2000 7.4L MPI 310hp T.B. gasket mismatch
 

I brought home my boat from storage and was doing some checking around to see how things held up over winter.

I've had the boat a year now but never really looked into the throttle-body before. With the motor not running I opened the throttle to wide open. That's when I see an obstruction in the lower part of the opening. :confused: The gasket that goes in between the T.B. and the cast elbow that runs to the intake plenum is in the airpath. The gasket is not matched for the opening and is blocking airflow. I couldn't believe it!:mad:

Has anyone ever seen this before?

I just talked to a mercruiser mechanic that looked up my motor on a microfische and found that a D-shaped gasket is correctly placed in between the T.B. and the intake elbow. Why would Mercruiser not use a gasket with a round hole for this T.B. assembly? Any other guys out there with a 7.4L MPI motor look into their throttle bodies lately? :confused:

Just got off the phone with Crocket marine about the miss mach they know little about it. They seemed to think the throttle body might be a bit large and this is a way to compensate. I also did some calculations on the size of the flame arrestor and thought it is too small to properly flow around 700 + cfm. One fellow stated he removed his and felt no differance. Maybe the gasket is the restrictive part. Might have to try opeaning up the gasket and see what happens. It woud be nice if it ended the soot on the transom condition.

I have the same soot problem on my transom too. There must be something to this.

Hey EX20 just read yor post. I am going to look tomorrow at my 2000 model 7.4's. I'll let you know what i find. Keep us posted on what you do to remedy the situation.

Sounds like a good place for fuel to puddle then run into the runners instead of being atomized.

the gasket is about 1" behind the butterfly plate in the throttle body, (no fuel is added yet) I have no idea why they used that gasket, mine has it to. maybe it is used for idle quality or tuning, but it takes up about 1/4 of the space in the throttle body. anyone what to test this with it and then trim it and see what happens?

Guessing that merc put it there because if removed the 7.4 out performs the 502. Going to purchase a new gasket this weekend but wont be running the boat till the first weekend in May. Also have been trying to purchase a K&N filter but they keep sending me the wrong catalog and it takes 3 to 8 months to get it.

I dont think the tech surport at k&n knows the differnace between the efi and mpi I believe it needs a adapter to fit

The 7.4 dosent need an adapter because the conection is round the mag and above is rectangular