Bass 150 kicks back to low RPM at will

[sheddercrab]

I have a 1996 DT 150 S High Performance model with EFI

Great engine acting up. Here's the summary:

Runs fine and after a bit it throttles way down out of no where. Does not stall but you can smell gas when this happens. Feels as if you hit a sand bar or just yanked the throttle from 4k RPM all the way back to idle in gear.

Once it does this it will not go over 2k rpm or so. Shut it off and it will start and idle like a gem. Has SNAP ........ you mechanics know what I mean there.

We changed ALL filters and installed 12 new NGK plugs. Took it out tonight for a test run and it ran great for 15 minutes ............. then did the same dang thing. New fuel line and primer bulb. Gas is crystal clear clean.

It is almost like it is doing it on purpose. I heard they do something similar if they overheat or get low on oil? It never does this straight out of the shoot either, but will do it every trip.

No alarms and oil level is ok. Never stalls and will always run slowly back to the ramp.

Hope you can help me out as I can smell the Stripers coming down the Jersey Coast. I really need one

[Solarman]

dt150,, 96, running issues

If bulb is not collapsed when this happens, then I would start by checking the low pressure fuel pumps. Specifically looking at diaphragms, and the 2 clear plastic discs (check valves), in each of your pumps (2). The check valves have been known to break into pieces. They can not be replaced without replacing the pump, so if good don't disturb them.
Let us know if you find anything.

[sheddercrab]

update

We have narrowed it down to an ignition issue. Little or spark on starboard bank. Plugs are wet with gas.

Now it just runs at low RPM (2,000) all the time. We replaced the magneto with another one and it still does the same thing.

Plugs are wet with gas and we are the CDI unit at this point. Getting frustrated. Any ideas welcome.

Dan

[lovebugsall]

DF 115 OUtboard - Electrical Problem

My DF 115 outboard electrical help

Battery is fully charged
Had trouble on water. Would not crank. Inigition and gauges functioning. Cleaned up connections no help. Noticed cable fraying a (+) connection. Cut and striped wire back but still looked rusted. Tired to wrap and reconnect no go. Friend then said try to switch (+) & (-) cables did it before I could stop him. After that inigition and gauges went dead. I can get new power cables but do not know about the inigition and gauges not functioning. Is there a fuse/CB???

3 hour tow back to dock!!

Sorry I added to your thread could not figure out how to add new post to this forum help please.

[sheddercrab]

dt150,, 96, running issues

Just put it all back together and both banks are firing like crazy ...... snappy as ever ............ won't last though as we did nothing of consequence.

Intermittent ............... any way to test CDI when it acts up again ?

[Solarman]

dt150, 96, running issues

Your CDI (condenser discharge ignition) is common to all 6 cylinders, if getting good fire on one bank, I might be thinking something for that side of motor. If no codes on monitor, I would still check all sensors for that bank, pulse coils, or wiring connections to the primary coils for those cylinders, if it is intermittent. Plug boots/ wires might be shorting at higher RPMs?
Check your manual wiring schematic to see if any other switches are common to that side of motor.
Let us know what you find, it might help others. Good luck.

[sheddercrab]

Sequence of operation

Solarman ............ first of all, Thank You for your time.

Is this sequence of operation correct .........

1. Stator coil/AKA the charge coil
2. Pulser coil/AKA trigger coil
3. CDI box
4. Ignition coil
5. Keyswitch and emergency stop switch.
6. The flywheel itself


The flywheel spins and magnets inside of the flywheel along with the charge and pulser coils make electricity for the CDI box. On the charge coil wires, it will make 100+ volts, of the pulser coils just a couple of volts. The charge coil charges up the capacitor inside of the CDI box. Then when the engine is supposed to fire, the pulser coil tells the CDI box to discharge the stored voltage inside of the capacitor, and the CDI box dumps that voltage into the ignition coil. The ignition coil in turn steps up that voltage from 100+ volts to the 20 to 30K volts needed for the engine to run. The process repeats itself 1000's of times over and over as the engine runs.

Now when you want to shut off of the engine. Either with the keyswitch if you have one (or the stop button, these models come both in remote start and pull start). What it does is it grounds out the white wire coming out of the CDI box, and the voltage that is supposed to go to the capacitors shorts to ground, the ignition system stops firing, and the the engine stops running.
So it is a combination of the charge coil and the pulser coils that you need to look at next. If the CDI box gets no charge voltage, or gets no trigger voltage from the pulser coils, it will not fire the coils.

[Solarman]

dt150, EFI, running issues

The gear counting coil, ECM, and tps are also part of the picture.
If the CDI is firing for one bank, why wouldn't it fire the other side.
You also have a low speed charge coil, AND a high speed charge coil on the magneto. They are the two different coils on the magneto near starter.
You changed the magneto, and unless the high speed charge coil is bad on both my thoughts would be to check the pulse coils, gear counting coil (must be proper distance from teeth to read each tooth - gives ECM speed of crankshaft). Pulser coils give exact position of crankshaft and tell ECM to fire the specific coil, and the tps adjust the timing according to the throttle position.
The pulse coils also need to be proper distance from flywheel (if yours are adjustable) to send a good signal to the ECM & CDI.
Likewise, your primary plug coils have to have clean and good connections.
The rest of your list seems good. Sensors do wire into the ECM, but generally flash a code if bad. Just make sure the connections are good.
Good luck, tell us how it's going.