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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10620
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 2008 bayliner 185 with 4.3 merc. Was running on the

Customer Question

I have a 2008 bayliner 185 with 4.3 merc. Was running on the water fine all day until the engine just shut off. The 20 amp fuse on the back of the engine popped. I replaced it and could hear the fuel pump running with the key in the off position.
I returned to the dock and the boat would not die unless I pulled the fuse going to the fuel pump on top of the engine.
Any idea on what part I need to look at changing out?
Thanks,
Rbook
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. My name is***** get the engine serial n umber please? Do the instruments stay on with key off?
Customer: replied 1 year ago.
SN 1A307814All instruments are off when key is off.
Expert:  Tan replied 1 year ago.
Swap the relays does the fuel pump still run.
Customer: replied 1 year ago.
What relays do I swap? Where are they located?
Expert:  Tan replied 1 year ago.
Ok you are going to have only the one relay. Give me a minute to get the engine wiring diagram up. The serial number says this is a carbureted motor correct?
Customer: replied 1 year ago.
That is correct, it is carbed. There is a sensor or relay by the fuse on top of the engine. When I pull it the pump no longer is running. I have no idea what the part is.Another question, should the boat run with the fuel pump fuse on top of the engine still run? Because it will run without the fuse.
Expert:  Tan replied 1 year ago.
Disconnect the purple wire from the alternator. Does the fuel pump continue to run? The engine shouldn't run with fuse removed. But it might be running on the residual fuel in the carb. Disconnect the purple wire from the start solenoid on the starter. Does fuel pump continue to run?
Customer: replied 1 year ago.
It would run with both wires disconnected at the same time or with each other plugged up.
I even tested the purple wire going to the starter and with a hot wire and it would pump also. It would even pump with the fuse pulled from the top with the purple wire from the starter.
Expert:  Tan replied 1 year ago.
Hold on.
Customer: replied 1 year ago.
There is a diode assembly that if it were to go bad then it will allow the engine to stay running. The diode assembly looks like a red fuse holder, part number 83-865913A01. If the problem seems temp related, then the chances are even higher the diode is bad.I believe this may be my issue also. Will see if I can pick one up locally tomorrow.
Expert:  Tan replied 1 year ago.
That was going to be the next check. I found the wiring diagram finally. If you pull the diode this should eliminate that as a possible cause. You can also check the diode. Use your ohm meter connect the leads and read the meter then reverse the leads. The diode should read in one direction and not the other. Keep me posted.

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