70hp 1988 Evinrude (sometimes) doesn’t start

[WildGooseRude]

I am having primarily starting issues with the outboard (E70TLCCA). The first day of the season, the motor cut out at full throttle and I had to be towed in. Since then, ran well for 2 additional days (3 hours runtime each day. The next time out the motor would not start at all. Today I went to troubleshoot and it started right up ~6 times, but about 20min later it would not start at all.

Here is what I know/ have troubleshot:

• Spark was tested with screwdriver and all 3 were functional. I would like to also test with a tester to see if there is spark when it is not starting
• Spark plugs wet when I pull them out. Nothing visually odd about the them
• Gas line is brand new
• Bulb is fairly firm but does not get extremely firm like I am used to on outboards
• Impeller has 15 hours on it, have steady stream out when running
• neutral safety switch looks to be mechanically ok
• No loose or damaged wiring found
• New gas, older oil

Any ideas, or help on what to check? I plan on checking compression tomorrow. My guess was spark issues until that was tested today. Truthfully I may have flooded the engine by testing start so many times, but that does not explain the other instances of this issue

 

[WildGooseRude]

An update:
Today I tested spark plugs with in line tool and all 3 show spark with no firing from engine. Compression was checked (cold) and all three are 75psi. Starter spray was sprayed into spark plug holes, air intake, and carbs (separately) and engine would not fire at all. Fuel lines were inspected and no cracks/leaks found.

Given failure to fire with starter spray and spark, I lean towards low compression, but I would be surprised given how well the motor started and ran prior to these issues

 

[racerone]

Well compression should be about 120 PSI or so.----Investigate that first.----Does spark jump a gap of 3/8" or more on a test device ?----Does fitting for tell tale hose come off the side of the block or the top ?-----Has water pump impeller been replaced about every 5 years or so ?

 

[WildGooseRude]

Well compression should be about 120 PSI or so.----Investigate that first.----Does spark jump a gap of 3/8" or more on a test device ?----Does fitting for tell tale hose come off the side of the block or the top ?-----Has water pump impeller been replaced about every 5 years or so ?

Thanks for the reply, please see responses below:

• Agree that compression is low, but I was under the impression that engine would still fire above 60psi. It is confusing that motor will run roughly every other day tested - I would expect compression issues would be consistent
• Spark does jump that gap (tested at 7/16")
• Tell tale hose comes off the side of the block and spits out the back through a hole in the shell. Stream has been consistently strong throughout use when engine runs
• Impeller allegedly changed by prior owner 3 years ago, since then about 15 hours have been run. I am now questioning this. While the tell tale stream is strong, it would make sense that overheating would lead to issues causing low compression

 

[racerone]

A service bulletin came out in 1994 to move tell tale fitting from side of the block.-----A new location is on top of the block.----Latest water pump kit has all the details / instructions.----Before you spend another beer token , take the cylinder head of to inspect cylinder walls.