1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

CamoBabe21

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I'm helping my husband work on this boat that has this motor on it, not entirely sure what is wrong with it, but from what I know it will crank over but not fire. The spark plugs have no spark. Basically he is rewiring pretty much everything, he thinks he might have got some wires crossed when he tried starting it the first time, but then found a wiring diagram and wired it the way it showed, but still no spark. We then thought it might not be getting a good connection so we checked all the voltage and what not, but still could find nothing wrong. So then he thought it might be the rotor (not sure if spelled correctly) so we took that apart and cleaned it all up, got a faint spark but not every time we cranked it over. So does anyone know what might be causing the motor to crank but not fire? And if you need more information just ask and I will find out and give it to you! Thank you all in advance.
 

bruchester

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Apr 8, 2013
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Re: 1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

Got this from a poster a week or two ago to troubleshoot no spark condition. Ran these tests, after a bunch of other troubleshooting and decided on bad trigger. Spent the money, installed, motor fires. Still have an issue but it runs.........Brian

Compliments of poster who was very helpful...

Re: Ignition Trouble with 1971 merc 135
I'd bet on the trigger, the rate of failure on triggers is much higher than that of CDI switchboxes.

Here's a test which should help you confirm the problem:

"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."

BTW if your 950's ign has 2 wires coming out of the distributor, connecting to a single terminal on the switchbox, it won't work with the later-style CDI ign. You need a 3-wire distributor to fire the newer CDI switchboxes.

If your 950 does have a 3-wire trigger, it'll fire the 1350's switchbox, but the above test completely bypasses the distributor anyway.

If your 1350's ign system fires with the distributor bypassed for the test, it's a 99.9% certainty that the trigger assy is bad. I've seen new trigger assy's on eBay around $275.

HTH.............ed
 

CamoBabe21

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Re: 1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

Thank you for the information, but my husband says that none of that makes sense. He thinks someone might have put a different ignition on the motor. If it helps any the model number on it is 4D-3. It also says Kiekhaefer on it.
 

CamoBabe21

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Re: 1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

Correction! The year of the motor is not 1974, but a 1960. The serial number on the motor is 1362432. Model Merc 400 EL. Still have no idea whats wrong with it.
 

bgc

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Jul 13, 2011
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Re: 1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

Shes a Cloud White Merc ?

1.Check the tilt cutoff switch on the side of the exhaust cover (port side of block) there should be no continuity when the motor is vertical.
2.Disconnect the "kill switch wire"
3.Check the timing belt at the top of the distributor
Check for spark.


If still nothing pull the magneto/lower distributor and inspect the condenser, points, cap, rotor, and coil (replace the condenser while you're in there, cheep insurance).

There is not much to the early ignition systems but like all of them, each part must be in good condition.

Also, the folks on site below work on nothing but "Old Mercury's"
http://johnsoldmercurysite.com/phpBB3/index.php?sid=e975560b06bebd2c813ee6e4eff8f85c
 

CamoBabe21

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May 30, 2013
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Re: 1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

So we figured out that the coil went bad. Now we are trying to find parts. We need to find a rotor, the part number on it is 394-1108 but I have yet to even be able to find that number anywhere let alone a rotor. So if anyone knows where I can find parts that aren't going to cost me an arm and a leg that would be great :) thanks.
 

CamoBabe21

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May 30, 2013
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Re: 1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

Ok guys I need another part....I need a water pump kit, but I'm not sure what the part number is so I can cross reference it when needed. I've looked and looked, but I guess I'm just looking in the wrong places or something. If anyone can direct me to a water pump kit for my motor that would be great!
 

CamoBabe21

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May 30, 2013
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Re: 1974 Mercury 400 40HP 2 stroke 4cyl Outboard - Won't fire

Now I need to know how to get to and reinstall a new pump. Sorry for any misspelled words. I'm typing off my phone.
 
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