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Honda BF100 oil pressure light problem

L

leachs4

New member
Can any one provide me any advice on my honda BF100 outboard.
When you first start the engine the oil pressure light is bright green but after a minuite or so the light fades out. As i dont want to run the engine with the light out i would like to find out whats wrong.

The problem started when i was running the engine when the light went out, i checked the oil and it was low so topped it up and every since then there has been a problem. I had never had a problem before this the light was always bright.

I have check the oil level and that is ok I have removed the oil pressure switch with the engine running and oil comes out , i have check the switch and this appears to be ok.

As the light comes on when i first start the engine could this be a problem with the pump or filter ??

thanks

steve
 
Funny, I looked in the book to give you a pressure reading for the OP switch and I couldn't find a specification. The book says to do just what you did...remove the switch, start the engine and see that oil comes out of the hole. How 'bout THAT! Very scientific.

However, I would want to know what the pressure is so I agree with justintime although I have never rigged a gauge to a BF100.

I do work on later model BF 8 and 20 D engines and the minimum spec for those is 21.3 psi at 900 rpm. Not sure if that would apply to the earlier engines but it sounds reasonable.

The thing to be concerned about though is that the switch itself closes at a much lower pressure than that as it is meant to indicate LOW or NO pressure when it stops glowing. I believe that it takes less than 10 psi to close that switch so knowing that you have good pressure to prevent engine damage can only be absolutely verified with a gauge.

If you haven't drained and re-filled the crankcase with fresh 10w40 oil, do that and see if the light stays on. Even if it does, it would be best to get an oil pressure reading if only for your peace of mind.
 
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Looking at the wiring diagram, it looks like the light is a neon bulb. It gets its power from the ignition. Once you determine that there is oil pressure (like Jimmy, I have no idea what it should be), if you ground the lead going to the pressure switch and run the engine, the light should light.

If it does not stay lit, then it can be the light losing its "stuff", bad connection, or a problem in the CDI.

If it does stay lit and you have pressure, I would change the pressure switch.

Mike
 
Thanks for the info. I have reread the service manual and i will try to borrow a pressure guage to check but either way i think i will replace the oil filter and check the pump is clean as i have not had the engine long and am concerned it may be bunged up.

Thanks
 
Just getting ready to take the engine out to get at the oil filter on the service manual P118 it refers to the Concealed bolt can any give me any pointers on finding this bolt as the rest of the instructions i am happy with its just this one diagram i am not happy with.

thanks
 
There are eight bolts total. The four "exterior" bolts that hold the case extension are obvious. Once the case extension is off, there are three bolt in a sort of a triangle pattern at the front under "cavity" of the case. At the rear of the case, The "hidden" bolt head can be seen just ahead of the exhaust pipe after you remove the exhaust pipe seal. A long extension with a "wobble" end makes getting it out pretty easy.

One other tip:
If the power head doesn't separate easily from the oil case because someone has glued the gasket, do not tap on the sides of the oil case, not even with a soft faced mallet. The case sides are fairly fragile and will crack unexpectedly. I learned this one the hard way. Since then, I've run across a couple that had plenty of Bondo work that looks like the same thing happened before.

Hope this was clear enough. Good luck,
jimmyd
 
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thanks for that Jimmy, it was most helpfull. I have dismantled the engine this morning and rebuilt it, still no light but the engine is happier i dont know how but it starts better and runs better (it might be that i am imagining)

Going to get a replacement oil pressure switch now that i know the internals are clean.

Steve
 
Finally sorted my issue, in the end i replaced all oil parts, filter / check valve and spring / oil pressure switch and lamp.

After a rebuild i know have a nice bright green light. I did test the old bulb and this was ok so i assume i was mostly the oil pressure switch but changing the other parts i know they are all ok.

thanks to all that help me through this.
 
I'm new to this forum so first of all just wanna say hello to everybody. I'm also new to outboard motors as well and have never worked on them. I've just bought a BF100 and although it runs well the oil pressure light will not illuminate at all. I've taken it out and tried it on a battery but it did not light up. Is this the correct way to test it or is there another way? There is plenty of oil in the engine but I don't want to damage the engine by running it with no oil pressure.
Any help is greatly appreciated. Also its an silver engine, can anyone tell me roughly what year this may be from?

