 spec sheet says a 40 gal optional tank was available as an option and it could be put in the forward storage well. The outboard model had a 100 gallon tank (useable gallons). If your tank is only 58 gallons then I think there has got to be more space under the floor for a larger tank. Good luck.