350 mercruiser fuel economy

[THEFERMANATOR]

You need to know exactly which engine you have. 4000 to an early engine is dead on, some turned 4400, and late model vortecs go up to 5k-5200. Also check your outdrive gearing. It sounds like your gearing may be off for a 350 as I would expect a 17 or maybe a 19 pitch prop on that boat, but not a 21 if it has the 1.5:1 lower unit.

[Dr. Hook]

The cover over the flame arrestor says WOT range 4200-4600, engine serial number OD 391290

Is there a number on the block too?

[Dr. Hook]

It also says transom serial number OD 415218 and drive serial number OD 422744

The previous owner did mention the drive was rebuilt.. What components were replaced was unclear however.