tewks

Hi,
I'm looking for a replacement for a merc 7.4. The engine I have now is a 1997 with the gen VI block with Mark V heads. I've found a couple sources for rebuilt engines, and the cost difference between the Mark V head and vortec head is negligable. I've heard the vortec heads are better. That being the case, anyone know if I can just bolt my existing manifold/carb to the vortec heads and use the thunderbolt V ignition? Or do I need a different timing module? Any advice welcome!
Thank

Pat McPherson

The intake will bolt up, but I would suggest you buy a new large oval port intake to match the L-29 heads. The carb will work the way it is.
The Thunderbolt ignition will work fine, just keep you initial timing at 8° or less. No more than 30° total advance with the Vortec heads.
By the way, I have a 250 hour 1999, L-29 long block I would sell. She was running strong when I replaced it with a 502...