1978 Mercury 900 90HP will not start

[talbee]

I don't know what the heck is going on now.

I've replaced the solenoid, starter, rectifier, switchbox, and distributor assembly.

I've just installed the distributor assembly a few days ago and had my mechanic set the timing to specs. I've ran the boat for 2 days, but now it's not starting. I checked for spark yesterday and there's spark. I've checked voltage and ohms on the other parts and everything checks out fine. I've checked the voltage on all 3 of my batteries and they're getting 12-13 volts.

I don't know what else to do. I'm getting really frustrated with having one issue after another. Please help!!

 

[jimmbo]

Has it got gas?

 

[CharlieB]

Typical Merc 2 strokes LOVE fuel, LOTS of it, or they won't fire.

If this is an old stacked 6 90 HP you have to almost STAND on the choke until it fires before letting go, then be ready to immediately punch the choke again if it falters as if going to die.

 

[talbee]

It's an inline 6. 10 gallons of gas. I've primed it until I can't squeeze the bulb.

 

[Chris1956]

To start that motor. Cold start lever all the way up. Prime it until bulb is hard and pump a bit more, if possible. Hold choke button down and crank her until she fires. Feather the choke until she is warm.

 

[racerone]

Install an OMC electric fuel primer system.---Fairly easy to do.----That eliminates " hard to start " due to fuel / choking issues.

 

[CharlieB]

Many of the old carbs only used a choke plate on the upper two carbs. Nothing on the lower.

This is why we tell you to HOLD the Choke ON til it fires. They LOVE fuel and won't fire a pop without it.

 

[talbee]

Thanks so much for the responses.

One thing I found unusual, when weather reaches 80 or above the motor starts no problem. My carbs are a little dirty. Do any of you think one or more may be gummed up and when it gets hot it loosens up and allows fuel to go into the carb(s)?

 

[Chris1956]

Those motors start easier when the temp is warm, just normal for them. You need to choke the crap out of them when it is cold.

If she idles correctly and accelerates smoothly, the carbs are adequately clean.

 

[Jdeanie]

Might want to turn the idle mixture screws in a turn then back out a turn to clear any junk that could have accumulated around the passageway.
I get to clearing out the cylinders by removing the plugs and cranking motor over to let her breath .
Could cover the bottom carb with something at start up too. Then if all fails put your flywheel to 0 * and find spark by turning the cap.
Look up link and sink on YouTube , cturboaddict he has 75 115 hp but it's same procedure for our motors.
If you could post a picture of you flywheel timing marks I'd be very grateful .

 

[talbee]

I'm subscribed to cturboaddict. He helped me a few times.

Ill get a pic today after work

Thanks Chris and Jdeanie

 

[talbee]

My lync and sync was a little off. It starts just fine now.