MP 350 blowing fuel pump fuse

[ripnlips1]

I have a Marine Power 350 and it's fuel injected. There is a 10 amp fuse for the fuel pumps that blows when I immediately turn the ignition key on. Normally when you turn the ignition key on you hear the low pressure and high pressure fuel pumps cycle but now all I hear is the 10 amp fuse pop. I thought it might be caused by low voltage from my old batteries so I replaced them with brand new fully charged ones. The fuel pumps cycled a few times with the new batteries but now continue to blow when the key is turned on. I'm sure there is a short somewhere or could one of the fuel pumps need to be replaced? Anything else I should check? I have 780 hours on this motor and everything is original.

Thanks,
Mike

[Boat Doc']

Originally Posted by ripnlips1

I have a Marine Power 350 and it's fuel injected. There is a 10 amp fuse for the fuel pumps that blows when I immediately turn the ignition key on. Normally when you turn the ignition key on you hear the low pressure and high pressure fuel pumps cycle but now all I hear is the 10 amp fuse pop. I thought it might be caused by low voltage from my old batteries so I replaced them with brand new fully charged ones. The fuel pumps cycled a few times with the new batteries but now continue to blow when the key is turned on. I'm sure there is a short somewhere or could one of the fuel pumps need to be replaced? Anything else I should check? I have 780 hours on this motor and everything is original.

Thanks,
Mike

Unless there is a pinched wire you probably have a bad pump. You should be able to unplug them one at a time to isolate which one it is

[fishin"G"man]

+1 on replace the fuel pump. Test it by hooking it direct to the battery but have a way to disconnect it quickly. If it runs like a champ then look for a pinched wire that shorts to ground.

[#1stunna]

Ours would blow that same fuse only sometimes when we hit a wake or had a rough ride, we found a small wire that was shorting out, not sure what the wire is to but on ours that wire is super small diameter, was really hard to see the short

[ripnlips1]

Here is what is happening. My original batteries were old (about 12 years old, always on a battery trickle charger when not in use), so they were not putting out enough volts/amps. when the batteries were run down, the fuel pump fuse would blow. I put a 20 amp battery charger on it and while charging, i would turn the key and both fuel pumps would cycle and the engine would turn over and start. With out the charger on the batteries, the fuse would blow. So, I replaced one Odyssey battery (the only type that will fit the tiny battery compartment) with a new one (I will replace the other one soon). The new battery has a manufacture date of 7/11. I installed it, turned the key, and the fuel pumps would cycle and the engine would start. I did this a few times in my garage to make sure the new battery fixed my problem. after the 4th or 5th time I started the engine the fuse started to blow again. Remember the battery was sitting on the the shelf at the store for about a year so it wasn't fully charged. So on the 20 amp charger it went. Now fully charged, turn the key, fuel pumps cycle and engine starts.
So I believe my old worn out high pressure fuel pump blows a fuse when not enough current from my battery is available. Looks like I will be replacing my high pressure fuel pump ($350), low pressure fuel pump ($110) and another Odyssey battery ($212). Not too bad considering that this is my only failure in about 800 engine hours.

Thanks for everyone's input.

Mike