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I went for one of the last outings yesterday with my 2008 Whaler and Mercury 60HP bigfoot.
All season long I quite often had problems running at 1400 to 2000 rpm anywhere in between (a swing of 400 to 600 RPM). When I tried she would constantly (every 1-2 sec) fluctuate between these two RPM's. I could run smooth anywhere above that upto WOT (6000 rpm). As the engine always started and normally I don't plow thru the water at those RPM's I thought I wait until this winter to find out what is wrong.
Now yesterday 50 deg.F she started fine as always but was running what sounded like at 3 cylinders at idle (800-900 rpm) I had to goose her a little and bring it back to idle to get her to purr on 4.
After about an hour of running at 1000 to 1200 rpm she would stall, I did notice when I changed trim either by me moving aft or using engine trim she would stall. Started up easily every time and if I would try to run slow/idle she would stall. I did not get any alarm soundings and of course I'm using clean new gasoline.
Hence based on trim change causing stall I would expect this to be a fuel problem. But this isn't a carburated engine with a float so how could it. Has anybody else run into this problem?
At the end of last season I had a full service done and under warranty received 3 new coils (as 1 was replaced previously). The engine has brand new plugs too. (< 25 hrs)
Could this be injectors? fuel pump? or what?
As mentioned she runs fine between 2,500 and all the way to 6,000 RPM with standard expected fuel economy. It was that pesky 1,400 to 2,000 RPM and now no good idle.
Help

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How many hours on the motor? How many hours do you run a season?

If you do a lot of running at low speeds, (1-2k) you may have carbon buildup. It is commonly recommended that all owners occasionally run the boat wide open for short periods (10 minutes). In the old days it was referred to as "burning off the carbon". I would do it at least once a week or once every 3 outings if conditions allowed.

The term "Full Service" at a dealer is not very clear as the definitions vary.

When were the fuel filters (low and high speed) last changed?
When was the vapor separator tank (VST) last cleaned?

Do you treat your fuel?
Do you treat your fuel for winter storage?

I would add some Mercury branded fuel treatment and try to clean out the fuel system first.

I would do some hard high speed running 2nd.

I would consider sending out your injectors for professional testing and cleaning ($50/each).

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X 2 on what Phil said. Even at 25 hours, I would check the plugs for carbon buildup.

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You should do a de-carb but I think your problem is in the fuel supply.

Loose or worn connection, bad hose, bad primer, clogged filter, etc.

You say they did a full service, did that include your filters? Did you have this problem ever since the service?

You might want to check everything for tightness.

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I have a hard time believing a fuel-injected four stroke has problems with carbon buildup. Still, it's easy enough to check the plugs. Likewise, it is hard to believe that a fuel system that is perfectly fine delivering large amounts of fuel at WOT would have trouble delivering smaller amounts at idle and low speeds. To me that rules out fuel pump, filters, fuel injectors, etc.

Your experiments with trim where the motor would stall by either changing the motor's trim, or simply moving around in the boat, are interesting. I don't know quite what to make of it. What was the deal with the coil recall? Is there a description of what the symptoms were that caused the recall?

Tim

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Guys thanks for chiming in I should have been more specific. 2 seasons ago.
The engine would not run all the time (just intermittent), at time of the service, after they went thru every thing (to figure out why sometimes it ran fine and other times it wouldn't even start) electronic and fuel. Service history showed that the previous owner had 1 coil replaced under warranty. It was determined that my other coils needed to be replaced which was done under warranty. I still had to pay for new filters, plugs, etc. She ran and started fine after that although sometimes I had the surging but could stop that by turning of the engine and restarting the OB. It was sometimes a nuisance but bearable and I was going to get that looked at during the winter when the dealer would be a little slower although they never are with snow mobiles already in the shop.
Following in answer to Phil's questions;

370-400 hrs on engine and I now run approx. 100 hrs a season, 60 hrs @ 900-1200 rpm, 15 hrs @ 3200-4200 rpm, and 15+ hrs @ 5200 to 5800 rpm.

