25hp CDI bad? Help troubleshoot

[Mozella15]

I recently bought a used 2013 F25LA with trim/tilt, electric start. It had a cheap non-Yamaha throttle so I installed a Yamaha 703 control box with a Pro series analog tach. I disconnected the engine mounted warning lights and plugged in the 6y5 83653 Trim/Oil harness which I connected to the tach in accordance to the wiring diagram. Everything works except the oil and water warning lights. Neither will come on. I didn't test the water sensor but I did conform that the low oil pressure sender goes to ground with the engine off and shows open with the engine running. That is, I believer normal.

When I disconnect the Trim/Oil harness at the engine and ground the oil signal wire or the water signal wire (with the ignition key on) the lights illuminate properly. The wire from the oil pressure sender goes through the CDI unit before connecting to the Trim/Oil harness and the water over-temp sender wire does the same.

Based on my testing and limited experience I think that the warning lights are designed so that they will not illuminate unless the engine is both running AND the oil pressure is low, or if the water temp is high. In other words, they are not supposed to illuminate by simply turning on the ignition. That tells me the part labeled CDI has some aspects of an ECU even though this engine is rather simple with a carburetor
.
The fact that the oil sensor (and I'm guessing the water temp sensor too) tests good and grounding the signal wires down stream from the CDI hints that the tiny little brain inside the CDI that determines when these lights come on is malfunctioning. In other words, upstream (engine side) of the CDI, everything tests OK and downstream of the CDI (steering console side) the lights test OK.
But I hate to replace the CDI just on a hunch since it costs North of three hundred bucks.

Can anyone conform that my troubleshooting logic is sound, or is there another reason that the warning lights don't function properly. I should mention that even though the engine was made in 2013, the appearance inside the cowling is spotless and looks factory fresh.

I should also mention that I disconnected my recently added equipment and reconnected the factory (engine mounted) warning lights. They don't work either.
Help please.

[panasonic]

I am pretty sure your logic is correct. The CDI is also referred to as a microcomputer on your engine. It gets signals from your oil pressure sensor and temperature sensor and if a fault is detected it will put the engine in RPM reduction mode (2500rpm) and the warning light on the engine. I do not think there is anything wrong with the CDI/microcomputer on your engine. There is a test in the service manual for these warnings.

I do not know if you can make these lights work on your gauges. Hopefully Fairdeal or Boscoe will chime in and help you with that.

[Mozella15]

I am pretty sure your logic is correct. ......... snip.................................... I do not think there is anything wrong with the CDI/microcomputer on your engine............. snip....................

I'm a bit confused. My diagnosis leads me to believe the wiring is good, the warning lights illuminate when tested directly, and the low oil pressure sender is working properly. Unless there is a broken wire hidden deep somewhere in the engine harness, the only other component in the circuit is the CDI. My thinking is that it must be bad, yet you say you don't think there is anything wrong with it. If the CDI is OK, where would you suggest I look for the fault?

[boscoe99]

What fault are you looking for?

[Mozella15]

What fault are you looking for?

I'm not actually looking for a fault. I found that. I'm trying to solve the problem that the low oil pressure light won't illuminate with the engine running when I ground the signal wire from the oil pressure sender.

[panasonic]

I went back and read your original post and see what saying now. You do not think that with the key on, when you ground the oil pressure switch WITHOUT the engine running, the light should come on....correct?

I thought the same thing. My experience with these small F 9.9, F15 and F25 is exactly how they work. But all that I have worked on were manual start engines, so no battery or key switch. The only way to know if the warning system works is to test them while the engine is running, ground the selected switch, warning light comes on and engine goes into RPM reduction mode.

So perhaps the electric start models with a key switch works differently...I don't know.

I don't have the service manual for your exact model but I will see what I can find out.

Also I was pointing out what is listed in the parts as a CDI is a little more than that. But it seems you have figured that out.

Do you have the correct manual for your Engine?

Sorry if I confused you.

[Mozella15]

I went back and read your original post and see what saying now. You do not think that with the key on, when you ground the oil pressure switch WITHOUT the engine running, the light should come on....correct?

I thought the same thing. My experience with these small F 9.9, F15 and F25 is exactly how they work. But all that I have worked on were manual start engines, so no battery or key switch. The only way to know if the warning system works is to test them while the engine is running, ground the selected switch, warning light comes on and engine goes into RPM reduction mode.

