Mariner 60hp 4 stroke EFI 2003

After about 20 minutes of running, engine starts to die. I can keep it running normally by pumping bulb almost constantly. Have tried different fuel tanks, new fuel line and renewed both fuel filters. Replaced mechanical fuel pump twice, thinking maybe first fuel pump was faulty, have also ran fuel line straight to fuel pump to rule out sucking air but problem is still there. Wondering if anyone has had same problem or has any idea what is causing this please.

I've been waiting a long time for this. I had the same thing happen to me once. I changed EVERYTHING! It turned out to be a KINKED BREATHER HOSE from the valve cover to the airbox. I finally figured it out when we were running at speed with me pumping the bulb and the dip stick blew out like a bottle rocket. We took it back and found that the hose was kinked and the large bead inside was turned sideways restricting it even more. With no way for the crank case to vent the pressure built up and pushed against the diaphram in the fuel pump harder and harder until it couldn't move. Pull that hose off the engine and blow through it. Put it back carefully so it is not smashed, kinked, clogged or whatever and let 'er rip. I would have never guessed. It was a fuel problem all the way. $600 and an entirely new fuel system later it was still a fuel problem, that's impossible. I hope that fixes it. You and me will be the only ones this has ever happened to. Just remember, we live in the future now everything is complicated and not what it seems. Good luck!

Thank you Dockside Marine Repair http://www.marineengine.com/boat-forum/member.php?51454-Dockside-Marine-Repairfor reply, was yours same engine? I am now on my third mechanic trying to fix this problem, first one spent a month on it and got fed up with it. Second one couldn't find what was wrong either then he moved jobs. Third one is looking at it today.On my engine there are two hoses coming from valve cover, in the service manual one is labelled as "Crankcase Breather Hose" and the other is "Crankcase Vent Hose"

The engine I was working on was a '05 Suzuki DF-50. I know it's different but the system is fundamentally the same. The fuel feed pump runs off the cam and if the crank case pressure is too high it can leak past the O-ring on the fuel pump base and restrict the diaphram movement. The crank case breather hose is the one that gave me trouble but check them both. Remove the oil fill cap and blow into it from the airbox end into the valve cover. It should be easy and free flowing. In school they also warned that the silicone on the upper valve cover baffle (internal) can and has caused such problems. Fact is you can run all day if you keep pumping the bulb. Not the tank, not the pump, and not anything in between. Those parts have already been replaced to no effect. You might be wasting your time going any further down the line, I did, and it gets expensive after the fuel feed pump. I ran this thing with vacuum and pressure guages hanging off of it and went around and around for a month literally replacing or bypassing everything from the fuel tank to the contents of the VST. Damn breather hose. it makes sense now. The primer bulb can make about 20 psi tops. Not enough for the engine to run at speed, not even for 100 feet. The high pressure fuel pump is fine if you can go 1/4 mile. That's how far this one would go, and run perfect. All of a sudden it would quickly idle down and die. There is a possibility of a partially stuck float or needle valve in the VST that could act the same way but the breather hose is real easy to check. A fuel pressure guage on the outgoing side of the fuel feed pump should read at least about 7 psi all day. Yours will start to fall off immediately after take off and within seconds hit 0. I'll bet you a one eyed watch dog.

Hi Guys
I have a similar problem with a mariner 60EFI 2005

Mine always starts on the button when cold and will run for the first hour and then maybe when i am cruising it will stall and will not start again I can pump and get pressure and it still will not start .
when it is running if I keep pumping it will normally stay running.
when I try to start it will sometimes start as if it running on 3 cylinders,hunting and backfiring
If I lift off the hood and open thethe cap on the high pressure fuel tank before the injectors and release the pressure by bleeding this tank it starts right away.
I have had it in the shop twice to no avail and changed fuel lines and fuel pump and nothing has fixed it except bleeding the high pressure side and it will run for another hour and maybe longer before i have to do it again.
I have had to get a new bendix on the starter as well from trying to start it before i found this cure.
any answers
Ron

I think you have a different problem JFK. Fortunately your ingenuity has apparently narrowed it down to the VST (vapor seperator tank). You shouldn't have to bleed off pressure for the engine to run properly, being as that helps it you have a malfunction in the VST assembly. It appears the VST is somehow building up internal pressure. The Mercury counterpart has a vent line with a small filter-like check valve wich would alloy the tank to vent properly and regulate pressure. If your engine has such a hose you could check it first. On the other hand the problem could be inside the tank. I'm picturing a leak at the grommet where the high pressure fuel pump plugs into the top of the VST to send fuel to the injector rail. If so this leaking fuel could be raising the pressure in the VST and even possibly foaming up or aggitating in some way. There is also a pressure regulator valve in the bottom of the VST wich regulates the fuel pressure in the injector rail by letting excess pressure return to the VST from the injector rail. The o-ring at the bottom of the pressure regulator could be leaking or the regulator itself could be faulty. A series of fuel pressure tests at different points in the system should be able to narrow the problem down further. Thing is, there should not be any considerable fuel pressure inside the tank itself. There could be 5 to 7 psi of fuel pressure coming from the fuel feed pump into the tank but when fuel enters the VST it is regulated by a float and needle valve like a carburator. The electric pump inside then produces sufficient fuel pressure to the outgoing injector supply hose. The fact that the engine can run well for an hour suggests that the fuel system is producing good pressure and does not have a restriction, but an internal leak maybe. A strange solution to a strange problem.

