Mysterious engine shutdowns?? horizon 8.1s

[loweman]

I'll admit I am not an engine expert, but this has me stumped so I figured I would throw it out here..

We just had the manifolds and risers etc replaced about a week ago on horizon 8.1 dts on 2010 sea ray...240 hrs ea. Earlier this year all new plugs and fuel filters as they were due.
Anyway first time taking it out after manifold replacement and basically spent about 30 min doing some docking practice, engines running great without a blip. During the last one with the engines at or near idle, the port just shutdown...no smartcraft warnings, horns, and all gauges look good. no restart but turning over ..kept backing and just after the stbd quit as well, again no bad indications.. buddy grabbed lines to secure our unexpected docking and I attempted to restart both with no success..(very lucky it didn't happen crosscurrent in the fairway where we were about 6 minutes previous)

spent about an hour looking for anything weird in the fuel lines to include looking at the fuel valve solenoids off each tank...all appears normal ..

For grins we switched the port fuel valve solenoid to bypass and tried to start to see if it helped, it started...then I tried stbd and it started as well, shockingly, because we had done nothing to the stbd fuel solenoid..so much for that troubleshooting..

Anyway, ran the engines throttle only at medium rpm for a 5-10 minutes and they are humming as sweet as ever, them powered down to different settings finally letting it run at about 800 rpm or so ….near idle as we did during our down current docking..and just let it run....running smooth and great, all is good...until about 6 minutes later the stbd ran lightly rough (like a something running out of gas) for about 2 sec then shut down..Then about 2 minutes later the port did the same thing...tried a restart about 15 min later with no luck as we had to leave...

Of note we have never had anything happen like this and this is the first sustained use post manifold /riser replacement.

2 separate fuel tanks , not interconnected..so cant think of what would cause the same problem on different motors within 2 minutes of each other..

thought??

sigh

thx!!

J

 

[Espos4]

When it cranks but doesn’t start, check for spark.

Also, Do these motors have the cool fuel 3 module?

 

[Korkie]

Check your batteries. Load test them to make sure they are strong enough to supply required juicy to motors. At high rpms your alternator generates the required voltage/amperage needed. At idle, the batteries supply the needed voltage/amperage. They may not be holding a charge, so after a short period of idling, they lose the ability to supply what the system requires. If when your engine work was done your charging system / batteries were not maintained, this would have been enough to kill a set / bank or 2 of batteries already close to aging out. This happened to me 2 seasons ago. Boat dry docked to have work done and not plugged in. Wiped out my strd bank.

 

[PlayDate]

I'll admit I am not an engine expert, but this has me stumped so I figured I would throw it out here..

We just had the manifolds and risers etc replaced about a week ago on horizon 8.1 dts on 2010 sea ray...240 hrs ea. Earlier this year all new plugs and fuel filters as they were due.
Anyway first time taking it out after manifold replacement and basically spent about 30 min doing some docking practice, engines running great without a blip. During the last one with the engines at or near idle, the port just shutdown...no smartcraft warnings, horns, and all gauges look good. no restart but turning over ..kept backing and just after the stbd quit as well, again no bad indications.. buddy grabbed lines to secure our unexpected docking and I attempted to restart both with no success..(very lucky it didn't happen crosscurrent in the fairway where we were about 6 minutes previous)

spent about an hour looking for anything weird in the fuel lines to include looking at the fuel valve solenoids off each tank...all appears normal ..

For grins we switched the port fuel valve solenoid to bypass and tried to start to see if it helped, it started...then I tried stbd and it started as well, shockingly, because we had done nothing to the stbd fuel solenoid..so much for that troubleshooting..

Anyway, ran the engines throttle only at medium rpm for a 5-10 minutes and they are humming as sweet as ever, them powered down to different settings finally letting it run at about 800 rpm or so ….near idle as we did during our down current docking..and just let it run....running smooth and great, all is good...until about 6 minutes later the stbd ran lightly rough (like a something running out of gas) for about 2 sec then shut down..Then about 2 minutes later the port did the same thing...tried a restart about 15 min later with no luck as we had to leave...

Of note we have never had anything happen like this and this is the first sustained use post manifold /riser replacement.

2 separate fuel tanks , not interconnected..so cant think of what would cause the same problem on different motors within 2 minutes of each other..

thought??

sigh

thx!!

J

Definitely a fuel delivery issue as evidenced by you switching the solenoids to bypass. As to why they shutdown within minutes of each other without throwing a code.....that is a mystery. I would probably start with checking the fuel pressure on the injector rail and go from there.

Replacing the manifolds and risers normally would not require removing ground cables or the engine connector. If those were disturbed they could cause what you are seeing but both engines shutting down within minutes of each other is just strange.

 

[scoflaw]

All my relays and ecm are mounted to my exhaust elbow. Maybe a bent pin if they were disconnected

 

[ColoSR]

My engine was doing something similar, turned out to be vapor lock. Ran like a top, then would not restart after I ran in idle for an extended period of time. VV wasn’t showing any codes either.

My 6.2 has a thru Hull intake, but I had my mechanic reinstall the leg intake as well this winter so I could get through our aquatic species Decon stations. If I run on the leg only, the boat will vapor lock. If I run with the thru Hull intake open or run the blower at idle no problems. Apparently the engine “heat soaks” the compartment when running at idle or for 15-30 minutes after shutdown.

CSR posters have recommended to run the blower at idle and for a few minutes after shutdown. You can also dump some cold water on the cool fuel unit and see if it starts. If the blower doesn’t work, but cold water does, mercruiser has a vapor lock service bulletin that recommends the install of a check valve and booster pump to keep hot water from back flowing into the cool fuel and to make sure that the main pump always has liquid fuel in it.