Please help! Mercury issues, on vacation

Guys I could really use some help here on our yearly vacation and my Merc is giving me trouble. I just bought the boat last week it has a 2008 Merc 115 four stroke on it. I am getting a constant beep after the engine has ran for 10-15 minutes. Will act up within a few minutes if I run it wide open. The impeller is a year old and I’m getting a good stream out of the telltale. I checked the oil it was overfill by about a quart maybe a little less, I let some out until it read good on the stick, tried running it again, same thing. I can put my hand on the cylinder head and it’s warm but not hot. Please help!! Save our family vacation!! Thanks in advance to any input

I’m no expert, but I did say at a holiday inn express last night.

I think I’ve heard the the thermocouple itself has been known to go bad. That would mean that your motor is not running hot, but definitely not enbough confidence to simply ignore it or unhook it.

Would there be any kind of alarm for engine oil level?

I can’t really think of anything else. I really hate that feeling when I’m on vacation. Been there many times with my last boat trailer and its crappy bearings.

The way I understand it is low oil or an overheat alarm will be a series of 4 or 6 beeps. But I have a constant tone. Thanks biggill for your input!

Iowaboy seems to be our forum/resident expert on these kind of things. Hopefully he sees your “flare”. He knows his stuff…!

If you look, there’s still a thread here where another member was having an issue…”Merc 40 4-stroke overheating?”. Maybe not the exact same issue, but certainly some similarities. Hopefully iowaboy1 sees this.

Check your float in the oil reservoir that’s under the cowl, attached to the motor head if your model has one.
Sometimes they stick. Also, if you have that reservoir on the motor, see if the tank isn’t completely full. If not, open the cap about 1/2 way, start the motor, (lower end in the water) and let it run in idle mode and hopefully the tank starts to fill with oil again. Once it does, screw the cap back on tight. Hopefully your good to go.
Let us know if that works.

a constant alarm can be one of two things,either it is something with oil level,or the module that the sensors communicate with has failed,easy way to find out.

first,find the wire from the oil level sensor,unhook it,does alarm quit now??
if so,the float is stuck,or the sensor itself is bad which is very common.

still got the alarm??? leave the oil level sensor unhooked,now,unplug the temp sensor,it should be a single wire sensor up near the top of the motor pointing to the rear of the motor,unhook it,alarm gone now?? if so,temp sensor has failed.another very common failure.

if you still have an alarm,and its constant,I would be willing to bet the module has failed,common issue also.
to ease your fears,is the oil level changing indicating it IS using oil as intended??
these things are pretty easy on oil so it may take a bit to notice the level changing.

if it eases your mind even further,mix your two stroke oil 50 to 1 as if it were an older model,dont worry,the worst you could do is foul a plug if the injection system is working properly.

to shut the alarm off if every thing checks out,pm me,I will tell you how to do it,wont post it on public forum.
the best advice I can give you is to get it to a merc dealer asap,would really hate to see you burn the old girl up.
best of luck!!!!!!! and I hope your vacation is a great one!!!

Thank you Iowaboy for your input! But it seems like you’re describing a 2 stroke, correct me if I’m wrong, but mine is a 4 stroke. Any ideas on that?

dang it!! I must be more tired than I thought,in rereading your post I see that it is a four stroke,constant alarm is oil pressure!!

okay,different approach needed,so sorry,find the oil pressure sensor switch,unhook and ground the connector,does the alarm quit now??
if so,one of two things is going on here,the sensor is bad,or the motor has very low or no oil pressure.
the only thing you can do now is have the pressure checked with a mechanical gauge,if it checks out,a new sensor is in order.
without being there to check it out for myself,I cant be of much more help.
find a dealer or reputable outboard mechanic asap.

one more thought,if you have changed the oil before your trip,the alarm may have set because it did not sense pressure right away and the computer has it in memory,unhook the battery cables,both of them,now hook the cable ends together,( this will drain the capacitors that act as small batteries )
should take about five minutes.

reconnect the battery and see if it the alarm quits now.
sorry for my earlier stupidity.

one thing not mentioned was that his oil was over full. if the motor is running in “choke” mode and dumping in a lot of extra gas you will lose oil pressure that way. did the oil you drained out have a strong gas odor? might be best to change the oil. if the thermostat isn’t working and the motor is running cold could cause this, common merc issue but more so on the verados.

I have a merc 2 stroke and when I had a solid alarm it was a water pump issue ! I found the alarm codes by searching google

Thanks everybody! I’m going to see a Merc dealer this morning.

