Honda Bf90 4 stroke alarms

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muzkrat

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My 90 is cranking and idling great. when I accelerate the alarm starts going off and motor looses power. I replaced the impeller and water circulation is good. Oil light is on and oil level is good. Kinda perplexed. Could it be a faulty sensor ? Motor will idle around at about 1100 rpms but when it hits 1200 the alarm goes off. Any ideas or suggestions ?
 
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hondam

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BF90 isnt enough information, need a year, model, or serial number. Mainly need to know if its carb or FI.
 
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tommarvin

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If you have a computer on your motor, borrow a laptop,buy the software and cable, and diagnose the problem and log all maintance. If not.

Is the alarm for overheating, or a RPM limit switch sensor that's bad Im guessing it's a bad sensor, or an electrical problem.
 
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muzkrat

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tommarvin said:
If you have a computer on your motor, borrow a laptop,buy the software and cable, and diagnose the problem and log all maintance. If not.

Is the alarm for overheating, or a RPM limit switch sensor that's bad Im guessing it's a bad sensor, or an electrical problem.
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I feel like it is a bad sensor. The overheat light is not coming on and the oil pressure light is on like its supposed to be. I took the thermastat out and run the engine with the same results. Seems like the overheat light would come on if the sensor is sending out a bad signal. kinda perplexed.
I am not an outboard engine expert so be patient with me. I can only share the info I have.
 
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tommarvin

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You can test the t-stat by putting it in a pan of cold water heat it up slowly,what temp does it open? Be sure to put it back in. check the motor easy oil, to much is as bad as not enough.

Do you have a motor computer or Honda service manual? Can you locate the alarm or sensor and test it?

If your sure it's not overheating, Oh you may have to much motor oil alarm check for that, motor oil level is correct, and the boat will run with the alarm going, try boating close to the ramp to diagnose the problem, find and test the sensor. Tell us what you find out.
 
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hondam

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Failed sensors are rare but not unheard of especially if the motor has been cooked. You can try unplugging the sensors one at a time when the alarm is going off which will help narrow it down. Check the temperature with an infrared thermometer and install a mechanical oil pressure gauge.
 
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tommarvin

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That's a great idea, just start unplugging the sensors one at a time to find it , then test it. This reminds me when the mechanic told me to pull spark plug wires one at a time, until you find the plugged injector.
 
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BWDDKBR

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muzkrat said:
I feel like it is a bad sensor. The overheat light is not coming on and the oil pressure light is on like its supposed to be. I took the thermastat out and run the engine with the same results. Seems like the overheat light would come on if the sensor is sending out a bad signal. kinda perplexed.
I am not an outboard engine expert so be patient with me. I can only share the info I have.
Click to expand...
I had the same symptoms and mine turned out to be a water separator alarm. I had to go thru the entire fuel system to remove all the water and replace the water separator.
 
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