Thanks

Ian
 
Hi PINKFLOYD,
Hello and welcome aboard.
I'm not sure if hooking the oil light to the battery is the definitive test. It should work but I'm not positive. My wiring diagram shows the exciter coil voltage, which is alternating current, going through a diode which should rectify the voltage to 1/2 phase DC.

I have some of these that I could try and test but I can't get to them at the moment. I'll try and answer in a couple of days if no one else here gets back to you. In the meantime, please know that the lamp only indicates TOO LOW or NO oil pressure and only an oil pressure gauge will tell you what is really happening. No one seems to know what the pressure should be but I believe that it should at least be over 15 psi to prevent engine damage.

Your engine being silver would say to me that it is a 90's engine. But, to be sure, post your serial number off of the swivel tube and maybe Hondadude can look it up for you.
 
Like Jimmy said...post the serial number. It will make a difference in the light if it has points or if it has a cdi. If it has a cdi then one of my previous posts will apply....."Looking at the wiring diagram, it looks like the light is a neon bulb. It gets its power from the ignition. Once you determine that there is oil pressure (like Jimmy, I have no idea what it should be), if you ground the lead going to the pressure switch and run the engine, the light should light.

If it does not stay lit, then it can be the light losing its "stuff", bad connection, or a problem in the CDI.

If it does stay lit and you have pressure, I would change the pressure switch."

Mike

..
 
Thanks for the info guys, the swivel tube has what looks like a plate riveted on but the numbers were stuck on by somebody, I took them off expecting to find numbers stamped on the plate but there were none. I did make a note of the numbers so hopefully it'll tell me what year the engine is

The numbers are 1013022.

This engine seems a bit too much of a gamble to take my 2 young kids to sea with so its going back on ebay as I've now bought a new BF8.

Thanks for any info guys.

Ian
 
If the number is correct, it is a 1978. Model number is BF100. I know the motor is being passed on...but for the record and for discussion purposes...the serial number indicates that the motor has points. There is a separate part of the ignitor coil under the flywheel that exclusively provides voltage to the light bulb. The bulb is lighted by the ac voltage from the coil through the oil pressure switch to ground.

Looking over your previous posts

Testing the bulb with a 12v battery should light it.
Just to verify that it truly is the serial number that I looked up...if you can remove the bulb as just a little bulb only (with no leads), it is the one with points. You can either used an ohmmeter to check continuity or a 12v battery to light it. Polarity does not matter.

You probably just have a bad bulb. Its rating is 12v 3.4w. See part # 13 http://www.boats.net/parts/search/Honda/Outboard%20Engine/0/BF100%20LA%20VIN%23%20BF100-1000001%20TO%20BF100-1020309/SHIFT%20SHAFT%20%2B%20CARRYING%20HANDLE%20%2B%20COVER%20LOCK%20LEVER/parts.html

If this is not the bulb, we are going down the wrong track...

Mike
 
If the number is correct, it is a 1978. Model number is BF100. I know the motor is being passed on...but for the record and for discussion purposes...the serial number indicates that the motor has points. There is a separate part of the ignitor coil under the flywheel that exclusively provides voltage to the light bulb. The bulb is lighted by the ac voltage from the coil through the oil pressure switch to ground.

Looking over your previous posts

Testing the bulb with a 12v battery should light it.
Just to verify that it truly is the serial number that I looked up...if you can remove the bulb as just a little bulb only (with no leads), it is the one with points. You can either used an ohmmeter to check continuity or a 12v battery to light it. Polarity does not matter.

You probably just have a bad bulb. Its rating is 12v 3.4w. See part # 13 http://www.boats.net/parts/search/H...CARRYING HANDLE + COVER LOCK LEVER/parts.html

If this is not the bulb, we are going down the wrong track...

Mike
 
Thanks

The number is definitely correct as I've looked on the engine and its stamped on there and looks original.

I don't think the engine is that old though as it does have a CDI unit fitted next to the carb on the RH side.

