BF150 Falling on its face

I have a 2010 BF150 BANJ 1304288 The motor will run over 13 miles a hour for 5 minutes or so and then fall to an Idle with a steady alarm and only the green light on. The alarm doesn't stop until you bring the throttle back to an idle. I can run the motor all day at 12 MPH without any problems but as soon as I get up to speed it will run for a few minutes and then fall off again. I have replaced the fuel filters, empty the water separator, replace external fuel filter/water separator. Also the bulb stays firm. The only issue I can see is that the on board water sensor wires corroded off. I use the boat 2x week and have run it this way for several months trying to find the issue. I have also replaced the t stats. Water pumps perfect out the pee tube with a strong flow.
thank you in advanced for any suggestions.
Mark

Just a thought..... Thinking you might narrow down some possibilities with an infra red thermometer. It will identify there is a heat issue if there is one, AND, big bonus here, where that problem is occurring, providing you with further info that might help track your issue down. You don't need anything too exotic. Some are very inexpensive and work plenty well enough for this purpose....

Hi,

Too bad your control console warning lights don't seem to be working. The "on board water sensor" you say the wires corroded to...is that the engine temperature sensor by any chance?

I too think that this may be overheat related. Or, a false warning coming because of a possible issue still related to those corroded sensor wires.

Even though you say the pee stream is good, that only tells you that the pump is moving some water. I've seen "great pee streams" on outboards that only have 1 or two impeller arms left in the pump. Not saying that's what the problem is but if the pump isn't pushing the volume it's supposed to, then the engine will likely overheat.

jgmo said:

Hi,

Too bad your control console warning lights don't seem to be working. The "on board water sensor" you say the wires corroded to...is that the engine temperature sensor by any chance?

I too think that this may be overheat related. Or, a false warning coming because of a possible issue still related to those corroded sensor wires.

Even though you say the pee stream is good, that only tells you that the pump is moving some water. I've seen "great pee streams" on outboards that only have 1 or two impeller arms left in the pump. Not saying that's what the problem is but if the pump isn't pushing the volume it's supposed to, then the engine will likely overheat.

Click to expand...

My lights work fine. They come on when I start the motor and the temp light has come on briefly in the past. Turn key off and on the light went away and the motor started right up. I have read that temp issues, the motor will slow down slowly. this motor shuts all fuel off except enough to idle until you bring it back to idle with the throttle and then will go again. Like I said in the description of the issue it will run at 12mph all day without an issue. 13 mph or more no good. thanks

Yes as you describe it that's the way it's SUPPOSED to work. But...
I am wondering about those wires you said were badly corroded. If they went to the temp sensor then something associated with them being damaged might explain what's happening. You may want to look look into that further because, if wires are damaged in another area, it could be "confusing" the ECU so to speak. A small change in power setting could set up a different harmonic vibration that could cause damaged wires to touch each other or ground. I don't know...just tossing ideas out for discussion.

Here's another one....
An alternator with faulty diodes can induce ac current into the electrical system. Too much ac current in a DC system can cause wierd things to happen. Unplugging the alternator and running the engine can sometimes tell you what you need to know.

How long has it been since you saw the waterpump or had it replaced?


What are you pushing with that outboard that top speed is 13mph?
Just curious.

jgmo said:

Yes as you describe it that's the way it's SUPPOSED to work. But...
I am wondering about those wires you said were badly corroded. If they went to the temp sensor then something associated with them being damaged might explain what's happening. You may want to look look into that further because, if wires are damaged in another area, it could be "confusing" the ECU so to speak. A small change in power setting could set up a different harmonic vibration that could cause damaged wires to touch each other or ground. I don't know...just tossing ideas out for discussion.

Here's another one....
An alternator with faulty diodes can induce ac current into the electrical system. Too much ac current in a DC system can cause wierd things to happen. Unplugging the alternator and running the engine can sometimes tell you what you need to know.

How long has it been since you saw the waterpump or had it replaced?


What are you pushing with that outboard that top speed is 13mph?
Just curious.

Click to expand...

Interesting idea about the alternator. The issue I can't figure out is that I run slow speed, no wake for about 20 minutes before hitting open water and it will run flat out for about 2 miles before falling on its face. After sitting for 90 or minutes I get about a 1/4 of a mile before it does. Water pump replaced last year. 13mph is the speed it will fall on its face. I can run at about 30mph at top, but I try to run at about 25mph.

Yeah the "ac ripple" in a charging system can sometimes cause dc circuits to misbehave if it is too high. All generators produce ac voltage that gets rectified to dc voltage output through diodes. So, it's normal to have a little ac ripple. But, if the ripple gets too high, then the dc components don't work well.

The ECU would be particularly susceptible to high ac ripple caused by one or more bad diodes in an alternator. While it's not likely that ripple is causing your particular problem it's still something to consider if no solution is jumping out at you.

You can check the amount of ripple in your charging system if you have a digital multimeter and if you can gain access to your alternator's BATT (output) terminal.

Just set your meter to AC.MILLIVOLTS and connect the positive lead to the alternator batt terminal and the negative lead to battery ground. With engine running, you should not get a reading higher than 100 millivolts (0.100vac). I personally like to see less than 50 millivolts (0.050vac) but the specifications for some systems have changed since I was doing these tests frequently and there is ongoing debate about what can be allowed.

Lots of info about alternator ac ripple testing on the net and it's a good thing for a DIY troubleshooter to know.

My money, for what it's worth, is still on a possible problem in your overheat warning circuitry but I am far, far away from being someone that gets it right all the time.

Just trying to help you brainstorm and work the problem.