Tom,let all of us know what you find out,there are so many problems that can occur with outboards and someone will have an issue like yours.
posting what is found out may help someone else out if and when a similar thing happens to them.

there are a lot of good people here that would in a second be there to help you if it were possible to do so.
best of luck!!!!

Went to the Merc dealer today. They hooked it up to their laptop and everything looked good to them, no codes to be found. Just to eliminate some parts I put new spark plugs and fuel filters in, but that didn’t help. Still having the same problem, pretty much out of ideas at this point.

if I had it here and you are still fighting an issue,we would take it to the lake and get it to act up,then one at a time,start unhooking sensors until the beeping quit.
once it was discovered which sensor was causing the problem,that one would get replaced,or even possibly the module that the sensors are hooked to is bad.
at this point I would be willing to bet the temp sensor is bad,it wont set a code and will be intermittent.
I am willing to bet the reason the dealer couldnt find anything is that they run it on a hose while testing it and simply did not get it warm enough to trigger an overly sensitive temp sending unit.

if you have the time and funds,once the problem is found,I would install a water pressure gauge and a temperature gauge on the dash,more stuff to contend with I know,but at least you can ‘see’ whats going on.

Steve Fellegy has a merc tech he has recommended highly here in the past,send him a pm and see if he will give you his number.

Tom Anderson wrote:

Went to the Merc dealer today. They hooked it up to their laptop and everything looked good to them, no codes to be found. Just to eliminate some parts I put new spark plugs and fuel filters in, but that didn’t help. Still having the same problem, pretty much out of ideas at this point.

So the Merc tech said no “history” of any alarms? Never heard of that….any and all past alarms should show up–even if the alarm was NOT going off when the tech and the “test”/computer check was in progress. Something fishy with this Merc tech/test/computer check? ALL alarm history should show up–long after the alarm went off and which one it was and for how long etc. Near as I know. Am I wrong?

What area are you in/on vacation?

Fault Codes: Most late-model outboards record every instance that the motor generated a warning horn or a fault code. These would include over-revving the motor, over-heating, and over-charging the battery. Frequent instances of over-revving could indicate an abusive owner, or one who’s been running too small a prop.

“The Verado motors even record the over-rev data in stages,” explained Dan Jansen, a certified Mercury technician at Mr. Marine (www.mrmarineinc.com) in Fond du Lac, Wis. “It will show me if the motor was over-revved in neutral, just bumping the rev limited in gear, or what it calls abusive over-rev in several stages, which means someone was really hammering on it.”

In the case of an over-heat warning, the Mercury computer will record the date it happened, and also the duration of the over-heat incident.

“It might show that the motor over-heated for 80 seconds, which means the owner noticed the warning and responded right away,” said Jansen. “But if I see it was overheated for 8,000 seconds, that means the owner ran all the way home with the motor hot. And that could mean trouble down the road if he didn’t get it fixed correctly.”

The engine computer may also check systems, such as fuel pressure, water pressure, charging, and the function of fuel injectors, all basic diagnostics that a technician would use to quickly pinpoint a problem.

“A Mercury Optimax actually sounds OK on five cylinders,” said Jansen. “It will just be down on power at full throttle. I can get a really good picture of how each system is working from the computer.”

Each outboard manufacturer also has a system for tracking the history of each outboard it has sold. With Mercury Mercnet, for example, a dealer can see the motor’s ownership history, the occurrence of any warranty claims, whether the motor has a remanufactured powerhead, and whether it is up to date on any recalls or service bulletins.

I am in the Hayward Wisconsin area. The mechanic that looked at it also said that it certainly should have stored a trouble code but for whatever reason it didn’t. I talked to another Mercury tech while searching for parts and he said if the spark plugs and fuel filters didn’t take care of it the next step is to take it out on the water with the laptop hooked up to it. They closed yesterday at 2 and not open on Sunday. So I guess I’ll go see them first thing in the morning. The more I mess with it the more I’m leaning toward a fuel pressure issue. My theory is the fuel pump is making enough pressure/volume at low rpm but not enough at high rpm. Of coarse my fuel pressure gauge is at home.

Thank you everyone for your help!

Tom Anderson wrote:

I am in the Hayward Wisconsin area. The mechanic that looked at it also said that it certainly should have stored a trouble code but for whatever reason it didn’t. I talked to another Mercury tech while searching for parts and he said if the spark plugs and fuel filters didn’t take care of it the next step is to take it out on the water with the laptop hooked up to it. They closed yesterday at 2 and not open on Sunday. So I guess I’ll go see them first thing in the morning. The more I mess with it the more I’m leaning toward a fuel pressure issue. My theory is the fuel pump is making enough pressure/volume at low rpm but not enough at high rpm. Of coarse my fuel pressure gauge is at home.

