A stalling and Misfiring after an hour?

[Mandalore]

Hi all I have a Mercedes 5.7lt V8, runs well for about an hour running at 2 -3 thousand revs but after that starts to misfire and stall, stopped engine and let sit for about 20mins and restarted and ran for about 20 fine on lower revs but again misfires and shudders with power losses, pushed on at low revs and limped home. Have recently put in new fuel filter, new plugs, leads seem tight and recently replaced exhaust shutters.

Any ideas what I should look at next.

 

[alldodge]

Howdy

What year is the motor? Have a serial number?
Assuming its a Mercuiser and not a Mercedes

Have you replaced the filter/screen in the carb?

When it does this open the fuel fill cap and listen to see if you hear air rush in

 

[J hickman]

Subscribed to this, I am dealing with similar issues

 

[Mandalore]

Apologies autospell, yes its a mercruiser SN OF155802, havent replaced carb screen replaced plugs, watersep fuel filter about 2 weeks ago, was out this evening for an hour no probs ( kept revs under 2700, seems only starts at high revs and once starts will keep happening even at low revs unless i shut down completely almost like o
Its being starved of juice?

 

[alldodge]

Apologies autospell, yes its a mercruiser SN OF155802, havent replaced carb screen replaced plugs, watersep fuel filter about 2 weeks ago, was out this evening for an hour no probs ( kept revs under 2700, seems only starts at high revs and once starts will keep happening even at low revs unless i shut down completely almost like o
Its being starved of juice?

This is the area of and air leak in the fuel system, a weak fuel pump, anti-siphon valve restriction, fuel line restriction or clogged vent.

Things to check, get it up running until it starts the issue, then remove the gas cap and listen for air to be sucked in.
If no air, then remove fuel filter and see if its full of gas.
If its full then need to put a fuel pressure gauge in line using a Tee between the pump and carb