So perhaps the electric start models with a key switch works differently...I don't know.

I don't have the service manual for your exact model but I will see what I can find out.

Also I was pointing out what is listed in the parts as a CDI is a little more than that. But it seems you have figured that out.

Do you have the correct manual for your Engine?

Sorry if I confused you.

Back in the day, car low oil pressure switches connected to "idiot lights" turned the warning light on anytime the oil pressure was low; i.e. with the key on but before the engine was started. These days, ECU's are smart enough to turn on ALL the dash lights for a few seconds as a light check, and then, typically, most of them go out they and only illuminate again when a certain condition exists when it's not supposed to exist. In other words, the oil pressure is SUPPOSED to be low when the engine is off; therefore, the ECU is NOT going to show you a warning light at that time since nothing is actually wrong.

This "smart" kind of operation is good for the person with no understanding of how an engine works. I suppose Chevrolet and Ford got tired of people saying, "I'm afraid to start my new car because it has no oil pressure". Perhaps that's one reason they made ECUs which are smarter than their customers. But the smarter machines in my life are harder for a guy like me with nothing more than a multi meter to troubleshoot. Even my coffee maker has a fancy "brain" inside of it................. sigh.

I"m pretty sure my Yamaha 25hp works the same way as modern cars. The low oil pressure warning light is not shown when the engine is not running and as I understand it, that's the way Yamaha intends for it to work. But, as you say, when it IS running and if the oil pressure is low (or when I ground the oil pressure signal wire) the light should illuminate and the engine should go into "limp" mode. It doesn't do that.

Since I have confidence that the ordinary wiring and ordinary light bulbs are all working OK, I have strong suspicions that my CDI is bad. Of course, to me it's a "mystery box". Who knows what's inside and what it's supposed to do.

I have never had oil pressure problems with a Yamaha 4 stroke, but I have used the low oil level warning on 2 stroke models. A couple of times I have been thankful the overheat warning system was working when the water intake became clogged with debris and the warning sounded. Clearing the blockage was an easy fix. However, if the overheat warning system is inoperative, the first indication of trouble might be a big plume of smoke or some horrible sounds associated with the rods knocking. OUCH!

That's what I'm trying to avoid and that's why I'm on the verge of replacing the CDI in spite of the more than three hundred dollar priced tag. Unless someone can tell me a different reason the warning light system doesn't work, that's what I'm seriously considering. I don't want to buzz around in my boat without any protection against oil or temperature problems.

And no, I don't have the correct manual for my engine, but that's on my shopping list too.

Thanks for your input.

[boscoe99]

I am not yet sensing that there is a fault within the motor.

Disconnect the tachometer lights and reconnect the LED light assembly that is part of the motor. Then retest. Let us know what you see.

The tachometer lights (incandescent ~ 12 volt bulbs) typically have 12 volt power applied to them.From the key switch. The CDI or ECU applies the ground.

The smaller motors that use an LED assembly for visual warning are not provided with 12 volt power. The get their voltage from the CDI. Nominally a volt or so I would imagine since that is about all that an LED can withstand. I don't think the CDI has the muscle to illuminate incandescent bulbs contained within the tachometer.
zled.jpg

[panasonic]

"The low oil pressure warning light is not shown when the engine is not running and as I understand it, that's the way Yamaha intends for it to work. But, as you say, when it IS running and if the oil pressure is low (or when I ground the oil pressure signal wire) the light should illuminate and the engine should go into "limp" mode. It doesn't do that."



Again I do not have your exact engine manual, so this may be different. But I believe there are times involved in the tests for the warning lights and yours will be similar. This is from an older F20 manual.

You really need the proper manual for your engine.

F20 warning.JPG

[boscoe99]

Again I do not have your exact engine manual, so this may be different. But I believe there are times involved in the tests for the warning lights and yours will be similar. This is from an older F20 manual.

You really need the proper manual for your engine. Shirley, you jest?

Below is the test procedure for the OP's model. But it is testing just the warning lights.

OP is trying to illuminate 12 volt incandescent bulbs in lieu the lamps that are designed for use with his model.
zled12.jpg

[boscoe99]

[QUOTE=panasonic;n225831]

You really need the proper manual for your engine.

