I have a 280SS with a Merc 496/Bravo...

[Cary1]

I have a 280SS with a Merc 496/Bravo 3 and it shuts off after it runs for about an hour and unable to start until it cools down and then starts right up and runs good for about another 45 minutes or so. does anyone know the cause and fix?

[CaptainK]

check for vapor lock, if you have the cool fuel pump module on the side of the motor a raw water line cools the fuel. This happened on my 496's on a 340 sundancer. Took 10 minutes to fix and clear the line.

[Cary1]

great 10 minutes to fix .... what do I do to fix

[Callies_Choice]

You didn't mention the year of the boat. If it is carbureted and has a distributor it is most likely the pickup on the mounted under the top plate. They are known to fail and the symptoms are as you describe. They work well until they get hot. It is not a simple filx as the distributor must be removed.

[Janay]

Writing this for my husband - we own a 2005 340 Dancer. 8.1 496’s Gen 3 cool fuel pumps. It will support 50-60 PSI’s fuel pressure - at idle speed approximately 25-30 minutes in, fuel pressure drops to 5 PSI’s, all at idle speed. - both engines die completely. Cruising speed runs great! Any ideas or suggestions as to what might the problem be? In advance all help appreciated!

[baby]

Cary Had the same thing happen our boat , Had a 5.0 Merc with throttle body fuel injection. It was a 2001. Sounds it is vapor locking when you throttle back. After 16 breakdowns and 3 mechanics later the solution was an extra fuel boost pump, never happened again. Take to a good Merc marine mech.