Engine Problem

We were heading out of the channel a couple of days ago when I got an alarm. It was 2 short beeps. Then maybe a 30 second pause, and then 2 beeps again. Oil pressure and engine temp gauges read fine for both engines. I had checked the oil, transmission and coolant levels before going out.

I opened the engine compartment to find light smoke which quickly cleared. Climbing down I could not see any ongoing source of smoke. However, the starboard drive/shaft was noisy. So, we immediately shut down the starboard engine and headed back to the dock on one engine.

I looked over the starboard engine carefully and couldn't see any obvious problem. The hoses and belts looked fine. I carefully felt the temperature of each hose and compared between engines to see if there was any obvious difference (I know, not very scientific). The belt looked ok. I felt the transmission to see if it felt hot, and it was barely warm.

So, I tried to restart the engine to further diagnose, but it would not start. It seemed like it wanted to start but just wouldn't keep running. I recalled that I did have a couple of stalls on the starboard engine at idle speed a couple of months ago, but fine since. So I'm thinking that the shaft noise that I heard may have been due to the engine misfiring, but it was not obvious.

I called a mechanic who immediately said that I must have overheated the engine and likely caused engine damage, but that doesn't make sense considering the temperature gauge was reading normal. A new water pump was installed about a year ago. Mechanic is coming out to diagnose later in the week.

I have gasoline engines on a fresh water lake. They are MerCruiser 8.1 HO.

So, wondering if anyone has ideas on what might be the problem or anything that I could check. Does the 2 beeps mean anything vs a continuous alarm?
Just trying to prepare for talking with the mechanic. The smoke was obviously the most disturbing part of this. Appreciate any thoughts.

What year mercruisers and what does the manual say?

A wild thought

How old are your risers? Mercruiser recommends a 5 year changeout. A failed riser can put water into the wrong place leading to a spot overheat (not seen at gauge) or hydro lock. Did you check your oil for any off color?

Meridians came with ECM equipped engines- have the codes pulled to narrow down the faults.

It is probably a “beep code” that will lead you to a general problem. You need to get the manual and look up the beep code.

So I went to Google and typed in Mercruiser Beep Codes. Heres what came up:

Signal: Two beeps every minute
Possible Cause: Sensors / Open-Short in circuits
Corrective Action: Connect CDS to determine and diagnose the problem
Engine Usage available for user: Possible 90% available power (dependent on sensor). See dealer for diagnostics.

Looks like you will need to call a Mercruiser Tech.

Thank you all!! You prompted me to go back and search the manual. Duh! I've lost faith in the manual because it's a thin little book that's never helped me before, but.....it says that 2 beeps indicates a sensor fault. Could that have caused something to smoke? I'd love to think this is merely replacing a sensor, but that seems to easy. And, I guess that I will need a professional mechanic with a diagnostic tool.

It's possible the wiring to a sensor chafed and shorted, which could have caused the smoke as well as a bad sensor reading that upset the ECU.

Frank60 said:

Thank you all!! You prompted me to go back and search the manual. Duh! I've lost faith in the manual because it's a thin little book that's never helped me before, but.....it says that 2 beeps indicates a sensor fault. Could that have caused something to smoke? I'd love to think this is merely replacing a sensor, but that seems to easy. And, I guess that I will need a professional mechanic with a diagnostic tool.

Click to expand...

The mechanic will (should) have a computer to hook up to the engine and it will most likely have a more detailed fault that will take him/her to the problem. Good luck.

Code readers for cars are fairly universal,perhaps one of the auto units can be plugged into the read out socket on your engine?

FF said:

Code readers for cars are fairly universal,perhaps one of the auto units can be plugged into the read out socket on your engine?

Click to expand...

Mercury/Mercruiser has VesselView, which can display fault codes- but the vessel must have the VesselView hardware. Otherwise, they use a specific plug and reader to pull codes.

rslifkin said:

It's possible the wiring to a sensor chafed and shorted, which could have caused the smoke as well as a bad sensor reading that upset the ECU.

Click to expand...

Chafed wires are actually a common issue on Mercruiser 8.1s. Check the wiring runs on the inboard side of the exhaust elbows.

FF said:

Code readers for cars are fairly universal,perhaps one of the auto units can be plugged into the read out socket on your engine?

Click to expand...

You need a special tool because marine engines don't use OBDII ECMs . I have a Tech Mate that works great on MEFI and ECM 555 based engines like Volvo Penta and Mercruiser use. They cost about $500, if memory serves.

Do not ever use this mechanic

Frank60 said:

We were heading out of the channel a couple of days ago when I got an alarm. It was 2 short beeps. Then maybe a 30 second pause, and then 2 beeps again. Oil pressure and engine temp gauges read fine for both engines. I had checked the oil, transmission and coolant levels before going out.

I opened the engine compartment to find light smoke which quickly cleared. Climbing down I could not see any ongoing source of smoke. However, the starboard drive/shaft was noisy. So, we immediately shut down the starboard engine and headed back to the dock on one engine.