How have you been? How is your carrier doing? Crazy what has become of the aeroline industry.

[panasonic]

[QUOTE=boscoe99;n225835]

You really need the proper manual for your engine.

How have you been? How is your carrier doing? Crazy what has become of the aeroline industry.

Crazy is right. I been on off duty status for almost 2 months now. Just a skeleton crew still working to carry out storage checks on all the aircraft parked.

We are running about 30% of normal Sked flights right now and the pax loads are still low....so not good at all.

I am returning to work in August along with a limited number of others to do some catch up work to keep some of the aircraft from calendaring out. Meaning the maintenance has to be done no matter if the aircraft fly or not. Don't know how long this work will last. People don't want to get on airplanes right now and there is really no where to go to any way.

Tough times.

[Mozella15]

Thanks for the schematics and troubleshooting tips. I tested both on-engine warning lights with a AA battery and they both illuminate. Then I connected them up as it came from the factory, ran the engine, and grounded the signal wires. Previously I simply touched the wire(s) to ground not anticipating that there might be a delay built in to the logic circuit. This time I held it to ground well past the recommended 10 seconds........... NOTHING.
Just to be clear, I'm not trying to drive the bulbs in the tach unit using the power from the engine-mounted LED warning lights. As mentioned earlier in this thread, that is not likely to work because of voltage considerations.

It's important to realize that the lamps in the tach get power from an "ignition on" wire inside the steering console similar to my fuel gauge. All they need to illuminate is a ground on the appropriate signal wire in the Trim and Oil Lead harness. The warning lights are supposed to illuminate when the sensor goes to ground. Connecting the signal wire directly to ground on the tach side of the CDI makes the lamps light, but when passing through the CDI, I get no joy; just like the engine-mounted warning lights.

So, if the CDI is able to supply a ground to the LEDs when detecting a low oil pressure condition it makes sense to me that it would also provide a ground to my tach mounted light bulbs. At the moment, as far as I can tell, the CDI is failing to do this part of it's job.

For the oil pressure warning light, the ground wire is P.W. That corresponds to the G/R wire in the Trim-and-Oil lead which is the ground for the tach oil warning light. So far so good.

But oddly enough, the ground for the engine mounted overheat LED on the engine is P/B which does NOT connect to the Gy ground wire which activates the Tach mounted light bulbs. It matches with the G wire. However, it would be easy enough to swap the Gy with the G wire and make the tach mounted lights function assuming the CDI will take these signal wires to ground with low oil pressure and/or high water temperature.

The fact that the engine mounted LEDs illuminate with a AA battery but will NOT function when performing the test suggested by boscoe99 strengthens my believe that there is something wrong with my CDI. Arguments to the contrary welcome.

A search of the internet turned up several sources for the F25 service manual, but the ones I could peek at didn't have any electrical troubleshooting procedures. I hate to buy the wrong manual. Can anyone point me to the correct service manual so I can find information like that LED test procedure posted by boscoe99?

By the way, am I the only person in the world who thinks that connecting a Yamaha branded tach to the F25 is a good idea? Surely someone has tried this before.

Thanks again for all the responses.

[panasonic]

For the manual P/N, see the list of topics on this forum. The very first one is in Yellow...a sticky, "Yamaha Service Manuals Part Numbers" by Boat.net. They sell the manuals on this site I believe. OR go to Yamaha publications website.

The manual is about $80 and is worth every penny. On that Yamaha site you can "rent" manual as an Ebook for like $ 15 for 30 days.

The way I look at is...we shell out many thousands of dollars for engines, but when it comes to spending a $100 dollars or so on a service manual that shows everything repair and maintain your engine, we balk at the price!!! It's a common theme on this site and others.

[panasonic]

Just to be certain, you did exactly what is in the service instructions I posted? Engine RPM at least 2000 and grounded the" wire harness side."
I have to ask because it is another common theme here to give people instructions, they come back and say they didn't work, only to find out later that the instructions were not followed correctly.

I am sure others have put a tach on a small engine and wanted these lights to work. I remember a guy on here rigging out a LED light up on his dash for oil pressure. He had the same trouble as you I think, it would not light a incandescent bulb...I think.

The regulars on here are doubtful about CDI and ECU failures because they rarely fail. Many people end up with spare ones in the end.