Mercury Mariner 225HP 3.0 V6 EFI 2-st...

Author Message   Ondrej Travnicek New member Username: ondrejt Post Number: 1 Registered: 04-2008 Posted on Friday, April 18, 2008 - 08:01 am:    Before putting my boat on the water I had the Mercury specialist mechanics "check" the engine as I was convinced the idle was rough and uneven and too high - approx. 900rpm compared to recommended 650rpm. They ran the engine on idle, water supply was connected, water was running through the engine, they tried to increase the revs a bit and deemed the engine being OK. Next day I put the boat on the water, went to buy 100lts of fuel (there were many other boats buying the fuel from the same bowser and suffered no problems). I was sure the sound of the engine was more "rumbling" then any time before and the whole hull seemed to be shaking. When I took the boat out of marina and was running up to approx. 2500rpm it was working. When I tried to take it up on the plane and put in on the full throttle, it shut down/stalled. I switched the engine off, gave it 5 seconds and tried to start it with no success. Another 5 seconds later the engine started and worked fine until I gave it full throttle when it stalled again. When running around 2000-2500 revs it works and after I cleaned the sparkplugs, re-connected loose connector to one of the spark plugs and cleaned the fuel filter the idle is now smooth. Mates whom I talked about the problem seem to be equally divided in two groups: One think the fuel pump or injectors are full of dirt from the fuel tank which was almost empty for over 3 months but while I consider mysefl quite handy with cars and engines I have no idea where the fuel pump is or how to take out the injectors from an outboard to clean them The other group thinks there must be something wrong with the cooling and when put into high revs (up to 4000rpm) the engine starts heating up and the ECU shuts it down to prevent any damage. As I am out of ideas I hope you might be able to help.   Graham Lamb Senior Member Username: galamb Post Number: 2999 Registered: 05-2007 Posted on Friday, April 18, 2008 - 07:17 pm:    Well, if you are taking a poll my vote would go with a fuel problem - definately sounds like a clog - which could be at the tank pickup, somewhere in the line, bad anti-siphon valve, air leak in the fuel line, bad fuel pump (either primary or electric), crud or water in the vapor separator, clogged fuel filter, clog in the fuel rail, bad fuel rail pressure regulator, clogged injector, bad electrical connection to one or more injectors or a number of other things that don't immediately come to mind... Sorry if I got a little convoluted there, but my point is, you have a very complex engine there which leaves you two choices - 1) get a service manual and start troubleshooting or 2) take her in and get someone to start troubleshooting. You don't have an outboard that you go over to with a screwdriver and tweak a carb needle valve to smooth her out...   Tony Delio Senior Member Username: tonyob Post Number: 1434 Registered: 05-2001 Posted on Saturday, April 19, 2008 - 03:21 pm:    Ondreij, Graham is correct; these engines are complex, but it could be a simple problem anyway. If the engine cuts out abruptly when you push it past 2500 RPMS, it could be the stator. If it does start to rev higher,but then starts to back off and stall gradually, it is probably fuel related. If my memory is correct, an overheating problem would cause it to go into slow mode, which would prevent it from reving past 2500 RPMS, but would not cause it to shut down. You have two fuel pumps. A primary pump which works on crankcase pressure, and a high pressure pump which is electric. The primary pump sends fuel through the fuel filter and into the vapor separator. The electric pump draws the fuel from the separator and pumps it through a screen and into the rail. The fuel returns to the separator where a check valve regulates pressure. I always start by testing the pressure at the fitting near the electric pump. If the pump is not drawing fuel the pressure will drop to zero. If this is the case, the primary pump might be bad, the vapor separator may not be functioning properly due to a clogged hose or a stuck float, there is a leak in the rail or the return, or the check valve may not be holding pressure. I may be wrong, but I don't think the fuel injectors are the problem. Tony   Ondrej Travnicek New member Username: ondrejt Post Number: 2 Registered: 04-2008 Posted on Sunday, April 20, 2008 - 04:48 am:    Hi guys, Thanx for your advice. Yesterday I´ve cleaned both fuel filters,dissembled the "container" in which is the fine wire mesh filter and the floater thing (I´m not sure whether that was the separator as English is not my mother tongue).I´ve changed spark plugs as well and ran the engine at idle which finally sounded like it used to. I´ve put the boat on the sea and when moored put it in the gear and gave it full throttle for approx. 5-10 seconds and it worked fine. Then we took it out of the marina and it worked fine even went up to over 4000rpm. We spent approx. 