Wettin My Shorts

My local marine shop just replaced a blown block on one of my 1999 pro max 300. Everything else was replaced also, i.e oil pump, injectors, ECU, anything that could've led to a lubrication problem. Now the first time I took it out, the mechanic and I ran it for 30 minutes at low RPM's for break-in. It started dying and would then start up, run a little then die, as if it were't getting fuel. When we we cleaning plugs with the motor off and we smelled something burning then shut off the battery to that motor. We found out it burned the fuel injector wire and two grounds next to it on the wiring harness and the ECU was split and melted in the back. It also burned up 5 injectors. After mercury sent a rep to the shop and wrote his report, mercury sent another ECU, harness, and injectors. Once it was replaced, the motor ran for 1 1/2 hours and started doing the same thing. Another ECU was torched,(and possibly injectors). While the burned up ECU is still on the motor, the battery was drained in 2 days even though the battery switch was off. And while checking for grounds and voltage on the all the possible wires everything checked out o.k. The motor was still getting an electrical current with the battery switch off. If anyone has any thoughts or solutions please help!

Wally

iTrader: (1)

First i'd check to make sure the switch is wired correctly. If its in the off position....about the only thing that should get any sort of power would be the bilge pumps. Heres what i would do to try and track down your problem.

First dissconnect everything!!! and i mean pull any fuses you may have (just remember to either write down or take a pic of it before hand to know where everything goes back!) Pull the engine harness plug etc...

Next get yourself a digital volt meter and set it to amp readings. Then dissconnect the negative battery cable and hook up the meter between the cables. T this point with everything dissconnected and only the battery switch in place still you shoul dbe able to see if you are getting any sort of draw on the battery. If you do then try a new switch. It may be fudged on the inside. If the switch checks out then start replaceing the fuses. As soon as you install a fuse and it shows a draw then you know something on that circut is useing power....and you can trace it further down from there.
If you suspect its somthing specific then just leave everything dissconnected and just go straight to the source....in you case the engine. Plug the harness back in and see what if any draw it should have. Merc should be able to tell you what the amp draw is for the ECU.......but since they are not learning ECS's and theres no clock or other acc the ECU needs to remember about then there should be none or next to it.

Hope that gives you a good starting point.

Wettin My Shorts

Thanks for the info Wally, I'm bringing my boat back down to the shop and hope they fix it before Memorial!!! Lake Berryessa is waiting!!