TOPIC: Red light on!

So yesterday we had a little boat outing in the Puget Sound. Long story short, I made it 5 miles out and suddenly got a flickering to steady red light on the controls and then the horn. I backed off the throttle and looked back to see normal water pump pressure and didn't hear anything unusual and quickly shut her down.

I was running around 20 knots, so not quite WOT but close. I pulled the cowling and did a visual inspection, nothing unusual. I looked for any obstruction/debris, nothing. I decided to gamble and start it up. It idled fine and pumped water fine. It didn't seem hot. I decided to float about for about 20-30 mins to let things "cool" down if it was in fact hot.

I checked the oil and nothing came up on the dipstick
I hadn't noticed any leaking and there was no sign off oil out of the exhaust. So after letting it sit I checked again, nothing but residual. So I added a quart and checked it again, this time it showed. So maybe I was about a quart low. Ok.

Started up, no problems except I still had the red light. I decided to limp back to the marina.

When I got home I drained the oil and put fresh oil in. I looked over everything and nothing jumped out at me saying "I'm the problem!"

I admit, I'm not an engine guy. I can do the routine tune up stuff but after that...nope. Unfortunately a great engine mechanic and friend of mine that worked on this F Block passed away earlier this year. He is missed for sure.

Thoughts?

It's a 1970 but with a '65 cowling.

Have you started when cold to see if the light is on? If so could be the sensor in the manifold has gone bad. Should be able to check that with an ohm meter. Has the block ever been descaled? Could be rust has broke loose and is causing a restriction. I use an infrared thermometer to check temps on the block and manifold to look for hot spots.

Just reread your post. A quart low and running close to WOT is not a good thing, you only had a quart circulating though the engine. Low point on the dipstick is 1 pt. Warning light and horn also alerts you of low oil pressure. So this may not be an over heating issue but an oil pressure issue. I would pull all the plugs, remove the oil sending unit and put a manual gauge in it's place then crank it over to check what pressure you have. If the pressure is good the sending unit may have gone south. This too can be checked with an ohm meter.
These engines do use some oil and it's best to check them before each outing.

Thanks for the reply. After changing the oil I put the boat in our lake and ran it. No light at first, then it came back on.

I haven't descaled the outboard, I have to look into how to do so. As far as running low on oil, I had no idea how they did on oil consumption. Everything I've read never really indicated high oil consumption and is kinda misleading when there's no smoke

I'm on the water now and the light didn't come until ten minutes into low power settings. Earlier I cleaned the p-hole <tell tail> and have a solid stream coming out. The stream flickered a few times at idle but was otherwise okay. I don't have a temp gun but there's not any sign of overheating.

In the owners manual it states that it is normal if the red light comes on at idle after the engine oil is warm. Meaning if the engine oil is warm the viscosity is lower than when cold, and it is possible at idle speed for the oil pressure to be so low that the sender closes thus allowing the red light to illuminate. If you raise the rpm to say 1000 rpm the light should go out. If it does not go out at elevated rpm then that indicates a problem. The problem can be in the warning light circuit or the engine itself. What weight oil are you running?

The warning light circuit basically consists of a light with 12vdc on one side of the bulb, and the other side of light gets grounded by either the oil pressure sender near the filter or the temp sender in the exh elbow. The oil pressure sender is a switch that is normally closed, it opens with oil pressure. That's why the light is on if you turn ignition on but don't start the engine. Once started, the oil pressure should open the switch thus shutting off the light. So, light on = closed oil pressure switch= low oil pressure. Light off = open oil press sw = normal oil pressure.
THe temp sender is normally open when cold, closes with elevated temperature, thus illuminating the warning light.

Thanks for the info. Ron had me running straight 30w oil. Currently I'm running 10-30w. I'm doing some more test today. I'll check the switches but my concern is there's a rise in either pressure or temp when running. If the light isn't on when I first put the boat in the water, then comes on around 10 mins into it (happened now twice) wouldn't that suggest either a temp or pressure problem? I'm not second guessing and won't rule out anything, I really do hope it's a switch.

I pulled the wires off of the oil pressure switch and had continuity. I started the outboard with the wires disconnected and still had continuity. I'm going to try and find a switch...

Kelly wrote:

Thanks for the info. Ron had me running straight 30w oil. Currently I'm running 10-30w. I'm doing some more test today. I'll check the switches but my concern is there's a rise in either pressure or temp when running. If the light isn't on when I first put the boat in the water, then comes on around 10 mins into it (happened now twice) wouldn't that suggest either a temp or pressure problem? I'm not second guessing and won't rule out anything, I really do hope it's a switch.

