1974 Mercury 650 65hp

[dahogman]

I just bought a 1974 Starcraft 16 ft with a 1974 Mercury 650 65 hp on it. I paid $130.oo for boat, motor, and trailer. To good a deal to pass up as I figure I can scrap it out and sell trailer if worse comes to worse. I put new plugs in motor, new fuel bulb, new fuel lines from pump to carbs, cleaned fuel screen, new plug wires, new carbon brush in cap, cleaned cap, flushed fuel tank. I tried to start and turns over but doesn't seem to fire. I even put mixed gas directly in cylinders and no luck. I got my cheapo circuit test and it seems I have no power to coil. I checked with key on and with key off and could detect no power at coil. Should there be power to coil with key on but not cranking? Any help would be appreciated to start me down right path. I have power at the box at at least one terminal.

 

[emckelvy]

Re: 1974 Mercury 650 65hp

Follow the steps in below procedure and you should be able to pinpoint the problem. Be aware that the switchbox on 3-cyl's is arranged a bit differently than the others but the basics of the test will still apply.

HTH........ed

MERCURY BATTERY-POWERED CDI TEST FOR DISTRIBUTOR MODELS

This test is for the 332-2986 switchbox used from 1967-1978 on all the inlines.

This test assumes your coil is good (problems with CDI coils are rare).

DISCONNECT BATTERY

1. Turn off ignition;

2. Disconnect all 3 distributor wires on the Port side of the switchbox (and the ?mercury switch? if present);

3. Remove the HV lead from the ign coil to the center of the dist. cap (remember it unplugs from the coil and unscrews from the cap);

4. Reconnect the HV lead to the COIL only;

5. Position the free end of the HV lead approx. 3/8" from ground (block, shrouds etc), and find a way to hold it there;

6. Jumper the brown and white terminals on the dist. side of the switchbox to each other.

RECONNECT BATTERY

7. Check that you have +12V at the red terminal (even with the ign off);

8. Turn on ignition and verify +12V at the white terminal (same side as the red terminal);

9. Ground the black terminal on the distributor side of the switchbox - this should cause a spark each time you touch ground.

If you get spark with the distributor bypassed, and it won't fire with the distributor connected, the trigger is bad and the entire distributor housing assy must be replaced.

If you get no spark using the test, the switchbox is probably bad. In that case, be sure to check for correct power on the switchbox, check all connections, and check the coil's resistance to make sure it's OK.

But for Inline Sixes from approx '68-'79 with belt-driven distributor (3 & 4-cyl's too except for those with Lightning Energizer ign), the above test will confirm a bad trigger.

 

[cheapthrills]

Re: 1974 Mercury 650 65hp

I have the exact same boat, same motor and same year. Bought it in March, motor ran but not too well. I thought I got a deal at $900, wow you stole it!!

My motor needed carbs rebuilt, timing set and new plugs. Ran all summer and just recently had a problem. It will not charge the battery, but I think it is a rectifier. Maintain the outboard and you should get some serious fun and use out of it. Not a big lake boat, but a fun little flat water boat.

 

[kelbone]

Re: 1974 Mercury 650 65hp

I know this is an old thread, but, if anyone is still looking at how to check the switchbox, try this. Disconnect the gas line and let it run out of fuel. Then, while cranking the engine, check the voltage on the White wire. As long as it is 9.5 volts or more you're good so far. If you don't have at leat 9.5 volts here then there is probably a problem in the switch/harness/wiring/battery. Then while cranking the engine check the white/black wire. You have to have at least 9 volts here. If it is lower than 9 volts, the switchbox is bad. If that checks out OK then check the voltage on the green wire. Be sure to set your multimeter/tester to a high enough DC voltage setting to prevent burning it up. This green wire when you are cranking will put out about 200 DCV. If it doesn't your Switchbox is bad.
You can also put a jumper wire from the white wire to the white/black wire. Then put a jumper on the blue wire. Make the wire long enough you can touch ground easily. Then put a spark gap tester on a spark plug wire and stick the other end of the wire into the coil. After you have done this, turn on the key and then touch the blue wire jumper you made to ground. Don't hold it there, just touch it briefly. Every time you do this you should see a spark. If you see a spark the Switchbox is probably good. if you only have fire on one cylinder then the problem is probably in the rotor button or distributor cap. If you only get spark when you let off the key switch from cranking it, then probably a bad trigger.
Good luck.

Edit: I have the '73 model 650.

 

[sportyinc]

Re: 1974 Mercury 650 65hp

If you are troubleshooting a Mercury switch box, it is because the motor won't run.
How do you run the motor out of fuel when it doesn't run?
Is this step necessary?

Thanks

 

[dahogman]

Re: 1974 Mercury 650 65hp

Drain the carbs!