Also the engine has been repainted silver at some time but its also silver inside the leg which would be difficult to paint without stripping the entire engine, so I think it was probably always silver.

Also the oil pressure warning light is a sealed unit with the wire attached and wouldn't ya know it has now started working and shines bright green when the engine is running.

Thanks

Ian.
 
Glad you got it working. I must admit...the serial number has me baffled. Were there no letters in front of the number?

Now I am back to the original info on the bulb. It is a neon light and you can not test it with a battery. So, what you have said is consistant with your testing.

Hopefully, it was just a bad connection.



Mike
 
Can anyone describe how to disassemble the oil pressure light socket or lens removal, so I can replace the light bulb inside (34903-259-000) the motor is a Honda 1983 BF100 (9.9hp) perhaps someone knows as I tried however I don’t want to damage it. Thank you
 
Hi,
Do you have the serial number for your outboard? It was located on the stbd. side of the swivel case on a "stuck on" name plate. Many have been removed or fallen off by now though.

The reason I ask is that, as far as I know, only the earliest models of 7.5hp and 10hp used the oil lamp with a replaceable bulb.

Subsequent serial numbers of those, as well as the 9.9hp designated models, used a lamp that is sealed and has to be replaced as an assembly. If you do attempt to pull one of the assemblies (part# 37210-ZV4-003) apart it will likely ruin it.

All of the sealed assemblies install from the outside of the case by pushing in until the seal "lip" locks it in place.

The seal for the replaceable bulb assembly also installs from outside the case but the housing engages the seal from inside the case. If you remove the housing from the seal and lens by pulling it inward, the replaceable bulb will be exposed.


Also, my info has the part number for the 3.4 watt bulb replacement as 34902-259-000.

I hope this helps you.

Good luck.
 
Flippinjigs,
I just wanted to add that, in many cases I've read about here concerning the green oil light not working, it often turns out that nothing is wrong with the lamp itself. Often it can be the switch or the wiring that is the cause. Make sure you keep that in mind as you sort through your problem.
Good luck.
 
jgmo said:
Hi,
Do you have the serial number for your outboard? It was located on the stbd. side of the swivel case on a "stuck on" name plate. Many have been removed or fallen off by now though.

The reason I ask is that, as far as I know, only the earliest models of 7.5hp and 10hp used the oil lamp with a replaceable bulb.

Subsequent serial numbers of those, as well as the 9.9hp designated models, used a lamp that is sealed and has to be replaced as an assembly. If you do attempt to pull one of the assemblies (part# 37210-ZV4-003) apart it will likely ruin it.

All of the sealed assemblies install from the outside of the case by pushing in until the seal "lip" locks it in place.

The seal for the replaceable bulb assembly also installs from outside the case but the housing engages the seal from inside the case. If you remove the housing from the seal and lens by pulling it inward, the replaceable bulb will be exposed.


Also, my info has the part number for the 3.4 watt bulb replacement as 34902-259-000.

I hope this helps you.

Good luck.
Click to expand...

SN B100S-1502830 I have the lamp part number indicated above.
 
My Serial Number is B100S-1502830. I have a replacement bulb with the same part number you described above. Trying to understand how to get the bulb out of the socket
 
Well, the Honda service manual lists THREE different lamp assemblies.
The one with the replaceable bulb is for engine serial number 1000004 to 1199999

Then comes serial # 1200001‐1299999 with sealed lamp

After that is serial # 1300001 and subsequent that uses a slightly different sealed lamp with a small "window" that directs the light upwards.

So, if your outboard has the earlier bulb assembly I guess my Honda factory info is wrong or someone has substituted it along the way.

I listed the bulb part number simply because I noticed that the number you listed was one number off of what is available and I didn't want you ordering the wrong part by mistake. The number you listed was
34903-xxx-xxx while I listed 34902-xxx-xxx.

If you do indeed have the replaceable bulb lamp assembly, it should separate from the rubber weather grommet from inside the case while the grommet and green lens remains attached to the outside of the case. Once separated, the bulb is easily twisted out of the socket unless there's corrosion.

But, again, any effort to disassemble either of the subsequent sealed assemblies will likely ruin them and they are $34 ++.

Good luck.
 
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