I looked over the starboard engine carefully and couldn't see any obvious problem. The hoses and belts looked fine. I carefully felt the temperature of each hose and compared between engines to see if there was any obvious difference (I know, not very scientific). The belt looked ok. I felt the transmission to see if it felt hot, and it was barely warm.

So, I tried to restart the engine to further diagnose, but it would not start. It seemed like it wanted to start but just wouldn't keep running. I recalled that I did have a couple of stalls on the starboard engine at idle speed a couple of months ago, but fine since. So I'm thinking that the shaft noise that I heard may have been due to the engine misfiring, but it was not obvious.

I called a mechanic who immediately said that I must have overheated the engine and likely caused engine damage, but that doesn't make sense considering the temperature gauge was reading normal. A new water pump was installed about a year ago. Mechanic is coming out to diagnose later in the week.

I have gasoline engines on a fresh water lake. They are MerCruiser 8.1 HO.

So, wondering if anyone has ideas on what might be the problem or anything that I could check. Does the 2 beeps mean anything vs a continuous alarm?
Just trying to prepare for talking with the mechanic. The smoke was obviously the most disturbing part of this. Appreciate any thoughts.

Click to expand...

No way he understands that engines are cooked, without looking.

Gordon

I just got towed back to the launch ramp 2 days ago in my 17 footer with a 90 Mercury Optimax. It was also giving the 2 beep code.
I couldn't find anything on line or in the manual for a 2 beep. But a friend found something that also said it was one of the sensors and would have to get plugged into diagnostic software to figure out which sensor.
It's at the shop now, when I know more I'll update.

Run it, break it, fix it, repeat

I'd one occurrence with a Mercruiser where the beeps occurred and the engine went into limp mode. Bad plug connection in the harness. The mechanic said the fault indicator showed an overheat indicating a bad riser. Risers OK, plug not ok.

Two years ago we were cruising with some friends. The JD 6081 fault sensors put the engine into limp mode due to overheat. Indications according to JD book leaned towards a bad sensor. Oh oh, coolant level way down due to leak in keel cooler hose. Added all reserve coolant diluted way down with fresh water to top up system. Made it 55 nm to Petersburg where hose replacement took place.

Long story short, sometimes beeps are right.

Find a certified Mercruiser mechanic with Rinda scan tool.

Frank60 said:

We were heading out of the channel a couple of days ago when I got an alarm. It was 2 short beeps. Then maybe a 30 second pause, and then 2 beeps again. Oil pressure and engine temp gauges read fine for both engines. I had checked the oil, transmission and coolant levels before going out.

I opened the engine compartment to find light smoke which quickly cleared. Climbing down I could not see any ongoing source of smoke. However, the starboard drive/shaft was noisy. So, we immediately shut down the starboard engine and headed back to the dock on one engine.

I looked over the starboard engine carefully and couldn't see any obvious problem. The hoses and belts looked fine. I carefully felt the temperature of each hose and compared between engines to see if there was any obvious difference (I know, not very scientific). The belt looked ok. I felt the transmission to see if it felt hot, and it was barely warm.

So, I tried to restart the engine to further diagnose, but it would not start. It seemed like it wanted to start but just wouldn't keep running. I recalled that I did have a couple of stalls on the starboard engine at idle speed a couple of months ago, but fine since. So I'm thinking that the shaft noise that I heard may have been due to the engine misfiring, but it was not obvious.

I called a mechanic who immediately said that I must have overheated the engine and likely caused engine damage, but that doesn't make sense considering the temperature gauge was reading normal. A new water pump was installed about a year ago. Mechanic is coming out to diagnose later in the week.

I have gasoline engines on a fresh water lake. They are MerCruiser 8.1 HO.

So, wondering if anyone has ideas on what might be the problem or anything that I could check. Does the 2 beeps mean anything vs a continuous alarm?
Just trying to prepare for talking with the mechanic. The smoke was obviously the most disturbing part of this. Appreciate any thoughts.

Click to expand...

A quick search on Google found this link. There are plenty of posts about Merc Cruiser gas engines.
https://www.offshoreonly.com/forums/general-q/354365-mercury-optimax-fault-codes.html

Please post back when you do find and fix the problem. It will help others.

Damn! I'm so glad we have two great condition, carburated, 1977, 350 cid/255 hp Mercruisers; turning 71c Velvet Drive BWs that lead to 3 blade props. Engines hit recommended 5,450 rpm during [very lightly loaded] momentary WOT test [23 +/- knots]. At 1,900 rpm she cruises a relatively economical 6 knots [7.58 knots is calced hull speed]; 2.5 +/- gallons per hour. Simple is as simple does!!

Planing at 16 to 17 knots she uses 16 to 20 gph, depending on load. At the slower speed of 6 knots, when we do or do not tow our small runabout, the fuel usage seems no noticeable alteration.

Best luck with the beeps, boops from... as well as various diagnostic equipment needed for newer engines.

