Mecury Optimax Problems

[wren]

I have a 2005 Optimax, and started having problems recently. I blew a piston, took the boat to the shop to get redone and neer worked right since. I will be crusing at around 3500rpm's to break in again and all of a sudden the boat starts to jerk and then it shuts down. I put a smartcraft guage in to help me with the problem. I see the volts go from 12.5 to 13 will running and all of a sudden drops to 11 - 9 volts, the engine shuts down. took back to the shop and the mechanic had the alternator redone and also changed another wire. Took the boat out yesterday and the same problem occured.

Purchased a new battery today with 1000 cold cranking amps and volts are still going crazy just as before. I and my mechanic are at a loss.


What is the cuase of this?

[EuropeanAM]

Three things I would recommend checking:

1. Battery cable connections AT THE ENGINE- especially the GROUND cable (which is down below the starter, attached to the block). DISCONNECT the cable here, clean the block surface (until shiny metal), and reconnect. Ensure cable cannot rotate on attaching bolt.

2. GROUND cable connection for alternator. Same as above... clean connection ends and reconnect.

3. Isolate ALL other battery cable connections. Install ONLY the battery cables, DIRECTLY to the battery (bypassing any battery switches). I recently ran across one doing this same thing.... highly suspect the battery switch panel (which was flapping loose without it's retaining bolts inside the back well).

Report back with your results- will be happy to assist more if necessary.

[bilge rat]

I have seen some of the Perko battery switches giving intermittant connection problems. The Blue Seas switches are much more reliable. My experence is more on inshore saltwater boats but if something electrical works there it will work on a freshwater boat easily. The voltage drop is the common symtom seen in a faulty switch.