1991 Merc 200 EFI issue

[wiliermdb]

My brother attempted to take his boat out a couple of hours ago and it warmed up fine but it will die about 20 - 30 seconds at idle and die as soon as it's placed into gear. It did this at Thanksgiving down here in LA after we ran it for 10 miles. Had to hand crank it onto the trailer.

We cleaned a screen in the fuel system at Thanksgiving, quite dirty, and he replaced the fuel/water filter that's on the engine as well as all fuel lines from the tank to the engine.

Any ideas where to start troubleshooting? 

[Rich_V174SS]

I didn't know Merc was making EFI engines that far back, I thought they started coming out in the mid-late 90's. Sounds to me like a fuel related issue. When you say you cleaned a fuel screen in the fuel system where was the screen located? Was it inside the fuel injection pressure tank? I would also check that the high pressure pump within the tank hasn't gotten gummed up and frozen from sitting which will drastically affect the fuel pressure. See if you can get a fuel injection pressure gauge to connect to the system to check fuel pressure.

[wiliermdb]

Good idea. Yes, it does have a schrader valve on the fuel system. I remember seeing that. It's a Merc 200 XRi and the screen I cleaned out was on the upper right of the airbox cover. It was under an aluminum cover and it looks like a top hat. I'll see if I can find a photo and post it. Unfortunately I'm not with him now. He's 7 hours away and I have a fuel pressure gauge.

I'll get back to you with some more info.  Thanks

[wiliermdb]

Here's a link to a diagram of the fuel system.  The item I cleaned is #7 in the very top box of the diagram.  Compression is perfect on the motor.

http://www.marinepartsplus.com/catalog/mercury/serial/V-200XRI_EFI/817418+90/572-90

I just got a call from him and he said there's a small filter (see thru) on the motor about the size of a wine cork and he stated while the motor was on idle it was not full. Maybe 1/3 full at the most. May be a pump issue, low pressure.

Will let you know what he finds out.

[wiliermdb]

Merc fixed.   Spoke with my brother today and he's on cloud 9 now that the motor is running perfect. While here we cleaned out a filter screen that was pretty junked up. Back in Austin he launched last weekend and it would not idle and kill as soon as it was put in gear.

He removed and replaced the fuel/water separate and a couple of the fuel hoses.Some of them were clogged with some gray colored gunk.  Started right up and then after backing off the trailer it would kill. He removed the engine cowling and adjusted the idle position screw to bring up the RPM's about 2 - 300. That did the job and he ran the boat for about 30 miles on Lake Austin today.

After the ride it had no more issues.   

[MarkS]

That's great news, glad he got it sorted out!  Looking at some of the prices on the fuel system components on that motor scared me!     I'm not even sure how long the newer "alcohol resistant" hose and stuff is going to last, but if you're running older fuel lines, filters, etc. it's just a matter of time before problems start to rear their ugly head.  Even without the ethanol, I guess a guy ought to replace that stuff every so often.

[Rich_V174SS]

I'm glad it's running but I would still check a few things on the engine. For one, on a fuel injected engine turning up the idle screw changes the setting for the throttle position sensor. These are usually set using a volt meter and a service manual as idle is electronically controlled, not mechanically. I would check to make sure that the engine is running on all cylinders, meaning you have both spark and fuel on all 6. Check compression too. For an electronically controlled engine to suddenly need a change of settings to run sends up a red flag. I've seen many Mercs drop a cylinder or two making them difficult to run and hold an idle. Sometimes it would be as simple as needing a new ignition coil, other times needing a new piston.