Yes I do put around a lot with the Admiral but I never go without going WOT. i.e the boat always gets a burn out. EMC(computer), injector type engines very seldom get carbon built up and I do not have any as I checked the spark plugs, which looked clean. When the Admiral isn't with me I sometimes run an hour or longer above 5000 RPM. This engine always gets a work out.

The low fuel filter I changed in May of this year. I don't know about the high????

Don't know if the VST was cleaned (where located and how?)

Yes I do treat my fuel (in all my seasonal engines for the last 40 years) with a storage type like Sta-Bil and currently (last tanks of the season) use Sea Foam in my gasoline. As I have removable tanks I'll empty them for winter storage. I'll try some Mercury brand fuel treatment before I put her away or take her to the Merc. dealer.

I'll check everything for tightness too.

As mentioned B-4 I do run her hard at least once every time I'm on the water. I really think it is a fuel problem and the filter is clean so this VST intrigues me.

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EJO,
I am sure you probably know more about your motor than I do, but I had a buddy with a larger Mercury on his Dauntless that exihibited the same symptoms. He took it to a non mercury certified marina outboard tech who checked the fuel pump, rebuilt carbs, and replaced filters and thought he had the problem fixed but it reappeared shortly after my friend received his boat back and did a on water test. The 2nd time he brought it to a mercury tech who ran the motor and stated it was a secondary fuel pump that the motor had was having intermittant problems. I dont know if your motor is the same and has 2 fuel pumps or maybe it only has one and it is exihibiting the same intermitent problems but it might be good to check that out.

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Thank you jgortva but this is a injector type motor as previously mentioned it is a 2008 4 stroke non carburated engine.
I don't know if I have one or two fuel pumps.


For all other readers I did forget to mention that I never pump my ball in the fuel line and if I do it never gets firm/hard like it does on my 2-stroke motors.

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So one mechanic had no clue but changed a coil, so the second clueless mechanic figured he would do one better and replace all three. Luckily they also serviced your engine and got you back on the water.

I think you have a bad primer/fuel line. Is there any way you can borrow a known good tank/fuel line to do a test?

That doesn't mean that is all that's wrong. I would do a visual inspection with particular attention to anything the dealer touched. Make sure everything is tight and in the proper place. I had an engine where the dealer replaced the spark box and shifted the kill wire just enough that it would rub the flywheel, sometimes. This had no effect for some time because it would only rub at certain times and then as the insulation got worn it became more of a problem.

The next thing I would do is pull the fuel filter and read what has been happening over the summer, pull & read the sparkplugs too. Maybe nothing special, but that is useful info.

I would also check the battery health & connections because this needs to be done & you are right there. There is also like a 0.05% chance you have some freaky bad ground that only shows when the boat vibrates just right or you tilt the engine.

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Fuel injected motors have two fuel pumps. One is called a lift pump, that draws fuel to the motor. The second is a high pressure pump that boosts the fuel pressure in the fuel rail so it sprays out of the injectors. The high pressure pump is inside the VST.

While I don't like links to other sites, here is a tech explaining the VST for a 2010 Mercury 60 with the parts diagram.
http://www.justanswer.com/boat/6hcxz-...#re.v/287/

My understanding of the 4 stroke fuel system comes from having successfully troubleshooted a serious lack of performance on a low hour F115. The prior owner ran it at low speeds and used bad gas with no filters or treatments.

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Phil thank you for the link. You could have emailed me but thanks I will definitely try that.

MG56, yes and no to your comment about the mechanics. The first replacement was done long B-4 I owned the boat so i couldn't tell you what that was in response too. All I know is that Mercury told the Mercury mechanic after sending data back and forth to replace the coils. This was diagnosed in Wisconsin because the local Merc. Mechanic couldn't figure it out.
As for electric connections (new battery, new clamps, she has good ground) all new in May of this year to make sure I was ready for the season Again the boat runs fine for 40-70 miles in one day, which I do once a month or so, I like to go distances with my little boat and often on Lake Michigan. other times it is leisurely cruising for 3 to 4 hours on some local lake or pulling the 2 person tube.
No gasoline is ever smelled by the worlds best nose (my wife) and this is an inside stored boat with what looks good supple hoses without degeneration and my clamps are either constant tension or ABA screw clamps. I speak from experience using these ABA clamps after working on many old European cars and replacing OEM hoses causing the OEM constant tension clamp not to work due to hose thickness difference.
Basically what I'm trying to tell you all connections, fuel or electric are in tip-top shape.

