Gm vortec marine engine...
 

Can anyone please give me some feedback on the GM Vortech Engine.
How do these compare to the Mercury Racing 500 / 525 efi engines.
How reliable / economical are they?
Any help will be greatly appreciated. Thanks in advance

i run a 350ho vortec with some add ons and its 5500rpms 400hp and its been 8 years and still runs strong

i assume you mean big block vortec? vortec heads are an upgrade over stock 330 hp round port heads, but it isn't a big power motor.

Yes - Big block vortec engine.
How easy is it to increase HP and Torque from the standard engine.
We are looking at over 500hp

not even close...high torque vs high performance

a vortec is a large oval port head. has a large hump in intake port to increase swirl. they were designed as an improvement over TBI peanut port heads. from what i read, you are looking at a lot of port work to make them decent. hand grinding iron heads is time consuming. if you are paying somebody who knows what he is doing, instead of buying a grinder and a copy of Head Porting for Dummies, (i doubt book actually exists) then it will get expensive. you want 500 hp, aftermarket heads or worked rect ports. i don't think vortec motors use forged cranks-pistons. so there won't be much left of orig engine once build is done...