I run straight 30w in all of mine, Delo 400, an oil with enough zinc for wear protection. Ask Helmar about Delo 400. You'll have a rise in temp or a DROP in oil pressure that triggers the red light. Personally I would put a gauge in place of the sender and insulate the sender connection, run it and see if the light comes back on and if so see what kind of pressure it has. If the light does come back on it will be a cooling issue as the oil sender is disconnected. If the light stays out and oil pressure is good I'd say the oil sender is defective. They say it takes 7 lbs of pressure to float a bearing, meaning you have a cushion of oil between the metal surfaces, under 7 lbs you are metal to metal contact. I don't know what the sender pressure is set at, I'll see if I can check one of mine. You need to isolate which one of the senders is setting off the light so you can address which system needs troubleshooting.

Check out the pictures of my first Bearcat tear down, look at the rust scale built up in the water jacket. This is what we mean by descaling the block. www.classicboatclub.com/showthread.php/857-Bearcat-1-Teardown

Thanks again for your assist. I don't have a gauge to put in place of the switch, do you have a part # for a gauge so I can find one? Local parts store?
I'm also looking for a part # for a oil press. switch...do you have that easily available?

I've looked all over for a pressure switch part number, no luck. Ron had installed a new one when he was building my Cat, but I have no idea where he got it.
Anyone know what a suitable substitute part number is?

The gauge I used was intended for air but works fine. I'll have to get at one of mine to see what pitch thread, it's either 1/8 NPT or 1/4 NPT. Not sure which direction to point you to find one. Bill or Ed may have the sender, if we knew for sure the activation pressure something I'm sure could be found in auto parts store. I'll see what I can dig up within the next day or so.

I believe you are right Dick, most sending units for "idiot lights" are set to come on at or below 8 psi if I'm not mistaken.

Excellent advice on the oil pressure gauge, and most line kits (for hooking the gauge up) have several different thread adapters in the kit. Available at and auto parts store for $25-$45. You can also pickup a "T" to run the gauge and the light at the same time if you'd like, I think that would be my preference.

PS - Please pardon my butting in here, too much coffee I guess!

Thanks guys, and by all means anyone and everyone is welcome in this thread =)

I have misplaced my Bearcat manual since we moved last summer. I thought maybe it would have the exact oil pressure range for the switch. Everything I could find here and a few other forums the range was pretty large, 10-40 psi. The parts stores had several lower range switches but I wanted to be exact. Do I only need to worry about the minimum?

Interesting note. I pulled the switch to take to the parts store and when I came back empty handed I decided to wipe it out, re-install it, and give it a whirl. When I first started the Cat the light was on immediately. I decided to go put it on the trailer and halfway back to the ramp the light went off (3 mins of run time). So I decided to try different throttle settings and see what happens. I got up to about 3/4 throttle and backed off and the light came back on and stayed on. Hmmm....

Went out to the garage and pulled two senders, they are 1/8 NPT thread. Tested them the best I could as the air compressor guage is vague down that low. My best guess is one switch activated at 8lbs and the other slightly higher at 10lbs. I also noticed I had two wires on the sender so if you disconnect the sender those two wire need to be hooked to together so the temp sender will still work.

Kelly you still need to isolate which problem is causing the light to come on. If it's oil related you can be doing some serious damage by running it. That's not to say overheating won't cause damage either but it's the lesser of two evils. Myself I'd be trying to locate a gauge. You can see the one I have mounted in this video:
You can't read it but when I start it it's 25 to 30 lbs and when I rev it I get 45 to 50 lbs. Don't ask me where I got the gauge as it's been as round for over 50 years!

One thing you could try without having a gauge, disconnect the two wires from the oil sender, connect them together with a third wire, on the end of the third wire attach an alligator clip. Hook the clip to the sender. Now when you run it if the light is on you can unhook the clip from the sender. Light out you have an oil pressure problem, light still on heating problem. That way I or others can help with the root of "the" problem and not two different problems causing the light to come on.

MarkS feel free to butt in anytime!

Good stuff, thanks for posting. I did the wire test yesterday with the light (sorry forgot to mention) and it's definitely oil pressure related...whether it's actually oil flow or indication is what I'm trying to now figure out. Do you have a manual that shows a pressure range?

Good deal now we can proceed with diagnosing the causes.
Just checked the manual and it says a minimum of 15 lbs at 700 rpm and 30 lbs at 5000 rpm. That would mean the light should be on at 14 lbs and under. So if you can some how get 15 lbs on the switch and it's open, it should be good. I threaded an air fitting on my sender, turned the regulator to zero on my compressor and slowly dial it up with an ohm meter hooked up, watched where it closed and at what pressure which appeared to be between 8 to 10 lbs. I couldn't find anything to ID the senders except one had a name: Cole-Boston USA.

Well I'm fearing the worst right now. I pulled the press. switch and put air to it with a meter attached...open. Closed without air. Ugh.

I checked the oil level and well that was ugly. It had the viscosity of water. Cracked block? Something else?

Was it milky colored or just really thin? Are you running the original mechanical fuel pump?