I'll try the VST tank clean and take her out one more time if it stops raining this weekend and will report back.

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Did open the VST and all was super clean as expected. Made service appointment next week to have a professional look at it. (he keeps the VanDam brothers boats running in tip top shape, hey it is their store)

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EJO, couple things to think about before you bring it in to the pros. Let's make sure you look at everything you can.



But this problem began this year and got worse. I've been jammed up because a new battery connection went south, it happens. It isn't likely your problem lies here but it is possible. With EFI what is also possible is your battery is not charged enough if you do a lot of short runs. You diagnose this problem by answering the following question. Do you have this problem after you run the boat 40-70 miles a day? If the problem persists after runs like this we should move on to something more likely.

I keep going back to a fuel supply problem because of the way you described the surging at a specific RPM range, and I haven't seen how you trouble shot that. You did say you can't pump the primer bulb firm, which is not something you want to see. If you have a Whaler/Merc rigged boat of that vintage you could have gray fuel line with red writing, which is something else you don't want to see.

You wrote above that you have tanks, plural, so have you ever tested that this problem could go away by swapping tanks? Which doesn't actually prove anything because I don't know what you have for tanks and it could be a miracle you haven't had a problem with them thus far.

I would like to see you do a test eliminating all of the potential external fuel supply problems before you bring the boat to the pros. With EFI you should be able to run a line right off the engine to a tank of gas. The boat could run like a champ, and narrow your focus.

Around here trips on the water are disappearing so I would charge the battery fully and run the boat on a new fuel supply. If the boat runs right I won't know what fixed it but I know I don't have to bring it to the dealer.

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It is going to the pro tonight.

No it has been ongoing just got worse this year
It's not the battery, as it is new and always has a good charge and my alternator puts out a good charging voltage of 14.1 or so (I don't look at it that often anymore because she starts good always)
Yes the problem is there from cold to hot after running all day (hours at 4 to 6,000 rpm)

that is correct I'm trying to trouble shoot/diagnose this problem
yes this is a non modified 50th edition Boston-Whaler with therefore a Mercury 60HP Bigfoot, I don't understand your comment about the grey fuel line. Do I or don't I want to see a grey fuel line? My fuel line from my two 6 gallon external tanks is black (under the sole) and grey from primer bulb to engine

these little Montauks come with 2 plastic 6 gallon tanks under the RPS. I go thru enough gasoline(Michigan Marine (Valvetec) non-ethanol) that I constantly change between the 2 of them without any difference in operation. It is not the tanks

she does run like a champ except at between 1400 & 2000 rpm. No I have not run a hose into a tank direct but did measure the outlet pressure of the high pressure fuel pump which was 37-38 psi yesterday.

Yes it was cold yesterday while testing the boat after opening and cleaning(not needed) the VST. Again good idle, good top end WOT, but again(still)surging at the 1400 to 2000 rpm. Ran her hard enough to get her up to operating temp and no changes

She's going to the pro tonight against my will.

Thank you everybody I'll let you know.

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We probably could have saved a lot of time by me either seeing the boat or talking to you on the phone. You know what you are doing and you have checked just about everything you can, but this is the problem with trying to communicate like this. Most of the questions I ask aren't necessary and just add to the confusion.

One small point, I still don't see how you have eliminated the fuel supply as a problem, more specifically the fuel line/primer bulb assembly. This is a very common problem and it can present exactly like what you are seeing.

You can't prime the bulb hard. Why not? Is it old, not oriented right? Neither of these is a good thing.

You say it is one part black hose and one part gray, and it is like 8 years old? I'm still looking to eliminate the fuel supply line as a problem but this doesn't help.

Mercury uses gray line, and the older fuel line has red writing on it. The fuel line with red writing on it is bad, and should be replaced with the newer gray line with blue writing, or an equal product. Did your original fuel line in front of the primer get replaced, and are there bits of the old failed line in the primer? Even if that isn't the problem the gray line after the primer could have a lining failure which is fine either at idle or full throttle, and is flakey at a moderate flow rate.

