1992 Johnson fast strike 150.. Alarm when key on.. limited to 2500 rpms.

[beatle]

Motor just had Carbs rebuilt by mechanic, impeller and water pump working fine with good water flow.. motor peeing good.
Motor starts and idles ok but when you try to get up on plane motor cuts out. I feel it is getting kicked into slow mode just not sure why.. Turn key on and alarm sounds, if I unplug the temp gauge wires on port side, the alarm quits.. Does that mean the sensor is Bad? Boat has not been run to have any heat?
I dug into wiring harness and there is no blocking diode to be found. I replaced all the fuel lines and have tried seafoam and a good decarb just to rule out.. other problems .. Any Ideas??

 

[jakedaawg]

If it runs fine with temp sensor unplugged and you're sure it's not overheating the temp sensor would be suspect.

with cold motor place dvom on ohms scale. Unplug sensor. Place one lead on clean engine block. Place other on temp sensor wire. If you get a low reading reading replace sensor.

 

[beatle]

So I tried grounding the temp sensor wires to see if horn would sound. Starboard side makes alarm go off but, the port side with two wires won't so I am assuming the sensor is bad.. I will try with the Ohms and see what I get.. Thanks.

 

[jakedaawg]

That's right, two wires, use the tan w/stripe wire to ohm.

 

[w2much]

I may be mistaken but I don't think your alarm / safe mode can operate correctly with out the blocking diode. Once a sensor sends a signal your horn should sound then SAFE mode. If there is no blocking diode the powerpack keeps receiving a signal and you stay in safe mode. I just replaced my diode and hopefully get to test it by running the motor tomorrow on a planned dorado hunt. The factory manual is really helpful on this issue as it contains test procedures for sensors, horn and the diode.
Anyway I looked all over to get a diode, needed it right away. I know I could have one sent to me OMC/BRP price about 18. I also know you can buy the same diode for about 50 cents. No more Radio Shack bummer. Had to go to the dealer and pay the 18 dollars for the kit. That night I ordered 100 of them for 5 dollars on ebay. Two days later as I am soldering in the new diode the Amazon truck pulls into my driveway with 100 I had ordered 2 days ag​​​​​o.LOL
There is a harness test for the alalarm system. It includes the diode test.
By the way when at the Evinrude dealership the owner said he never heard of this diode. He has owned the place for about 10 years. Purchased it with old inventory. I asked that he check old stock which he did. Came out with this old OMC kit and asked what it was for. I explained to this BRP master tech what the diode was for and why I was replacing mine.He said that he had never done it and that the proper way,the way he does it is to replace the entire harness. Go figure.
Good luck, I am pretty certain you need that diode.

 

[beatle]

I checked the circuit with Ohm meter and it was only 0.7 I am assuming that is crap. Ordered a replacement for the temp
sensor.

You are correct about needing the diode, I have been doing a bunch of reading on it, and I decided to get a new wiring harness because a few other wires were in poor shape.. So when I get the new harness. I will make sure that it is in the harness.. figured it was a good idea since it is a 1992- to change all those wires while I'm at it. If you don't mind send me the info on the diodes you ordered and I will order some extra.. I don't really know what to look for on electrical, it isn't my strong point.. Thanks for you time and suggestions.

 

[w2much]

1N5399 is the number of the diode used in the harness.

 

[beatle]

Awesome I will get some ordered so I can be done with that little problem.. Thanks so much for the help