15minutes cruising at 3200rpm and then went further towards one of the near inlets. After about another 10minutes at 3000rpm the engine shut off again and agter I started it and on top of the normal engine sound it was again making that low rumbling tone (like if you make farting noises with your mouth) and the whole boat was shaking strongly. It seemed to me like the engine worked on only a few of the cylinders but due to the rain, strong wind and waves I couldn´t check on anything. We made it back to marina and hopefully one of the guys on the island will have a look at it in a week or two time. To get the boat to the service center would mean I´d have to organize a barge to put the boat and trailer on, have it shipped to the mainland, get the mechanics to come to the harbour, tow it to their workshop and after they repair the engine it wwould all have to be done again in reverse order. It might end up like this but it would mean several hundreds of dollars on top of whatever they´d charge for the repair, therefore I´m trying to find out advice which might help me to find the problem and repair it myself.   Tony Delio Senior Member Username: tonyob Post Number: 1435 Registered: 05-2001 Posted on Sunday, April 20, 2008 - 11:31 am:    Ondrej, Since the engine ran well for about 30 minutes, I would say that you are close to a solution. Something that you did made a big difference before the same problem returned. The float that you mentioned is in the vapor separator. This chamber fills with fuel, and causes the float to close the valve at the top of the chamber. When vapor accumulates at the top of this chamber, it prevents fuel from entering, and this eventually causes the float to drop and opens the valve. When this happens the vapor is drawn into the intake manifold and burned with the fuel mixture, and fuel can enter which causes the float to close the valve. If the vapor can not be drawn off, eventually there is no fuel for the electric pump to use. My guess is that there is an obstruction which is preventing the vapor from being drawn into the intake manifold. Tony   Ondrej Travnicek New member Username: ondrejt Post Number: 3 Registered: 04-2008 Posted on Sunday, April 20, 2008 - 05:44 pm:    thanks Tony, I´ll try to have a look at it over the weekend and will let you know if I was succesful   Ondrej Travnicek Member Username: ondrejt Post Number: 4 Registered: 04-2008 Posted on Saturday, April 26, 2008 - 01:22 am:    hi Tony, I went to check the engine again and found out that I might have forgotten to connect one of the very thin rubber hoses to the small tube-like breather coming out of the electric connector on the top of the vapour separator. I am not 100% sure whether it was originally connected or not. When I started the engine today it was running smoothly and the small hose did suck the air in. As the engine sounded fine I took it on the water and it was running OK for approx. 15 minutes and was willing to go up to approx. 5000 revs. I was running it on 3000 revs and then it started suddenly loose power but when I added a bit of throttle it worked fine again. Then after those 15 minutes it stopped eventough it seemed to start loosing power and after approx. 5 seconds the engine stopped. It started right away and worked fine up to 4000 revs and again choked... this repeated 4 times and after that the engine started to have uneven idle and seemed to lose power again so we limped back to marina. Besides that the alternator driving belt snapped again, this time it lasted only 6hrs of engine time. It seemes there is something wrong - probably the alternator "wheel" and the "wheel" on the engine are not aligned properly as the belt seems to be shaving off black dust. The local Mercury mechanic thinks there is either some bad connection - a wire is broken or the earthing of the cables coming from ECUs is loose, or there is something wrong with one (maybe even both) of the ECUs. These cost 1500 AUD each which is a big hit to my budget. The dealer here is obviously a thief as he charges AUD 80.00 for the alternator belt while on one of the US marine parts website it cost only USD 15.00. Unfortunately they do not ship parts internationally... Anyway, I am again out of my humble wits and wonder if anyone has any ideas...   'Bandit Advanced Member Username: timebandit Post Number: 283 Registered: 09-2007 Posted on Saturday, April 26, 2008 - 07:28 am:    That may the computer map sensor with the small hose. That needs to be working for the ECM to fuel the motor correctly. That may be part of your problem. Lack of juice from a busted alt. does not help either.   Ondrej Travnicek Member Username: ondrejt Post Number: 5 Registered: 04-2008 Posted on Friday, May 16, 2008 - 08:14 pm:    So far I´ve changed everything from fuel lines, water separator (both were full of some brown gunk), membranes and springs in a fuel pump, gasket in vapour separator and spark plugs to no avail. Now everyone seems to think the problem is in the electric high pressure fuel pump so that one will be changed in next 2 weeks and if that doesn´t help then the boat will need to go to the mainland. When the outboard mechanic comes to change the pump I´ll ask him to look at the small hose and map sensor as Bandit recommended. Fingers crossed...

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