4.3 mpi rpm limiter exact setting

[QBhoy]

Hi
ive looked online for last wee while but can’t easily find the exact rpm limiter setting for the 4.3 mpi.
trying to prop a boat for starters and don’t have any exact indication with not having the smart craft or vessel view set up yet. On a friends new boat and wanting me to have a go at a likely prop for him ASAP.
I know that the rpm range is 4400-4800 but it’s hitting the limiter currently with moderate trim. Dash tachometer saying it’s at a little over 5000 rpm when it does but I’m thinking that the limiter is likely around 4950. Assuming that because I know my v8 mpi with its range being 4600-5000 rpm will hit its limiter at exactly 5150 rpm consistently.
thanks guys.

 

[alldodge]

Don't know, but once any motor gets close to the manufactured WOT specified, the motor has passed the max torque and torque is being reduced as rpm goes up. Getting it past 4800 is not gaining much except rpms and vibrations

 

[QBhoy]

Don't know, but once any motor gets close to the manufactured WOT specified, the motor has passed the max torque and torque is being reduced as rpm goes up. Getting it past 4800 is not gaining much except rpms and vibrations

Totally agree AD. Don’t want it on the limiter. Just wondering proactively what the exact rpm is when it limits. It limited with 3 up and fuel onboard. Was more trim to go if it didn’t limit. The alarm sounded to tell me it was limiting but only had the dash tachometer as an indication...and I know how terrible they are, from comparing my own boats to the ecu reading on smartcraft.
The owner of the boat wants me to have a stab at a prop size to suit, just from the data we took yesterday. So if I knew that it was limiting at a certain figure, I could have a best guess for starters. I have the GPs figure of 50 mph on the nose. Know the gear ratio. Only thing is the prop is a spitfire 4 blade ally. Sometimes a hit or a miss going from that to a stainless 3 blade. I think it will be about 4950rpm at the limiter, if my V8 mpi version isn’t anything to go by. I know mine limits at exactly 5150rpm (150 rpm over the 5000 rpm max range figure) the 4.3 mpi max end of the range is 4800...assuming it’s safe to add on 150 rpm for the limiter maybe. Dash said just over 5000 when the alarm sounded.

 

[achris]

I can confirm the rev limit of a 4.3MPI is 4950... It's in the ECU downloadable information data.. See below.

Chris.......

 

[QBhoy]

I can confirm the rev limit of a 4.3MPI is 4950... It's in the ECU downloadable information data.. See below.

Chris.......

Ah. Brilliant. Some man Chris. Thanks for that. Just what I need. Suspected it would be around that.
allan.