GT40 - electronically rev-limited?

[davidr]

Anyone know whether the GT40 is electronically rev-limited to the 4,800 rpm redline?

I've got a mid-90's SN w/GT40 & 1.23 transmission, I'm seeing 5,200 rpm indicated at WOT (I believe the prop is original equipment, 4-blade OJ) which worries me a bit. On the other hand I recently noticed the tachometer behaving strangely, intermittently reading 1,200 instead of 850 at idle, and once jumping momentarily to 2,000 with no change in the sound of the idle.

[bkhallpass]

davidr,

I have not been able to confirm, but I don't believe 4 blade props were
standard until 1997.

BKH

[Mikeski]

David,

Those tachs are notorious for switching modes between 8 and 6 cylinders. Take it out and fiddle with the selector on the back of the tach or take it apart and spray a little contact cleaner on the rotary switch. I had to fiddle with my 95's about once a year that past couple years until I sold it last year.

[davidr]

OK BK, that's a possible clue, thanks.

Mike, that's a reasonable idea. If I can open the tach I may try hardwiring the 8cyl connection...

I skimmed through the GT40 reference/repair manual and found no conclusive evidence of an electronic rev-limiting function at redline.

[darrel409]

I have a Pro Boss motor in my SN very simaler to a GT40. Early this past winter i was testing different props. While running a smaller 4 blade i ran rpms up to about 5000 and then it would go into limp mode.
Concur w/ BKH as the 3 blade OJ was stock prop.

[Mikeski]

I believe the 4 blades came stock first in 1997 with the TSC hull.

[nms1991]

Yes the Gt-40 is rev limited at 5250 rpm and it is called soft touch rev limiting it cuts out cylinders by shutting injectors off to control rpm. The Protec system has it also and so does the other Efi engines as a protection for the engines.