Hold the phone, I may have steered you wrong mate. The cap you speak of, does it look like the air valve on a tire? If so then your system is different from what i explained. The Mercury engines here in the states quit using that system early on, around 2000 I think. We haven't seen Mariners for many years. The early system with the cap like a tire had the pressure regulator outside the tank in top. It looks something like a thermostat of sorts. Now that that is clear I ask; When you release this pressure is it coming out or sucking in? It also makes sense that it could actually be sucking air into the tank as it could be running out of fuel causing a vaccum. If that is the case then the needle valve in the tank is likely stuck, it happens. It could be partially stuck and restricting the fuel flow into the VST wich should be nearly full all the time. You culd try removing the drain screw at the bottom of the VST and letting the fuel drain out completely then pump up the bulb of remove the incoming fuel hose and blow into it to see if there is a restriction. A restriction can be a tricky problem. It could be anywhere from the fuel tank to the VST and cuase problems anywhere else. Check again and make sure you're venting pressure and not the other way around. I think it's sucking air into the tank when you vent it.

Update on my problem. Although i have only managed to use engine twice so far but fingers crossed all seems ok.
It seems like I may have had three faulty fuel pumps.
First mechanic who looked at engine diagnosed faulty fuel pump so fitted new one. Took it for a run, same fault returned after about an hour, back to mechanic who said new fuel pump was faulty, so returned pump for another, this was fitted and still the same fault, back to mechanic again, who went all over the engine thinking maybe there was some other fault, by now he had spent quite a bit of time on my engine. He wanted to open up fuel pump but was reluctant as it would void the guarantee. He was now having problems getting another fuel pump as he was trying to get a third one under guarantee and (as he was not an authorised Mercury/mariner mechanic) they were now doubting his diagnoses and were not being very helpful.
In the end I took the engine to a Mercury/Mariner dealer who said it was a fuel pump problem and got the go ahead to strip pump where they found plunger shaft was sticking. Had to wait for new fuel pump as the main distributors were out of stock!
As well as new pump the fuel filter was removed and changed for a different kind as they thought this was also causing problems.

Hi ? Dockside Marine repair
Yes it is the one with the Tyre type valve at the top of the VST tank and when it is vented it releases pressure because it sprays out fuel and not sucking in air.
This is a 4 cylinder Mariner EFI and I dont know if it is available in the US as i dont see any write up on this this particular engine in any of the Us forums
I am located in Dublin Ireland
I got myself an in line fuel pressure gauge and tested the low and high pressures either side of the fuel pump and this is all Ok.
As far as I can Judge it is not sucking.
Thanks
Ron

New to forum attempting to post message on issue with my Mariner 60hp 2 stroke, Have a 1996 Mariner 60 HP fuel injection with RPM gauge not working. From viewing online searches the rectifier could be the problem. Where is the rectifier located on this motor so that tests can be performed to determine if operating? any help would be appreciated. Sorry jumping in on your issue but would like to get the question answer if you can help.

The regulator/rectifier charges the battery by converting AC voltage from the stator into DC voltage for the battery. The byproduct of this conversion is the tach signal. Often times when a regulator/rectifier is faulty the tach not working will be the first clue. Now you need to see if the battery is changing, easy if you have a volt gauge, if not you need a voltage meter. Check your battery voltage with the engine off, let's say it reads 12.3V. Now start the engine and check again, it should read 13+ and rise with RPM to full power around 3000RPM. If the battery isn't charging and the tach doesn't work there's a really good chance the regulator/rectifier has failed. Take a look at it, it's a metal square about the size of a pack of non-filter cigarettes. It should have 2 yellow wires, a red wire, and a grey wire. Some of them are black and some are filled with an amber colored resin making the circuit board inside visible. You're looking for a brown or black spot inside the resin on the circuit board that would indicate something got hot and burned. If that's the case then it's bad, go ahead and replace it, it's a simple and straightforward repair that you can do yourself. Disconnect the batter before you start. The part typically costs about $125. The other possibility is that the charge coils on the stator have failed, but less likely as the regulator/rectifier is a much more common failure, cheaper part and easier replacement. Hope this helps.

Dockside Marine Repair said:

The regulator/rectifier charges the battery by converting AC voltage from the stator into DC voltage for the battery. The byproduct of this conversion is the tach signal. Often times when a regulator/rectifier is faulty the tach not working will be the first clue. Now you need to see if the battery is changing, easy if you have a volt gauge, if not you need a voltage meter. Check your battery voltage with the engine off, let's say it reads 12.3V. Now start the engine and check again, it should read 13+ and rise with RPM to full power around 3000RPM. If the battery isn't charging and the tach doesn't work there's a really good chance the regulator/rectifier has failed. Take a look at it, it's a metal square about the size of a pack of non-filter cigarettes. It should have 2 yellow wires, a red wire, and a grey wire. Some of them are black and some are filled with an amber colored resin making the circuit board inside visible. You're looking for a brown or black spot inside the resin on the circuit board that would indicate something got hot and burned. If that's the case then it's bad, go ahead and replace it, it's a simple and straightforward repair that you can do yourself. Disconnect the batter before you start. The part typically costs about $125. The other possibility is that the charge coils on the stator have failed, but less likely as the regulator/rectifier is a much more common failure, cheaper part and easier replacement. Hope this helps.

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thanks very much will try this procedure, also to access the regulator/rectifier, it appears to be located behind plastic cover on the right side of the engine, engine model 7060412DD