Is my Mercruiser fuel injected or carb?

[jimmbo]

The Fly in the Ointment, is what is the Airflow capacity of the OEM Carb and the Characteristic of the OEM Intake. If the Intake can flow more are and the OEM carb was the restriction, then yes the Holley would improve the power. If the Intake is the Restriction, then a bigger carb, will introduce problems unseen before.
I was lucky, Volvo put a very nice 4bbl Intake on my 5.7 and put the 2bbl 500 Holley on an Plate to make it fit. The 5.7 needs a bit more airflow than the 500 can provide, well it can provide more, but the Pressure Drop is too high.
I did put a 650cfm Holley Spreadbore on, and gained about 500 rpm, which required more prop to keep the Rpms within the WOT range. The Holley is a Vacuum Secondary Carb, and the Secondaries have never opened fully, as it still more carb than a 5.7 at 5000 rpm needs. More Pitch also reduces Holeshot, even though the engine makes more HP at the top end, low rpm performance suffers. The very small Primaries on the Spreadbore do help retain some low end Torque. Overall I gained 6 mph which put boat deep into the mid 60s

 

[Scott06]

The mercruiser 2 bbl intake is low rise and tame from a perf standpoint. The stock VP manifold Jimbo mentions is a performance design like the edlebrock and the no name cast iron one i use.

i bought my engine as a partial from michigan motorz (“Silver Package”). Came with the cast iron intake and a edlebrock 1409 600 cfm carb. They rated it at 260 hp saying the intake was worth 15 hp over the stock one…bow true that is i have no way of knowing. all i can say is it works fantastic and has excellent midrange throttle response. Would think it would be worth 15-20 hp gain in your application. Probably give you 2-3 mph gain on top end maybe more.