2003 22V Mercruiser 350 Mag MPI dying at the Dock

[Powday]

Took my 22v out to test ballast install and ran into problems keeping it running at the dock. Engine cranks right away and runs for 1-2 minutes before slowly chugging to a halt. I turn the key off, and it immediately cranks again and runs for another 1-2 minutes. On some of the tries I'm able to rev and hold it at 2k in neutral, but it eventually dies out again in the same timeframe. Engine Serial # is OM391305. Would like to rule out anything simple if possible, but my hunch is that it's a fuel pump issue.

Some things I noticed:

1. When turning the ignition 1 click to the right I hear the normal alarms, but (what I think is) the boost pump sounds a little funny - almost like a bad bearing squealing noise at varying pitch and it runs longer than I think it should even shortly after ignition likes it's trying to keep up.

Info:

1. Plugs, plug wires, and rotor were replaced last year and it doesn't run rough so I don't think that I have an ignition problem.
2. Fuel/water filter was replaced last year, but I'll probably replace anyway.

Questions:

1. Do I need to cut the fuel off somewhere to change the fuel/water separator?

2. I think this engine has a low pressure boost fuel pump, and pump and fuel cooler (high pressure?) pump. Where are these located?

https://www.perfprotech.com/mercury-...60?umodel=4922

https://www.perfprotech.com/mercury-...50?umodel=4922

3. How do you test fuel pressure at either of these or tell if it's a pump problem?

[freeheel4life]

Schrader valve at the fuel rail to test fuel pressure.

I like to go to Mercs webpage and launch their parts catalog. It suck on a phone but on a laptop or desktop it's great. Pop in your serial and it will get you your motor as built. Then you can use that info to cross shop elsewhere on the web and make sure you are getting the right parts.

Possible that high pressure pump or even FPR could be the problem. From my experience if it's the low pressure pump you will only stumble at high RPMs and heavy loads, but YMMV.

[Powday]

Thanks and great suggestion. I got on Mercury's site and looked at the parts catalog, and spent a little time on the boat this afternoon finding where everything is.

I have a inline fuel filter, fuel/water filter, low pressure pump, and simple fuel pressure gauge on order. Google helped me find another great post on this site for the high pressure pump, regulator, and everything about the Cool Fuel box under the starboard side.

http://www.tigeowners.com/forum/show...ement-2000-21v

Will start troubleshooting later this week and see where it goes.

[Powday]

Hopefully back in business. Here's what I found from testing. I hooked up the fuel pressure gauge on the rail. Good pressure before cranking and then good pressure after cranking for about 2 mins. After 2 mins, pressure starts wobbling and plummets, and I hear the high pressure pump start whining likes it's empty and the motor dies.

I used a multimeter to test if the low pressure pump is getting power - good there. So, I replaced inline fuel filter, water separator filter, and low pressure pump. I have no idea if those filters have ever been changed, but found no water in fuel. I have rock solid fuel pressure when running at idle on a fake a lake and it's not dying any longer.

Also, pulled vacuum hose while running and getting predictable changes in fuel pressure so I'm assuming regulator is working normally. Will take it out for a high speed test this afternoon.