40 hp merc 4 stroke 2008

i turn on the ignition to the mid way point and it blows the 20 amp fuse right away. any guesses what this feeds or what i might check? thanks

Re: 40 hp merc 4 stroke 2008

Check to make sure your battery cables aren't connected up backwards.

Re: 40 hp merc 4 stroke 2008

I drove it yesterday all day and it ran great. Today when i tried to start it it just turned over with no firing. Checked fuses and the 20 amp was blown. Replaced 3 times! And it burns before even turning over motor. As soon as key turns on half way?

Re: 40 hp merc 4 stroke 2008

Try unplugging the fuel pump. Two wire plug on top of the vapor seperator tank. If you can crank it without blowing the fuse while pump is unplugged, the high pressure fuel pump is junk.

Re: 40 hp merc 4 stroke 2008

Hi,
Tried unplugging the wires to pump and still blows the fuse instantly. The top of the 3 solenoids on the back of the engine clicks loud when the key is turned on, could that be anything?
Thanks

Re: 40 hp merc 4 stroke 2008

Disconnect rectifier and retest...

Re: 40 hp merc 4 stroke 2008

Sorry but a brief rectifier look and position description would help me greatly
thanks

Re: 40 hp merc 4 stroke 2008

The relay that is clicking is the Main Power relay, and is normal. Next as Faztbullet suggests is the voltage regulator. Just under and aft of the Vapor sep. tank you will see a 3"x3" square box with black, yellow, red and grey wires coming out of it. Disconnect the red wires and recheck. Two more things though, I believe this year motor has a 20 amp fuse off of the regulator circuit all to itself. Also, depending on your serial number, there was a recall on the voltage regulators on this motor. Post your serial number and I will check for you.

Re: 40 hp merc 4 stroke 2008

Hi,
I found and unhooked the red wire and fried a fuse. Then removed the yellow wire to try it and blew another fuse. This fuse stops the engine from firing. It will still turn over fine just no spark. I have a 06 30 hp 4 stroke merc that from time to time will blow the same fuse when you shut it off. You wouldnt know it till you went to start it again and it would crank and crank but not fire. But change the fuse on it and away you go again. Seems to happen twice a summer on that one. This one is S/N 1C058697 and says built in late 07. The fuse sits in the fuse box on the right front of the engine when looking at it, and the fuse is in the right hand side closest the front.
Thanks

Re: 40 hp merc 4 stroke 2008

I checked your serial number and this motor is not affected by the recall campaign. You motor is under warranty till 12/14/10, so why not get it to a dealer and let them fix it while it's still covered? With the cover off, when you first key into the "run" position, do you hear the electric fuel pump cycle for a few seconds? You still could have a fuel pump issue. Based on what you stated earlier, if you turned the key to the "run" position and the fuse blew immediately, than you have a short somewhere. If now you turn the key on and it cranks but will not fire, this may be a seperate, but related issue. Get it to a dealer and let them chase the isssue. Part of the cost of a engine is the warranty. Why not take advantage of this?