Passing a random fuel pressure test does not eliminate the fuel line assembly as a problem. Reading the fuel pressure while you are having a problem will.

All you have to do to rule out any external fuel supply problem is to run the boat on a known good fuel line/tank. A lot of mechanics don't even work on your boat with your fuel supply. There is a reason for that, it is just too common to have a problem on the boat side of the engine.

I'm sure I have spent more energy on this one potential problem than what it is worth, but it just has not been eliminated. It might be worth telling your mechanic that.

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MG I got her back last evening and as we had fantastic weather here in SW Michigan (74 F) I immediately took her for a spin to make sure it was fixed like they said.
It was the boat runs tops.
Here is what they said caused the problem. The THERMOSTAT was stuck slightly open screwing the EMC in thinking the engine was running cold and needed more fuel (rich) which was exaggerated at the RPMs mentioned and not at wide open.
So they replaced the T-stat and also the the final grey Merc line which had Red writing on it. The previous owner already had replaced the line from the tanks to the bulb but not the line from bulb to engine. He also must have used automotive gasoline as the line was completely deteriorated. (I was lucky that no debris got as far as my fuel filter(s) but still it was bad. I should not have assumed that the previous owner would always have used non ethanol (marine) or at least treated gasoline.
Last but not least they replaced all 4 spark plugs.
She runs great now had mirror water and with some trimming got her up to 6K rpm and her upto 36 mph.
I now can winterize (change oil, fog, lube, etc) the engine and put her away for the heavy winter here in Michigan and know I can go boating next April without any worries.
Again thank you everybody for your inputs.

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Glad the problem is solved, priceless.

But, the computer gets it's temp reading from a sensor, not how much the thermostat opens. Shrug...

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Yes we know the thermostat is not connected to the engine management control and;
Yes but if the T-stat stays open all the time the engine can't get up to temp and therefore the temp sensor tells the computer it is cold get some more fuel into the mixture. It was running real bad in those lower RPMs when the water temp was 50F. Now it doesn't as the T-stat stays closed when needed, giving the sensor a warmer reading which in turn sends a signal to the EMC telling it what to set the mixture at.

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E-J, thanks for the followup - that was pretty subtle! Kudos to the mechanic for finding it too.

It's great when people post the resolution to their problem - helps out the next guy!

Tim

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Tim thank you and yes pretty subtle that cold temp was the problem.
I picked this Mercury dealer as it is owned by the VanDam's. Kevin and Jonathan both elite pro tournament anglers and Bassmaster champions run around there quite often. I even had a courtesy conversation with Kevin when I dropped my boat off. He said he was going fishing as it was 70 deg. and had a mechanic pull his boat around.
I got lucky that the mechanic that keeps Kevin's boats in tip top working order was the one that worked on my little engine. He keeps that Nitro Z21 with the Mercury Optimax Pro XS2 running flawlessly for Kevin which is important when you make millions just fishing. lol

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So you may use more fuel but with a fuel injected engine you aren't going to have surging, well not because of a thermostat. So while the thermostat may need to have been replaced that wasn't the problem, nor were the spark plugs they replaced.

These are the pictures you uploaded to the other site of the fuel line they replaced, (gray Merc fuel line w/ red writing) >>>

[IMG]http://img.photobucket.com/albums/v130/Qtrmeg/RedMercFuelLine0.jpg[/IMG]

[IMG]http://img.photobucket.com/albums/v130/Qtrmeg/RedMercFuelLine1.jpg[/IMG]

Now that, I would say, has been causing your problem for a long time. I would also suggest that you replace the entire fuel line assembly and keep the old one as a spare.

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MG56 thanks for posting the pictures. Yes my line from bulb to engine intake was bad as evident by the pictures. None of the deterioration reach any of my filters and or the VST as those were checked and re-checked.
So I don't think that caused the surging for two seasons and stalling when the water was cold.

My boat has black A1-15 fuel line from tank(s) to bulb and now new Mercury Grey (Blue lettering) from bulb to engine.