Scherbacj Posted October 16 Share Posted October 16 Has anyone here removed the EFI/Air Filter restrictor plate from their 75 HP Mercury? I’m trying to find a parts diagram so I can see which part to remove and get an idea of how easy it is, but I can’t find much online. The diagrams I can find don’t even show the intake. It’s a 2023 if that matters. Does anyone have a parts diagram that shows the restrictor plate? can anyone comment on the performance difference before/after the mod? Quote Link to comment Share on other sites More sharing options...
Super User Way2slow Posted October 16 Super User Share Posted October 16 I don't know much about Mercuries but know a lot about motors. Whether it's safe to do or not is going to depend on the ECM and Mass Air Flow Sensor, if it has one. It's naturally going to increase air flow into the motor, meaning it going to need more fuel to maintain the proper fuel air ratio. If it's basically a dumb system that is preset at the factory and the ECM can't compensate for that increase flow, it's going to make the motor run leaner. This will give it a few more horsepower but will also raise the exhaust gas temperatures, possibly to the point of cause pre detonation (which damages pistons and breaks rings) or even enough to melt the center out of the piston. Neither of which Mercury would cover under warranty because you modified the motor. One cool morning (cool humid air makes more HP) you head out WOT down the lake thinking "man this thing is running good" and suddenly you hear this sickening sound that a melted piston makes, and the motor loses power, it's going to ruin your day. You might think you can just put it back before taking it to the shop, but "ANY" mechanic will know what happened as soon as they pull the head off. With all that said, I'm not saying you can't but without some way of measuring EGT's or fuel air mixture, you are rolling the dice, and you might end up rolling craps. I personally would not want to risk the price of a new power head for a couple more HP. 4 Quote Link to comment Share on other sites More sharing options...
Rockhopper Posted October 16 Share Posted October 16 That about covers it. Quote Link to comment Share on other sites More sharing options...
Super User WRB Posted October 16 Super User Share Posted October 16 The engine component to change is the prop to gain a few MPH. Proper balance weight load and prop depth for your boat doesn’t cost anything to gain a few MPH. A safe engine mod are exhaust horns to increase HP about 10%, this requires a knowledgeable engine tuner. Fooling around with fuel/air mixture you can grenade the power head as Keith clearly discribed. Tom Quote Link to comment Share on other sites More sharing options...
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