Plenum & Injector Housing Porting - ZR-1 Net Registry Forums

Marc Haibeck · 06-22-2018

Mercury Marine corrected the port mismatch problem in '93. It was part of the 405 hp upgrade. They CNC blended the injector housing ports 1.5" down the port. They also increased the plenum port diameter from 33 to 34 mm. That's why porting an early engine well will add 35 hp. Only 20 hp can be gained on the '93 and up engines.

06-22-2018	#11
Marc Haibeck Join Date: May 2007 Location: Addison IL Posts: 250	Re: Plenum & Injector Housing Porting Mercury Marine corrected the port mismatch problem in '93. It was part of the 405 hp upgrade. They CNC blended the injector housing ports 1.5" down the port. They also increased the plenum port diameter from 33 to 34 mm. That's why porting an early engine well will add 35 hp. Only 20 hp can be gained on the '93 and up engines.