1977 evinrude 55 horse

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Mgraff00

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On a cold start my motor runs great. I can motor around the lake without a hiccup. After I get to my fishing spot and shut the outboard down it will restart immediately if I try. If I let it sit though it's like it heat sinks and won't run. It will crank but no start. Occasionally when it does this I can prime it with fuel or start fluid and it will start and run. Most times though priming it doesn't help. I fear that it's losing spark but it's hard to test cause by the time I trailer it home it will start up in my driveway. Any ideas or experiences with this?
 
What is the known history of this engine?
How many times has it been overheated or do you know the complete history? Tons of hours or lightly used? What is the compression?
Give me a run down on what you know and I will get into it. Held off..... but what the heck.
 
Don't know much about it honestly. I do know the older fella I bought it from swore he was religious about changing the impeller every spring. Under the hood looks clean. I've seen hot stern drives with bubbled or melted paint and this don't seem to have any. Skeg looks new and boat is in decent shape don't really think it was abused
 
There are a few things that can/will cause what you are describing.
You observation of heat soak will be the first issue to cover.
A typical heat soak situation manifests itself on a hot day. This is aggrevated when a portable tank still has Winter blend fuel in it. Is this possible in your case? Does the engine not do this during the colder months?
What is a heat soak? Heat soak normally occurs after an engine (outboard in your case) has been run on plane for a while then shut down. If left for a period of around 20 minutes or so the fuel in the bowls will be the same temp as the engine. The engine has actually increased in overall temperature as well since you shut it down so the fuel is very hot. Add to that the fact that the inside of the cylinder and crankcase is very dry as a result of the on plane run. Now, you try to start the engine. Hard to start and usually will not accelerate once started are the normal observations of heat soak. Your idle and high speed circuits in your carburetor work off of Bernoulli's principal hence the venturi in your carburetor. Once vacuum from the venturi is applied to the lift tubes inside your carburetor the boiling point of the fuel immediately drops and you are now pulling atomized fuel or fuel vapor through the lift tubes instead of solid fuel and air bubbles that make up the needed emulsion. Remember that a liquid bois at a lower temperature when a vacuum is applied or at altitude? Engines will not accelerate on this without engaging the choke or primer liberally. Once the fuel in the bowl has cycled through and been replaced by cooler fuel the engine will accelerate. This may also be the reason why you can do your immediate restart once shut down as the fuel has not gotten hot yet. Moving away from alcohol extended fuels will help some in a situation like this and covering your fuel tanks to get them out of direct sunlight helps a little as well. Go and try this and see if this is what you are experiencing.
There is another issue that may be causing what you describe that is common to older 2 and 3 cylinder loopers that can aggrevate what you are seeing or be the sole cause as well but lets start here first.
 
Not a vapor lock issue. Very familiar with that. I see it often on small blocks in small stern drives. What I'm finding is after it sits and heat soaks is I'm losing spark. I don't want to just throw parts at it. Since I'll be using this for duck hunting this winter I want it to be reliable. I'm great with inboard/stern drive engines but these older evinrudes frustrate me to death.
 
You will need a peak reading voltmeter to properly check the ignition system. Something like a Stevens CD-77 or Merc-O-Tronic.
Why didnt you tell me you were losing spark when hot. Fingers were tired from typing all that info on heat soak.
You can always take the engine to a good dealer and have them run the numbers on the ignition system for you. Make them write all numbers down instead of just telling you "Its the pack". Almost every ignition component in the ignition system is capable of breaking down with heat so there is no definitive way to guide you.
Or if you wait around here long enough you may just get an answer like "Its the coilpacktimerstator because my buddy's engine is the same one and it did that"
 

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