2003 Johnson 150 port temp sensor

[D_J_Winn]

I have a 2003 Johnson 150 thats going into slow mode after about 15 minutes of running 3/4 of throttle. No alarms, no lights ever displayed on tack. When I disconnect the port side temp sensor/quick start, I can run without it going into slow mode. All temps are 145ish when it’s going into slow mode (temp gun).
Water pump was replaced in the beginning of the season, has a strong stream, t stats have been confirmed and they r opening. what else would case me to go into slow mode besides that switch, and is there anything else I should check before I bit the bullet on an expensive used part? any help would be appreciated. Thanks

 

[saltchuckmatt]

I have a 2003 Johnson 150 thats going into slow mode after about 15 minutes of running 3/4 of throttle. No alarms, no lights ever displayed on tack. When I disconnect the port side temp sensor/quick start, I can run without it going into slow mode. All temps are 145ish when it’s going into slow mode (temp gun).
Water pump was replaced in the beginning of the season, has a strong stream, t stats have been confirmed and they r opening. what else would case me to go into slow mode besides that switch, and is there anything else I should check before I bit the bullet on an expensive used part? any help would be appreciated. Thanks

Expensive used part? Seems like you've isolated it, buy a new sensor. Better check into why your tach didn't let you know.

 

[D_J_Winn]

Expensive used part? Seems like you've isolated it, buy a new sensor. Better check into why your tach didn't let you know.

Yes, that part is discontinued and people who have them know it….I think that is my concern. All lights come on and horn prior to start up. So I feel comfortable saying they all work. I also double checked by grounding temp wire to see if the light come on and they do. Just a little confused as to why it’s putting me into slow mode without an alarm.

 

[saltchuckmatt]

Yes, that part is discontinued and people who have them know it….I think that is my concern. All lights come on and horn prior to start up. So I feel comfortable saying they all work. I also double checked by grounding temp wire to see if the light come on and they do. Just a little confused as to why it’s putting me into slow mode without an alarm.

I didn't have your model number but it's your year and your hp. Need to check model for sure. I was told BRP was still making and supplying parts. Anyhow, marine engine.com

 

[racerone]

Sorry , but he needs the one from port side !---The 2 switches are different.

 

[saltchuckmatt]

Sorry , but he needs the one from port side !---The 2 switches are different.

Race, the parts breakdown that I looked at doesn't differentiate from port and starboard. Just says temp sensor. Where do you see that or are you just pulling our legs?

 

[flyingscott]

On the parts fiche for a johnson 150 #s 15 and 20 are the sensors

 

[saltchuckmatt]

On the parts fiche for a johnson 150 #s 15 and 20 are the sensors

Wow, I went to parts first where is just list the sensors and doesn't differentiate from either side. But when you go to parts breakdown and then individual parts you get the description. That sucks! I wonder how many people have gotten screwed on that one. Also, one would think a temp sensor would be the same on either side.

 

[flyingscott]

One is a standard temp sensor. The 2 wire one controls the SLOW operation with the second wire.

 

[saltchuckmatt]

One is a standard temp sensor. The 2 wire one controls the SLOW operation with the second wire.

Yes, and NASA had a sq. Co2 scrubber filter on the command module and a round one one lunar module. Engineers!

I did learn you could get the 585203 off another engine and change the pigtail but those are gone to. Only ones I found were $300 something used on eBay. Revenge of the Ficht I guess!

 

[Chris1956]

The 2 wire temp sensor also controls the Quickstart function, which advances the timing until the motor warms up.

The fact that you do not get a temp alarm is worrying.

 

[Chris1956]

You might intentionally ground one of your overheat sensors and see if you get the overheat alarm. If no alarm, maybe the diode in the wiring harness is open?

 

[D_J_Winn]

You might intentionally ground one of your overheat sensors and see if you get the overheat alarm. If no alarm, maybe the diode in the wiring harness is open?

Good idea, I’ll double check that. Thanks

 

[flyingscott]

If the diode was open I believe the horn would sound all the time. I think the diode is there to isolate the VRO signal.

 

[Chris1956]

If the diode was open, I do not think the alarm would "see" the ground signal.

The diode is between the two overheat sensors plus the connection to the powerpack to signal SLOW, and the alarm sensor. The other alarms have their own signal wires.