Funny you say that. It was milky when I changed it out. Kinda suspected water then but wasn't certain about what is what with this outboard. 20/20 look back says duh, that wasn't good. This time it wasn't milky, just watery.
I'm 99% sure it's a mech. fuel pump.

Having slept on the idea I'm now wondering if it's really a cracked block since the oil wasn't milky this time...maybe a bad seal? I don't really know, I'm just throwing darts.

Has the oil level increased? Reason I'm asking I'm wondering if the diaphragm in the fuel pump has gone bad and it's pumping fuel into the oil.

It was high yesterday when I checked it. In fact, quite a bit high. Strange if it was a fuel pump issue,wouldn't the level have been high when I checked out on the sound?
Would a malfunctioning fuel pump cause a red light...indirectly?

Well for now I'm concentrating on what you have going on now. The milky oil has not returned after you changed it but you have very thin oil and a high level which is indicating a bad diaphragm. To properly diagnose the problem you really need to get a gauge. It's a little strange that it takes a while till the light comes on. It could have a sticking relief valve. The sender could be sticking. Just hard to say but a gauge will give us more insight.

www.steinertractor.com/FDS405-oil-pressure-gauge?utm_source=msn&utm_medium=cpc&utm_campaign= [roi]+pla&utm_content=all+products

www.amazon.com/s/180-6240125-6644167?ie=UTF8&field-keywords=oil%20pressure%20gauge&index=blended&link_code=qs&sourceid=Mozilla-search&tag=mozilla-20

Manual says a simple way to check for any oil pressure is slowly unscrew the sending unit with motor running. Oil should squirt out. Also might check for a stuck relief valve in the adapter housing.
Water in the oil is about as scary as it can get. I assume you know it's not gas which would indicate a bad mechanical fuel pump diaphragm. I would check for water in the lower unit also just because.
Best of luck,
Steve
WizardIII

I think you guys are on the right track. I noticed when I checked the oil that the first few drips on a paper towel spread like a spider crack, indicating fuel. I didn't smell it at the time but it's starting to make sense.
With fuel in the oil, the viscosity would be breaking down causing pressure to decrease even though there's a lot of fluid. Make sense? If it sits overnight, the fuel would have a chance to sit on top of the oil. Once started, it would take some time to mix up and thin out, thus a delay in the light coming on.

So last night I pulled the dipstick again and more "oil" came out. It didn't smell like fuel but after the discussion here and with Bill yesterday it seems highly probable the fuel pump is no bueno. I'll get a oil pressure gauge today along with some new Delo400 oil and a fuel pump in a day or two. I'm optimistic at this point...

I really appreciate the information and help!

There was a slight delay in troubleshooting since I had family in town visiting.
I installed a new fuel pump and changed the oil and filter. I put Delo 400 and a new Napa filter. Gave everything another once over and dropped it in our lake. It ran fine for the first 10 mins again, then light on. When I pulled the boat out my dad noticed the entire shaft area was extremely hot to the touch. I don't ever remember that being the case, even after running all day. I had good water pressure out the telltale again. Could this be a thermostat issue?
I'm still waiting on the gauge to come in the mail. I should have it by Tuesday. I also have to order the pressure switch just to have it. I'm going back outside to dig around a little more. Maybe even pull the starter and see if there's a lot of scale in there.

Does anyone think that maybe the oil pump has gone south? And I'm still curious about why you were a quart low in your original post.
Steve

I'm still waiting on the gauge to get here. Today if I get the opportunity I'll remove the pressure switch with it running to see if any oil comes out. That should tell me if the oil pump is working right?

I'll stick with the gauge test as the next step. If you loosen the sender while running it may still have pressure below what the switch needs to close and leak out or if the sender is bad it's going to leak, is this going to tell you what the pressure actually is? For piece of mind you need to know what the pressure is. Yes the oil pump could be bad, relief valve weak/sticking, or excessive bearing clearances. Who knows for sure until you have pressure readings.

Not sure how hot the leg will get. It's dumping hot water and exhaust into it, I've never paid any attention to the heat here.

Just seems like 'slightly loosening' the sender would at least tell if the pump was working at all. Cleaning the relief valve also seems like a quick fix and while you're waiting.....why not?
A gauge is always a good idea, I have an old one for mine. Actually I'm thinking of mounting it inside the engine compartment since it has a 'flexible' hose on it.

Finally got the gauge! Installed and yep...40 psi. Pulled the side plate off and looked for scale, almost non-existent. Cleaned what was there with a dental pick, modified screwdriver and vacuum. The screwdriver was mod'd in a way that I could get under #1 and in front of it as well, scraped and cleaned...all good.

Good water, good oil, left the gauge in, re-connected the wires and no issues running. Good oil pressure at all throttle settings, good water pressure.

Ordering a new switch soon.

FYI:

Best of luck,
WizardIII

Great News! Now after checking these items you can have peace of mind.

Thanks for all of your help! All of this will go in the memory bank to help the next person...

Glad to have helped, got to keep the old beasts going!!!!