Engine Cranks but No Start

[jrsick]

2006 Mercruiser 5.0 Alpha 1, carb.
I'm getting good spark, I've tested with an HEI plug tester.
Carb is squirting fuel from the discharge ports when I pump the throttle. I've also added a little gas from a bottle and also tried starting fluid.
The engine can't muster any kind of fire, or even stumble, to give hope.
I'm running out of ideas now and would appreciate your inputs.
Do you think a slow starter could lead to my problem? I estimate the starter is turning the engine at about 12 RPM. Seem slow but I thought I would get a kick with the starting fluid.

[Phillbo]

Confusing at best... The fact that you are getting spark should rule out the kill switch BUT..... check it any way

[mmwjr]

Have you checked the spark at the plugs? A bad distributor cap or rotor can prevent it from reaching the plugs as well as bad wires. Try cranking at dusk to see if any sparks are visible from it jumping off the wires. New caps and rotors have been know to be bad.

Is she cranking slower than before when it ran? All this cranking could wear the starter out.

[Farmer Ed]

I had the same problem last fall with oour 98 maxum 3000.
A new kill switch fixed the problem.
hope this helps

[jrsick]

Thank you for the responses, I appreciate your inputs.
I hear you on the kill switch. I'm going to the boat Thursday and will pull the black/yellow wire from the kill switch to eliminate it as a potential problem. If I get a start I'll reconnect the wire and see if motor stops.
I'm also going to check the ignition key for correct continuity at "run" and "start".
I did run the starter a lot this spring while troubleshooting a carb problem. She is cranking slower. I count about 12 RPM on start and have read where 200 RPM is normal starter cycle speed. I'm going to remove the starter and have it tested. I"ll probably replace the starter as long as I have it out, but am curious if starter is cause of this lingering problem. Battery is good, though I haven't done a voltage drop test yet. Also on list for Thursday. I'm leaning toward starter as problem but keeping open mind.
I have checked spark at the plug with an HEI tester. It's a nice blue spark that has to travel a long way to register on the tester. I feel good about the spark.
Thanks, and keep the suggestions coming.

[jrsick]

Here is pic of my handy HEI tester showing spark:

[mmwjr]

Originally Posted by jrsick

Here is pic of my handy HEI tester showing spark:

You would not get that spark if the ignition switch or kill switch were bad. Right now I think the starter needs to be replaced before you will be able to perform any more troubleshooting and it may do the trick.

[jparsons121]

Fuel - check
Spark - check
Timing?

[jrsick]

Originally Posted by jparsons121

Fuel - check
Spark - check
Timing?

I did replace the distributor cap and rotor recently. If no fire with the new starter then I will need to check timing. The #1 cylinder is easiest to reach on my 5.0, so if the timing is off I should be able to get it close enough to start (providing the timing chain didn't jump a sprocket).
I'm putting a lot of faith in the new starter.

[jrsick]

Problem solved, issue was likely fouled plugs.
I took a look at the number one plug, it smelled like gas and was black and wet.
I decided to replace the plugs since I was going to remove them anyway to dry them off. Engine started right up with new plugs.
Almost certainly caused by me trying to prime a faulty carb with gas. You can tell from the picture I waited too long to change the plugs.

[mmwjr]

Great! Thanks for letting us know. Did you also replace the starter?

[jrsick]

Yep, new starter. Turns the engine 3 times faster than the old one. I think slow starter was part of the problem also.

[gmc60]

Fuel - check
Spark - check
Timing?