Have a 1986 Mercruiser 120. Full tune 15 hours ago.(plugs, points, condensor, timed, etc.) Carb rebuild 10 hours ago. Last trip out after at least 1 hour straight run would not start. Cranks fine, but like no gas. Pump twice then like a gallon of gas in the carburetor, i.e. flooded. Eventually starts after a half hour or so, but any hints?

Welcome melsfun, sorry to hear you're having problems. Experts will be along shortly.

Bad coil?

Based on what you wrote:

Possibly three things. IMO:

Vapor Lock: What was the heat outside?

Ignition parts (Condenser) gone bad: (Swap back in the old one to check) or maybe Coil like D-Rod mentioned.

Stuck Carb Float. (Typically not heat related though - check that rebuild)

I don't know your particular engine, but in general engine knowldge, these three come quickly to mind.

Will Check. Thanks

Yeah, hotter than.... Lake Mead Nevada in August. What do you do for vapor lock on a boat besides drink and play in the water:) It will start after it sits which is the cure that I remember. Don't have to worry about that with new engines do we. Thanks much. Checked the coil, seems fine.

Some random thoughts again:

Open the engine cover when stopped. Run the blower/fan. Find a way to protect/isolate/insulate the fuel lines from the heat.

(Again not familiar with your specific model...)

We can do that. This is good. We are getting ready for a house boat trip on Lake Mead the first week of September and as long as we have an idea of what to do, we can make something do something. Bye the way, I'm a girl, so boy help is great.

Let it idle for two or three minutes before you shut down. that will let the cylinder head and exhaust cool some. Run the blower while you are running to pull some fresh air in. A wet towel can be used to cool the fuel line and intake.

And never pour gas down the carb unless you are in your driveway. You can't run to the sidewalk to get away if you catch fire in the middle of the lake.

I am set for fun. I can't thank you enough. I'll let you all know how the hints helped.

Since you say it's flooded after pumping, it's highly likely it was ALREADY flooded--pumping the throttle twice can't flood it if it wasn't but it WILL allow some necessary air in and unnecessary fumes out...

Everything about a tune up is straightforward except the rebuilding the carb part. My guess is the float level was set too high, and upon shutdown, especially in your heat, fuel is gurgling out of the float bowl and into the carb throat. All you need is a teaspoon of gas to dribble into the manifold of that dinky engine and it WON'T start for a half hour...

You might also check your overflow line from the fuel pump to the carb, if there's ANY gas in that line while running, that can cause your problem...