Mercruiser Horizon died while running under full power and will not start

[gantone1]

Engine: 2007 Horizon 8.1 375HP with 270 hour
Drive: Direct drive Borg Warner Velvet Drive (Inbourd)


Engine was running strong at full power for 5 minutes, then put in neutral and let it idle for 5 minutes while I set up my VesselView app. After that I was bringing it back up on plane under full power when I lost power almost like I ran out of gas. It will not start though as I crank it sounds like it is wants to start.

I checked my water separator and it is full of gas (and no water) and I have a quarter tank, I have run it to E in the past without running out so I think my gauge is trustworthy.

When I turn on the key, I hear what sounds like a fuel pump run for a moment. I did not get any alarms

Do you have any suggestions?

Thanks!

 

[jimmbo]

I will assume your engine is Fuel Injected, well that make trouble shooting a lot more difficult, the computer and all. Wiggle and/or disconnect and reconnect all wiring harnesses. Does it have a driver overboard lanyard/switch? Try activating/resetting it.
Have you tried spraying some fuel into the throttle body? Does it have spark? There is an anti syphon valve that can stick shut, starving the engine of fuel. You could unhook the hose going to the fuel pump and see if it will run from a portable tank.

 

[alldodge]

Agree, check the kill switch or use a jumper to bypass
Check fuses, will be under a thin cap next to relays
Swap the main power relay (MPR) with the fuel pump then listen for the fuel pump to come on
Check power at the MPR
Listen for a light ticking while cranking (fuel injectors firing)

Check to see if the Crankshaft and Camshaft position sensors are in place. Cam is on the timing chain cover, and Crank is at the rear of the block on top port side

 

[Alumarine]

Does the VesselView app show any errors or faults?

 

[gantone1]

This morning I cranked it and it fired up, since it is on boatlift (and I was late for work) I could only run it for a sec, but it sounded normal.

So two things have changed since I broke down.
- The boat sits more horizontal on the lift than when floating, maybe my fuel gauge cannot be trusted.
- The engine is cold, whereas last night the engine was fully warmed up

I better eliminate the possiblity of running out of fuel first. I will take a spare tank and see if it happens again and if so if it is solved by adding gas. Either way I am having my wife follow me in the jet ski to tow me back!

 

[alldodge]

Don't run it for even a few seconds without water going into the sea pump. The impeller will burn up fast

Might be a loose connection. Took mine out the other day, floated a bit. Went to restart and nothing, no click hum, nothing. Turned out to be one screw in my ignition switch was loose