I have a Problem with my 1985 Wellcraft 260....Please Help?

Question

it has the Mercruiser 260HP v8 motor (gm350 i believe?)... The other day we took it out and Weird things happened... 1st when we were cruising the RPM gauge started dancing up and down for a couple seconds? THen later on while on the way back home while cruising Everything just shut off (motor, power, etc.) and the motor wouldnt start or turn (as if all power was Off)...we glanced over a few things like batteries, and switches/fuses but didnt adjust/replace Anything,,,,And a few minutes later it started up again and got us home?

What can my problem be?

Maybe old existing gas, mixed with the new 20gals i put in that day?, Maybe electrical? Please Help

Answer 1

Sounds like a bad ground wire or a short, Gas won't make your gauge's dance.

Answer 2

Sounds like a bad ground on your battery negative post. When you said

"and the motor wouldn't start or turn (as if all power was Off)...we glanced over a few things like batteries, and switches/fuses but didn't adjust/replace Anything"

Did anything turn on such as lights, stereo? If not, your problem is in either the ignition switch or the negative side of your electrical system. Start it in your yard or where ever you store it, make sure to have a  water source for cooling and start wiggling stuff like the ignition switch, negative post of the battery etc.

Good luck!

Answer 3

wiring.  go through all of it.  ignition switch first.  any signs of loose or corroded wires?  then the battery cables...everything that hooks to it.  then the harness (main) plug.  check the wires on the starter.  there is a fuse usually (a cream colored square piece) at the starter...check it.  good luck.

Answer 4

One answer I havent seen and is common. A bad tach can be the problem.

Go back to the engine and find the coil look on the negative post for a grey wire .Diconnect it and place the other wires back on . see if it starts and if it does leave disconnected to use the boat till you get tach

Answer 5

Sounds like an electrical problem. It could be your kill switch on the controls. It's the switch that you are supposed to clamp onto the driver. If you happen to get thrown from the vessel than this will cut all power to the motor and kill the engine. Your ground wire could have corroded and not making good connection. Good luck

Answer 6

With the loss of  power check the battery connection & on the battery disconect as they go bad with corrosion inside>

Answer 7

Troubleshooting these gremlins call for a good mechanic with experience and the time to do it. 1985?? It's like having a hole in the boat and passing money thru it-- But I think a cable is bad--probably corroded and just not providing adequate electric on a sporadic basis--but this will not get better--so get it looked at. The clue is the loss of all power--so the switch or the cable or both are in need of repair. Don't go out again until it is fixed