I ordered some 1/2" fuel hose online. Went to replace all my fuel lines today and discovered the lines going from tank to shut-off valve and on to the filter housing are 5/8".
Is this normal or did the prev owner "upgrade" the fuel lines? One of the lines had a date of 1991.. Boat build was started in 1989 and completed in 1990.
All the hoses from the filters up to the carbs were 1/2".

My 27 have a 5/8" hose from the tank to the valve and all the way to the filter.

Humm, OK. Sounds like it's original. At the fuel tank pick-up tube connections it looks like it has a reducer screwed in there to get down to 5/8"!! They must have had BIG plans for these tanks.

When I was calling around locally for some 5/8" fuel feed hose, I got a lot of confused marine parts salesmen. They had never heard of even 1/2" fuel feed line. Luckily the 5/8" is also used for the vent hose on a lot of boats so they had some in stock.