Late 70's Mercury 900 Outboard - Won't Start

[MichaelV]

Hello

My buddy and I bought an old '68 Larson back in May and it came with a Mercury 900 Tower of Power. We have finally gotten around to working on it and can't seem to get it started.

Here's what we have done to it:
- New spark plugs
- Replaced the rotted internal wiring
- Rebuilt the carbs

We have watched youtube videos and gone at it with a multimeter but can't figure out why it wont start. It has spark and it has fuel (you can smell it coming out of the exhaust and leaking back out the carbs.) We just can't figure out why it won't fire up. We are both college students and don't want to pour a fortune into it; we are both mechanically apt and have rebuilt car engines from the bottom up but this is our first boat. Any and all advice would be greatly appreciated.

HERE is a link to a previous thread we had with advice on just checking it out.

Below are some pictures and a video of us cranking it for the first time. (not sure why some of the pictures are sideways)

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[Chris1956]

Well, If you have fuel and spark, and she will not run, the timing is suspect. Have you set or checked it?

One more thing, the fuel pump has a diaghram that pulses as the crankcase does, to pump fuel thru two one-way valves, If it gets a hole in it, raw fuel will pour into the crankcase, possibly flooding the motor. Also, choke the crap out of the motor when starting it. The fuel is 50::1 gas to oil, right?

 

[MichaelV]

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We have not messed with the timing at all. We have tried choking it with no luck. And yes we are using mixed fuel. Please see the following pictures. We are trying to figure out what the 'mercury switch' is and why we don't have one. And maybe if we need to jump it somewhere or ground it. Any advice would be appreciated. Thanks!

 

[MichaelV]

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[MichaelV]

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So we made some progress in figuring out what we have and why it won't start.

We tried to time it (link and sync), but we are not getting any spark.

We bypassed the trigger and got spark (which we think means the switch box and coil assembly are both good).

Then we re-hooked up the trigger assembly but are not getting a spark anymore. Does this mean that our trigger is bad?

We are getting fuel on all of the spark plugs after cranking the motor over with the battery. We have compression and air, just no more spark.

What do you guys think, any advice would be great!

 

[MichaelV]

Updated the above post, unfortunately it didn't bump it. Please see above.