Merc. 115 weird electrical problem

First post here..looks like a nice forum.<br /><br /> I have a '76 Merc. Model 1150 that has a weird electrical glitch. The last time we had it out last season, it died suddenly just as we were loading it and wouldn't start. I put it away for the Winter and didn't think much about it. I had just bought it and it had been a touchy devil to start, so I figured I had flooded it or something.<br /><br /> I went to fire it for the first time yesterday, and it won't even pop. Here's the weird part...when the main + battery cable is connected to the battery, you can feel a small electrical charge (shock) when you touch any metal part of the boat/motor. The two other power wires that go to the + side of the battery are not causing this, as I tried them one by one.<br /><br /> The cable I am speaking about is the main cable that runs back to the motor and attaches to a round black solenoid-looking affair. I'm real familiar with automotive stuff, but a novice in boats.<br /><br /> Any ideas? Help! Thanks in advance! -Al

Re: Merc. 115 weird electrical problem

Al, It sounds like you have +12V on the engine block, and you are completing the circuit to earth. This is basically a short circuit.<br /><br />I recommend you check your rectifier. I expect that one of the diodes has shorted, allowing +12V to run to ground. <br /><br />You can get a replacement rectifier at a local Radio Shack for less that $5. Buy the "25 Amp full wave rectifier" and replace the currect rectifier. You will need to ground the negative DC teminal, and change all the connectors on the two stator wires and the positive 12Volt wire.

Re: Merc. 115 weird electrical problem

Chris1956: Thanks so much for the help. I picked up the rectifier assy. you mentioned at Radio Shack. Here's where it gets weird(er) :<br /><br /> I took the old unit off to have a look and noticed that the terminal nut on the terminal with two wires (white and brown) was slightly loose. I tightened it up, rehooked the + cable to the battery but didn't remount the rectifier..just to see if the short was still present. To my surprise..it seemed fine. I remounted it and all seemed okay. I checked the plugs for spark, hit the key and it was running. <br /><br /> Ideas? I thought I might buy an OEM replacement rectifier and install it just to be sure, but the exploded views on ishopmarine.com doesn't look like my unit. Hmmmm?<br /><br /> I look foward to your comments. -Al

Re: Merc. 115 weird electrical problem

Al, The OEM Rectifier is connected to two yellow wires from the stator under the flywheel, and a red wire which is the +12V charging wire. The brown wire on the rectifier is the sender for the tachometer which connects to the round rubber plug on the front of the Merc Control unit. The only white and brown wire combination I can think of is on the Port side of the Switch Box, and these connect to the trigger in the distributor.<br /><br />Before you buy or install a rectifier, check the battery to see if it is charging. Start the motor on the earmuffs and test the battery voltage with a voltmeter. if the battery voltage rises when the engine speed increases, the rectifier is OK. Also check for AC voltage at the battery, by using the AC setting on the voltmeter. if you read AC voltage, the rectifier is bad.