Merc 5.7 will only run at speed 15 minutes, but idles fine

[Smoke45]

2001 Tahoe Q7 with Mercruiser 5.7 2bbl, TB5 ignition
Engine Serial 0M003018

I put new dizzy cap, plugs, plug wires on it at the beginning of the season, its been running like a top.

A few weeks ago we headed out and it ran fine for about 15-20 minutes and then suddenly lost power, stuttering and spitting like someone switched all the plug wires. It would idle fine and I was able to limp back running <1200 rpm.

The next day I put it on the hose and it runs fine. I had not changed the coil when I did the plugs and wires so I bought a new coil and installed it. I also dumped and replaced the fuel filter (didn't notice any water), and pulled the fuel line and filter off the carb (it was clean). Also checked the fuel tank vent tube and it's clear.

A few days later I put it back in the water, rode around for 15-20 minutes and it did the exact same thing. I felt of the fuel line and its cool, opened the fuel filler cap, propped the deck up...can't fine anything out of whack but it will only run 1200-1500 rpm until the next day.

Is it possible the ICM or fuel pump heats up and craps out, but then works ok after it cools off?

 

[tpenfield]

The (sensor) in the distributor is a possibility, the ICM itself is a bit pricey, so hopefully it is not that. Also, may be the choke mechanism. See if the engine is choking itself once it warms up.

 

[alldodge]

Its hardly ever the coil, I'm thinking the distributor sensor 87-892150Q02
If it failed it can be tested to find the fault, but with it still sort of working it probably will not show a fault running thru the troubleshooting guide. The new sensors come with a ground lead and yours being a 2001 may already have this lead. The issue was the sensor would loose a ground and start misfiring.

http://www.mercruiserparts.com/bam/subassembly/31867/2697/60