'65 Merc 1000 Just Quit at WOT - Ideas?

[gbeardmore]

On the way back from a full day of boating (a mix of idling and running on plane) we were going at WOT when the motor just quit. It was as if someone just turned off the key.

We limped back to the dock with the trolling motor, as it just would not start again. In the driveway I find it cranksjust fine but I have no spark on any cylinders. So, as a real novice where should I start?

Both coils read 0.0 Ohms resistance on the small posts and 9.7 & 10.5 on the center to small post. Are those normal readings? Any ideas as to what else I can check?

I hate to just hand it off to a shop and pay 100% mark up on parts I could replace myself, if I knew what to be testing and how....

 

[merc850]

Re: '65 Merc 1000 Just Quit at WOT - Ideas?

The first thing I would check is the voltage to the coils, turn the key to "RUN" and put a V meter lead on the red wire of each coil with the other lead to a ground; you should see around 9 volts.
There is a mercury cutoff switch on one side of the motor and sometimes they go bad; disconnect it from the 2 terminal block and see if motor will start.

 

[gbeardmore]

Re: '65 Merc 1000 Just Quit at WOT - Ideas?

Put the volt meter on as suggested. There are 2 coils. The aft coil reads 12.3v, the forward one reads 5.3v.

I assume that implies a weak coil, not a failed coil. Is that correct, or could that have caused the motor to quit so abruptly?

Haven't had the opportunity to check the cut-off switch. Not real sure where it is. I think its time to get a service manual.

 

[merc850]

Re: '65 Merc 1000 Just Quit at WOT - Ideas?

Here's a wiring diagram that might help; you have power to the coils and the difference in voltage is unusual but should not cause total shutdown. I would
check the timing belt under the flywheel (they get old and break) and the rotor in the distributor but remove the side contact first then unscew the bolts that hold the cap on.