1978 Mercury 900 - Tower of Power - Won't Start

[MichaelCV4]

Hey guys! My buddy and I have been around this forum for a while but finally registered.

We bought a cheap boat off CraigsList earlier this summer from an elderly man who was certain he could get the motor running in a day; funny thing is, it hadn't been started or seen the water in over 15 years! But that was okay because we were looking for a fun project and although we are both have pretty good mechanical aptitude, we have never worked on a boat motor before (only rebuilt vehicles).

Anyways, we have a late 70's 90hp Mercury 900. We have been trying to get it going but can't seem to get her to fire up.

We started by replacing the wiring as it was all pretty dry rotted. We also rebuilt the 3 carburetors, replaced the spark plugs, and got new fuel lines and a filter.

When we crank if with a battery and the key, we get fuel on the plugs and we do have compression. We thought we had spark but when we did the test for the trigger/switch box/coil we realized that with the trigger hooked up, we don't have spark. But we do have spark when we bypass the trigger.

Below are a few pictures and a video of our project and the engine. Any advice or suggestions would be great! Thanks guys!

 

[fastjeff]

First of all, you're lucky it didn't start or you'd be looking for impeller pieces throughout the power head! (Change that sucker now.)

Not sure what you're doing messing with the trigger coil. Motor should not make spark without it--not timed spark, anyhow.


You need to check all of the rotted. replaced wires to be sure they are all there and correctly. The trigger and ignition coils can be tested for continuity with an ohm meter, but the switch boxes require specialized equipment.


Jeff

PS: Great engine! Don't give up.

 

[TrevorPDX503]

I need the wiring diagram for the starter assembly

 

[TrevorPDX503]

I have a 1978 mercury 900 90hp 2 cycle outboard motor and the wires are all corroded and so I got a whole new wiring harness and need a picture or diagram of where the new wires go. Thank you for your help sincerely
TrevorPDX503

 

[Quicksilver]

Distributor style.