2000 Bayliner Capri - 5.0 Mercruiser 5.0 Mercarb - Electrical Issues

Garrett13

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Hello Everyone, its my first post on here but ill try to provide the most details to what's happening to me. Yesterday I recievied my boat back from the shop to have my compression issues fixed. We took the boat out and it ran like a dream for an hour and half. Afterwards we were on the back to the dock and first I felt a sudden drop in power, but things picked back up and we were cruising again. Shortly after everything turned off, and the 15amp fuse for the ignition blew. So I tried a few of them and they kept blowing so I went up to a 30 amp, the boat would crank but not start. Then I wondered if it was just out of gas even though the gauge showed a 1/4. We had the boat towed back and went to the store on the way home and filled it up. The next day, I tried troubleshooting to see If I could figure it out. I checked all the connections on top of the motor and could not find any that would cause it to blow a fuse. I did use the multimeter and determine that the plug for the fuel pump is only giving 7 volts and that the fuel pump will run the boat just fine when hooked up to an external power source. Should I just wire a relay for the fuel pump and drive it like it is, or should I keep searching for what's causing the issue? I tried to find the hidden 15amp fuse but could not find that. I also tried to find a fuse for the fuel pump relay but I don't believe I have one. My engine serial number is 0L619688, I have the Two barrel Marcarb also.
 

alldodge

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15 amp ignition fuse blows and you install a 30 amp

hidden 15amp fuse but could not find

If your thinking the fuel pump has a fuse, it doe not

fuel pump is only giving 7 volts

When this was measured was the fuel pump connected, or disconnected and measured at the plug?
 

Garrett13

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I saw on a few posts there was a "hidden" 15 amp fuse somewhere behind the engine and that's what I was referencing. I disconnected the fuel pump and used the multimeter in the wire harness to measure the 7volts and that was while I was cranking the engine.
 
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alldodge

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OK, this means there is something which is drawing to much current. The hidden fuse discussed in other threads are referencing the ignition fuse which yours is not hidden behind the helm

If you still have the 30 amp fuse in where the 15 was I would change to no more then 20

12V comes from the red/purple wire on the key switch thru the ignition fuse. From there it goes thru the key switch to the purple start wire or the Yellow/Red wire for starting.

Disconnect things like the coil, gauges, alternator and then place the 15 amp back in place. Then connect one thing at a time until it blows
 

Garrett13

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Do you have the wiring diagram? I tried searching but can't determine if its the right one for my boat or not! I mean for now could I hook the fuel pump to the ACC switch if I use a relay and fuse?
 

Garrett13

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I think I have figured out the issue but just would like a second opinion on this as I don't want to waste the money on parts. I started to think what if I could run the fuel pump on the acc circuit so I ran the wire, and the fuse blew. Then I wondered if /I hooked it straight to the battery with a 30amp fuse by itself and a switch, the fuse blew again. The fuel pump did run on a battery charger so I thought it would run, but obviously not. Tonight I had someone crank it and the boat would crank with it unplugged but as soon as I plugged the fuel pump in, it would die. Would this make sense on blowing the ignition fuse if the fuel pump is bad?
 

alldodge

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hooked it straight to the battery with a 30amp fuse by itself and a switch, the fuse blew again.

if the fuel pump is bad?

The pump draws no more then 5 amps, it blew a 30 amp, so its bad

This is a 4.3 but its the same as yours

4_3L elect diag.jpg
 

Garrett13

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Well I thought the problem was fixed. I bought a fuel pump for it, started right up and took it out on the lake and went for about 45 mins before that one died. This time though it didn't blow the fuse or anything so it would crank but it just wasn't getting any fuel, verified this at the house the next day. Then I went out today and bought a 300$ one from the boat shop that was quicksilver brand and it still will not get fuel to start. Would the next thing to change be the oil pressure switch?
 

alldodge

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This time though it didn't blow the fuse or anything so it would crank but it just wasn't getting any fuel,

First verify the pump is running when motor is cranking.

If the pump runs then the pump is good and there is a clog somewhere.

Start with a gas can and length of gas line. Place the line in the can and see if you can get fuel to the carb.

If your able to get gas to carb then its either the pickup tube or the antisiphon valve

If your not able to get gas with a can then its clogged in another location
 

Garrett13

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I just ran a test on it, I unplugged the new Fuel pump and plugged the voltmeter in and I was getting the full 12 volts to the fuel pump when cranking. I then even hooked up a battery to the fuel pump and it ran perfect when it got the power from a battery charger? I feel like that test with it running on the other battery shows its not the fuel. I had a full tank when I went out on the water with it and was only out 45 minutes or so.
 

alldodge

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OK pump is running but its not moving fuel. The pump should be ok, need to find where the clog is

I feel like that test with it running on the other battery shows its not the fuel.

If there is no fuel at the pump then the pump won't pump it
 

Garrett13

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I agree, but I hooked a battery up to the terminals of the fuel pump and had it run separately then the engine and it started up just fine! I can't hear it running when connected to the battery harness and that's when I believe its not running.
 

alldodge

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I agree, but I hooked a battery up to the terminals of the fuel pump and had it run separately then the engine and it started up just fine! I can't hear it running when connected to the battery harness and that's when I believe its not running.

This info changes things.
So now use a jumper across the oil pressure switch so pump runs when key is turned ON. This takes the oil switch out of the equation.

If motor runs without issues then its the switch or the electrical connections to/from the switch
 

Garrett13

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So place a wire connecting the two wires to the oil pressure switch? Port side near the rear and oil filter correct?
 

alldodge

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So place a wire connecting the two wires to the oil pressure switch? Port side near the rear and oil filter correct?

Yes, your switch should have 2 wires on it. You can pull it off the switch and jump the 2 wires together. Doing this will turn the pump ON when the key is turned ON and will keep it on when starting
 

Garrett13

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Just did it and heard the pump start just fine and it even cranked up, so I’m guessing the oil pressure switch?
 

Garrett13

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Okay, I did that and the fuel pump ran and it started just fine! So, Im guessing I need a new oil pressure switch? Didn't mean to post it twice.
 

alldodge

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Sure sounds like that is the issue.

When it stopped after 45 minutes, did it ever start back up when cranking?
 

Garrett13

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Nope, it would stay off! The thing that confuses me about that is that doesn't the starter power it when cranking and then the oil pressure switch power when running? If Im getting the 12v when cranking and its not starting then, why does it start when jumping the cables?
 

alldodge

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Might be the ground side of the pump. Power comes from the start (pur/yel) and run (pur) wires but they both use the spliced ground on the other side of the pump. If the pump is jumped directly to the pump contacts, then the motor ground is not used

With it not starting when cranking, then it may just be the ground side
 
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