And there might a low pressure fuel pump and a high pressure fuel pump. I dunno on that model…but many do have both.

Just never heard of any alarms/alarm history not showing up on a computer check/read out…wow. Good luck…

Got the motor fixed today, ended up going to a different mechanic that apparently has an actual Merc scan tool. The first shop must have used a more generic scan tool. The problem ended up being the fuel hose going from the rear of the boat to the motor. It was deteriorated inside the hose which ended up plugging the fuel filters and wrecking the lift pump. If you’re ever in the Hayward area and need a Merc shop I highly recommend Johns Marine. I brought the boat to them at 8:30 this morning and had it back by 3:00, I should also mention they had the boat in and out of the water 4 times to finally find the problem. They also dropped the motor one hole because on their test drive they noticed that the prop would blow out too soon. I eventually need a different prop but I have to let the funds rebuild a little before that. Thanks everyone for your help, I still managed to salvage most of our vacation. Thanks again guys! Time for me to go put a bend in a rod!

glad you got it fixed and it certainly speaks volumes for the value of a GOOD mechanic.
The deterioration has me thinking there was an awful lot of ethanol run through that motor. Hopefully you try and purchase non oxygenated fuel whenever possible.

Good to hear Tom! With hopes the rest of your vacation is flawless…

I doubt Merc would approve of a “Merc Tech”/Merc dealer NOT using the right scanning device to diagnose Merc issues. They ( Merc) need to know…just sayin’!

I only put 91 non-oxy in everything except my truck. But I just bought the boat, hopefully I’m good from here on out

It could have been a Merc scan tool I guess…. I really don’t know. I did run the boat another time before taking it to Johns. Maybe that time the code stored.?.? Who knows… I’m good now, that’s all that concerns me for the rest of this week. Thanks again everyone!!

After all that…and the culprit was fuel line deteriorating! Just thought I’d share something related. This spring when I pulled mine out of storage the motor would go up, but not down. Likely suspect was the relay/solenoid but still had to take it in to the local Merc repair facility. I instructed to find and fix the problem and then give it a good look over for anything else looking suspicious. Sure enough the relay was bad and fixed the problem but amongst other things they replaced the fuel line from the back of the boat to the motor. He explained that it was starting to deteriorate and if not replaced would cause problems soon. Well now I know what he was talking about. Anyway thanks for sharing your troubles with us as has been mentioned before by other members, there can be so much learned from IDO forums!

thanks Tom for posting what was wrong!!
sorry I wasnt able to help you out,but there is always next time,and we will hope there wont be,you have been through enough already!!!

glad it was figured out,and quickly,kudos to the guy who stuck with it and fixed it!!!!

I think we all learned something here. Its extremely frustrating to work on new things these days with all the electronics, but this one turned out to be non-technology related.
Kind of interesting though that others have had that same issue. I wonder if there was a bad run of those lines? I certainly think that ethanol had something to do with it from the prior owner.
The gas here in the upper Midwest is terrible at best.

CaptainMusky wrote:

I certainly think that ethanol had something to do with it from the prior owner.

A 2008 outboard would have had fuel lines that were ethanol resistant. Fuel lines degrade, they always have and always will.

This is just one more reason to keep up on maintenance.

1. If you’re not running a high-quality fuel filter and water separator unit, install one now. BTW, they are two separate things. Every fuel filter does not automatically separate water, so just having a filter is only half the equation.

Personally, I’m a fan of Racor filter/separator units. They are not the cheapest, but IMO one of the best out there.

2. Change your filters every year. Carry a spare filter as well. If possible, dissect the old filter to check for debris. If any there is any significant amount of debris in the filter, find the cause before it becomes a real issue.

3. In all marine applications, and in fact any engine that only sees periodic use, I’m a big fan of burning down the fuel supply to the minimal safe level before refueling. On my big pleasure boat, I try to take it below 1/4 tank before refilling. The idea here is to get as much of the old (and possibly contaminated) fuel used up as possible before adding new.

Twice, I’ve gotten nervous about the length of time I had fuel sitting in the tanks, so I’ve actually pumped off fuel, inspected it for contamination, and then burned it in my truck just to get rid of it.

On my tractor at my hunting property, I try to run it down to fumes. I only use the tractor for 5-6 hours a month, so if may take 6 months or more to burn a tank and that’s too long. I don’t add fresh as a “top up”, I keep burning it until the tank is just above empty.

Grouse