Update

The MarineMax mechanic is coming tomorrow. The first mechanic that I called didn't tell me until a week later that he didn't have the diagnostic tool and that I needed to call someone else. So wasted a week. I'll post back the final resolution. I did carefully look over the engine visually, and I don't see anything obvious. I pulled the flame arrestor, and there did appear to be some black soot. So maybe I had a backfire/misfire that caused the smoke. Really hoping this is just a sensor replacement. I know it's wishful thinking.

So, a quick update and the saga continues. MarineMax came out a couple of days ago and used the diagnostic tool on the engine. They said that I was having a multiple cylinder misfire and that the IAC was running at almost 100% duty cycle...or something like that. They were going to replace the IAC, but the mechanic thinks that may not be the issue. He thinks it's my plugs.

About 6 months ago, I replaced my plugs using the plugs and gap specified in the Service Manual (AC Platinum 41-983, gap 0.060). This particular mechanic has taken issue with me using the AC Delco plugs ever since I installed them even though that's what the manual specifies. He says they're crap and that I should have used NGK plugs. As near as I can tell, the engines have been running fine for the last 5 months.

More importantly, he's telling me that the 0.060 gap in the manual is a 'well known' misprint, and that the correct gap is 0.045. Before I incur the expense of the IAC replacement, he is suggesting that I replace all of the plugs with NGK and a 0.045 gap. I can't find anything online to substantiate that there's a misprint in the manual. Every reference that I find says the same thing, AC Delco Platinum 41-983 with a 0.060 gap.

I was wondering if anyone was familiar with the MerCruiser 8.1L (496) engine and has heard about this 'misprint'.

I sure don't want to go through the trouble of changing 16 plugs unnecessarily and possibly gapping them wrong on top of that. He's not trying to get me to pay him to do the job. He even loaned me a couple of tools to do it myself. He seemed very sure of himself on the 0.045 gap.

The IAC is at 100% because the engine runs so rough due to the misfire. I seriously doubt replacing the IAC (Idle Air Control) will have any effect.
As far as spark plug gap a narrow plug gaps burn excessive fuel better leading to less plug fouling while a wider plug gap can foul easier and requires a higher ignition coil voltage. The trade off is in higher RPM engine performance. The engine manufacturer tests the engine and its systems for maximum performance at all RPM ranges. Run a narrow gap and you may find you have other performance issues.


If the manual has "A well know misprint" ask the mechanic to show you some reprinted page or bulletin that shows the correct gap.



Several other forums about Mercrusier mention the plug type to use. Some of these engines came with Denso plugs and while others used NGK or AC Delco.

AC Platinum 41-983, gap 0.060 is the preferred plug for this engine as per several other forums. I really think its user preference. Maybe this mechanic had a bad experience with AC plugs and decided to use NGK.

I would question the 0.045 gap though. I don't think the engine will perform properly.

When I've gotten information that I either don't trust or is contradictory to what I believe to be true, I ask several others with knowledge on the subject for their professional opinion. Call several other boat repair shops. Avoid talking to the "front counter". Call some smaller shops where you are talking to the guy that actually maintains boats. But call 2 or 3. You will get a consensus on what spark plug to use and what gap should be.
As a business consultant I tell my clients I will never tell them anything I can't prove using other sources.


The bigger issue is why are the plugs fouling. A leaking fuel injector(s), faulty fuel pressure regulator, a weak ignition coil or even a couple of bad spark plug wires can cause source of the problem. Once you correct the misfire, run the engine(s) to see if the problem comes back. If so you fixed the symptom but not the cause.

.045" gap is normal on older Mercruiser engines. I would use the recommended .060" on the 8.1 unless you changed to MSD ignition instead of the stock stuff. Swap coils from one engine to the other and see if the problem follows the coil. I cannot recall all the details, but have you ruled out water in the fuel?

Have you contacted Mercury corporate support? I don’t have Mercury engines but they must have some kind of phone support for issues like this. Ask them about the well known misprint and see if they know about it. Also if MarineMax replaces the part and it doesn’t fix the problem are they willing to reinstall the original part and not charge you for the unneeded part?

I would pull a plug or two from the misbehaving engine just to have a look.
If they are clean and grayish to light brown that means those cylinders are firing ok.

Do your engines have HEI distributers? The ones with the coil built into the cap?

Confirmed Plug Gap

I spoke with Mercury Marine and a couple of other mechanics and confirmed that I have the right plugs and properly gapped. Not that that's settled, we can go back to looking for the cause. Waiting for MarineMax to come back to continue diagnostics and/or replace the IAC. On the lake here it seems that everyone is backed up two or three weeks for service. That's painful when the weather is so nice, and I'm stuck at the dock. Thank you for everyone's input.

KnotYet said:

I would pull a plug or two from the misbehaving engine just to have a look.
If they are clean and grayish to light brown that means those cylinders are firing ok.

Do your engines have HEI distributers? The ones with the coil built into the cap?

Click to expand...

My engines are fuel injected. There is an individual ignition coil at each cylinder.