Mercury 300x oil injection hose routing

**Sea2jet** · 01-07-2017, 11:20 AM

I'm just curious. On page 4A-35 of the service manual they show the port side of the 2002 and up engine depicting the oil pump hose routing into the crankcase. On the next page they show the starboard side with hoses running into the cylinders. That's not depicted anywhere in the manual for the port side. Are they only on one side and what's the reasoning for it? The 3 lines going into the sides of the cylinders are depicted in this photo. Thank You.

**Kevin_From_NJ** · 01-11-2017, 05:10 PM

The hoses that you see there in that picture are not the oil injection hoses, those are the bleed lines. The oil injection hoses on a 300x go from the oil pump to the fittings on the reed plate. Hope it helps.

Kevin

**Kevin_From_NJ** · 01-11-2017, 05:16 PM

Here is the oiling system diagram

**Sea2jet** · 01-11-2017, 05:23 PM

Hi Kevin. Thank You. Any idea what the bleed lines do and why only on one bank of cylinders(Starboard side and not on the port)? Just curious.

**Kevin_From_NJ** · 01-12-2017, 12:22 PM

Originally Posted by Sea2jet

Hi Kevin. Thank You. Any idea what the bleed lines do and why only on one bank of cylinders(Starboard side and not on the port)? Just curious.

The bleed system is used to re-route unburned fuel that puddles in the engine to try and stop the engine from "loading up". Mostly idling for long periods will cause the fuel to puddle.

The port side does have some bleed hose fittings but they are not by the cylinders like the starboard side. Here are a couple diagrams of the bleed routing.

**Kevin_From_NJ** · 01-12-2017, 12:22 PM

Starboard Side

**Kevin_From_NJ** · 01-12-2017, 12:23 PM

Port Side

**Sea2jet** · 01-12-2017, 12:26 PM

Thanks for the explanation Kevin. It's very much appreciated. Mike

**Snotrekie** · 01-12-2017, 01:17 PM

do these lines exist in a 2.5 nic motor?

**vnemous** · 01-12-2017, 03:35 PM

I find when I idle my 300x if I trim it up a little it helps with the puddling JMO

**Chaz** · 01-12-2017, 06:51 PM

Originally Posted by vnemous

I find when I idle my 300x if I trim it up a little it helps with the puddling JMO

I thought you did that so everybody could hear the exhaust churdlin above the water line ...

**vnemous** · 01-12-2017, 07:08 PM

Originally Posted by Chaz

I thought you did that so everybody could hear the exhaust churdlin above the water line ...

Well you and I know thats the real reason

**Kevin_From_NJ** · 01-12-2017, 07:08 PM

Originally Posted by Snotrekie

do these lines exist in a 2.5 nic motor?

The only one I have seen is the 245 carb motor that has the bleed fittings by the cylinders. I believe that non of the EFI engines have them. I could be wrong tho, I've been wrong before.