Motor Shut Down Filter/Pump/Other
 

I have a rebuilt 454 with approximately 200 hours since the rebuild. I change the oil, distributor cap, fuel/water separator, impellor, carb rebuilds, etc religiously. A recent issue which has been escaping me is that the boat will be running beautiful for around 45 minutes and then suddenly shut down like the key was turned off. What I will do is take the fuel/water separator off and drain it and reinstall to get home and the boat will run beautifully for another 45 minutes or so. Could this issue be the fuel/water separator needing to be changed more often with bad gas in tank or is it a weak mechanical fuel pump which isn’t feeding the bowls fast enough? On a side note the fuel pump is 200 hours old, all fuel lines are leak free and tight, and the key ignition is new.

Thanks again for all the help.

Silly question but have you checked your fuel tank vent?

Usually if it's fuel related,it will gradually lose power,not a clean shutdown.

I would be more suspect of a pickup in the distributor or a failing coil. You are probably giving it just enough time to cool down while fiddling with it.

Not a silly question at all, but the vent has been replaced and is clear.

Boat shuts down litterally like the key was turned. Dump the fuel filter and off again like nothing happened. Oddest thing in the world to me.

I thought the same with the distributor as well. As a test one time when it shut down I started it right back up and idled fine but never get on plane after that. Coil is new, however, because I suspected this and again still doing it. Pickup on MSD ignition is not replaceble only, however, it is only 200 hours as well.

I was assuming thunderbolt ignition. Grab an inline spark tester from a parts store and throw it in the glove compartment until it starts acting up and then install it on the engine. Easiest way to verify if it is a spark issue. I assume you are running an MSD ignition box also?

When you started it right back up ,was it running rich (black smoke) or just no power?

No MSD box being run. When starting back up there was no smoke of any color. It started like nothing happened. This last time it lost power down to an idle. When trying to get on plane the RPMs would go up and then it would stumble. I would bring it back to idle, however, the idle was about 200 RPM higher than it should have been. I shut the motor down (dumped the filter) and off we went with no issues running like a champ.

wonder if a fuel line is being sucked down/collapsing.I'd also check for loose wires under the dash.
your gonna need to start to trouble shoot,,check coil for 12v,,then spark out coil,could be coil is cooling off just as your finishing the fuel filter dump.just a thought.really sounds electrical.