Sounds of a gt40 in SLOW (limp) mode

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Since the topic of SLOW mode on a gt40 came up with a friend the other day I figured I'd make a video so you can hear what SLOW mode sounds like. 
I said to him, let's put a good running gt40 into SLOW mode so you can see and hear what it sounds like and we filmed the results

Here's the video in the link below

Pay attention to the tach

link

First 7 seconds are trying to go over 2700 and you can hear the computer limit the RPM.
8-14 pulled throttle back to about 2500 and it runs normally.
15-18 accelerate again and at 2700 the computer limits speed again
19-25 pulled throttle back and it runs normally again and will run all day long at less than 2700 when in SLOW mode.

There's nothing subtle about it, it'll jerk you back and forth in the seat as it happens and it doesn't smooth out again till you reduce the throttle and your speed is less than 2700 RPM. You can pull back a little on the throttle and cruise all day long at 2600 RPM or any slower speed with your low oil pressure or hi water temperature condition.

Here's the description of SLOW mode from the gt40 manual It does nothing to give you an appreciation for what it feels like in the drivers seat. The video doesn't give a real good appreciation, you have to experience it yourself.

Anybody with a gt40 should put their engine into SLOW mode and go for a ride to feel it for themselves 

It just takes a little jumper wire with alligator clips on both ends and you connect one end to the high temperature switch terminal (or the oil pressure switch terminal) and the other to a good ground on the engine. No wires need to be disconnected from either switch. You start the engine and your check engine light will be on, now go for a ride.

PSA..........no ECM's or any other engine parts were destroyed while doing this..........it'll tell you that your system works the way it should though 

And to get most everything into one thread, here's a link to Marty's gt40 sensors and switches thread with locations and wire colors shown in the pictures

It's a tan/black wire from the oil switch that connects to a green wire at the temperature switch and the green wire then goes into the harness to go to 2 different spots. One is to the ECM and the other is to the Red dash light 

This was a 2000 SAN and everything location and color wise agrees with Marty's 98 SN pictures.

link

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KENO Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11116	Post Options Post Reply Quote KENO Report Post Thanks(0) Quote Reply Topic: Sounds of a gt40 in SLOW (limp) mode Posted: August-28-2023 at 7:53am
	Since the topic of SLOW mode on a gt40 came up with a friend the other day I figured I'd make a video so you can hear what SLOW mode sounds like. I said to him, let's put a good running gt40 into SLOW mode so you can see and hear what it sounds like and we filmed the results Here's the video in the link below Pay attention to the tach link First 7 seconds are trying to go over 2700 and you can hear the computer limit the RPM. 8-14 pulled throttle back to about 2500 and it runs normally. 15-18 accelerate again and at 2700 the computer limits speed again 19-25 pulled throttle back and it runs normally again and will run all day long at less than 2700 when in SLOW mode. There's nothing subtle about it, it'll jerk you back and forth in the seat as it happens and it doesn't smooth out again till you reduce the throttle and your speed is less than 2700 RPM. You can pull back a little on the throttle and cruise all day long at 2600 RPM or any slower speed with your low oil pressure or hi water temperature condition. Here's the description of SLOW mode from the gt40 manual It does nothing to give you an appreciation for what it feels like in the drivers seat. The video doesn't give a real good appreciation, you have to experience it yourself. Anybody with a gt40 should put their engine into SLOW mode and go for a ride to feel it for themselves It just takes a little jumper wire with alligator clips on both ends and you connect one end to the high temperature switch terminal (or the oil pressure switch terminal) and the other to a good ground on the engine. No wires need to be disconnected from either switch. You start the engine and your check engine light will be on, now go for a ride. PSA..........no ECM's or any other engine parts were destroyed while doing this..........it'll tell you that your system works the way it should though And to get most everything into one thread, here's a link to Marty's gt40 sensors and switches thread with locations and wire colors shown in the pictures It's a tan/black wire from the oil switch that connects to a green wire at the temperature switch and the green wire then goes into the harness to go to 2 different spots. One is to the ECM and the other is to the Red dash light This was a 2000 SAN and everything location and color wise agrees with Marty's 98 SN pictures. link

Mpost Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: July-05-2018 Location: Monticello, MN Status: Offline Points: 330	Post Options Post Reply Quote Mpost Report Post Thanks(0) Quote Reply Posted: August-28-2023 at 9:08am
	Than you Ken, What a great Idea. How about a post and link to this in the Poor Man's GT40 Diagnosis
	84 SN Sold 98 SN Lund Pro V 1975 Alumacraft

MrMcD Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3750	Post Options Post Reply Quote MrMcD Report Post Thanks(0) Quote Reply Posted: August-28-2023 at 6:24pm
	Nice work Ken, I have felt it first hand, in January when the water and air were very cold, we were a mile or more from the launch and I was worried we would die before reaching the dock. Simple repair but at the time not wanting to paddle back it does make you pucker a bit. If I had seen the video first it would be no big deal.

Sounds of a gt40 in SLOW (limp) mode

Poor Man's GT40 Diagnosis

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