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Engine trouble

Crusader1993

New member
Hello, I have a 1993 silverton running twin 503xl.carb engines starboard engine will run fine for 30-40 min then will start to loose rpm. I can back off the throttle and keep it running. when it first started happening it was once changed fuel filter it was fine This season new filters new rotor cap plugs problem is back runs fine 30 min then starts lose power Switched tanks problem does not move to other engine. Anyone else have a problem like this? I’m thinking the distributor, module was replaced no change
 
MSTS is still connected, I assume it’s working? Not quite sure how to test it.
Fuel filter is full no water present fresh fuel I had thought maybe the oil safety sensor was bad and shutting the fuel pump down so I replaced that. Didn’t help. Could it be a weak fuel pump.tat acts up when it gets hot?
 
maybe....but I'd think checking the other items would be in order.

Have you checked the anti-syphon valve for crud accumulation?
 
Best way to troubleshoot the fuel system is to plumb in a temporary pressure gauge between the pump and carb. Fittings and flexible fuel line is readily available. A combo vacuum/pressure gauge works great. Should have about 7 psi. Had the same problem with a 454XL. When performance dropped off the pressure was also low. At about 4psi the surging started. Decided to check the current going to the pump just to be sure it was a pump problem and not an electrical issue. Put a voltmeter on the power wire going to the pump and noticed it started out at 13 volts and then slowly dropped. The problem turned out to be the oil pressure switch which directs current to the pump after the oil pressure comes up. Changing the switch fixed the problem. The Crusader pressure switches are famously problematic. Careful troubleshooting is the way forward. Good Lucvk.
 
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