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Monsoon 325 - Throttle body fuel injection or MPI?


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Considering the purchase of a 2002 Sunscape 23 LSV with the Monsoon 325 hp engine. It will be my first boat. Haven't been able to determine if it's throttle body injected, or if the injectors are located at each cylinder - MPI? I believe there's a flame arrestor on top of the engine, that's why I think it might be throttle body injection. But references I've seen on this site refer to the engine being MPI.

If it's throttle body injected, is there any disadvantage to this setup over MPI?


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TBI is really just a glorified, computer controlled, carb. It doesn't disperse the gas in a mist into each cylinder like better EFI systems do. Still goes thru the intake manifold to do that.

I had TBI on my 1994 MC. Would be surprised to see it still sold in 2002.

Edited by Bill_AirJunky
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Bill_AirJunky is correct. It is my recollection that the '02 monsoon was an upgrade motor for the standard. It is also my recollection that the standard motor was either 300 or 310 hp TBI and the Monsoon is MPI. I could be wrong though.

On a side note, what are the details on the 2002 Sunscape 23 LSV you are looking to purchase. I only ask because I am selling my pristine and immaculate '03 23 LSV Sunscape. It is loaded, including the 375 HP Hammerhead motor. I have it listed on the forum if you want to take a look. The price is somewhat negotiable.

Edited by Roselaw1
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The '02 monsoon engine is indeed MPI. There is very little advantage of MPI over TBI thought. Both work on just two channels, which means on MPI, 4 injectors are firing at the same time, three of which are just flooding the port with fuel that has no where to go. If you want 8 injectors firing independendly of each other, when its intake valve is open, you need sequential MPI. TBI actually followed the "glorified carburetor", called an MC (mixture controlled) carb. It too worked on a two channel circuit using the same wiring and software as todays TBI and MPI system.

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  • 3 years later...

Then why does my 02 Mpi have power wires going to each injector and a computer to tell them when to open?

My 03 Moonson is also a MPI, you can see 4 injectors on every side....

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Then why does my 02 Mpi have power wires going to each injector and a computer to tell them when to open?

If you look at the wiring diagram for an '02 Monsoon, you will see that it does, like electricjohn says, have only two channels coming out of the ECM to controll all 8 injectors. The ECM can not fire a particular injector at a particular time. They are fired 4 at a time.

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It is called batch firing. Notice there are only three colors of wires on the injectors. Channel one, channel two, and common.

  • Like 1
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Batch fire on the Monsoon is still better than TBI. Honestly batch fire isn't really a big deal in a boating application. Somewhat hurts fuel efficiency in an automotive application. It is also harder to tune cylinder to cylinder in high HP applications, not to say there aren't 1000+ HP cars running a batch fire setup.

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