1989 Mercury 115 fuel/air issue

[Zmerc]

Morning folks,
Recently purchased a ‘90 Astro 16’ with an ‘89 Merc 115. 1st trip had some issues. At the launch, primed the bulb, bumped the key 2-3 times, fired right up and idled for 10 minutes with no problem. On take off it was a little sluggish/stuttered but not too bad. Ran about a mile up the lake, fished for 30 minutes, started right back up. Ran a mile back, fished for about an hour and it was impossible to get started back and keep running. It would fire almost every time but wouldn’t stay running. If I advanced the throttle, it wouldn’t do anything for a few seconds, then it would idle up quickly. It started better with choke and would run for a few more seconds but would still end up dying. Once I was able to keep it running long enough to move forward, it was not a smooth acceleration at all. Not quite bogging but almost like a gurgle if that makes sense. Does this sound familiar to anyone? My guess is a cracked fuel line or air getting in the system but this is my first 2 stroke so I’m unsure. Thanks in advance for the help!

 

[racerone]

Did you install a new water pump impeller.----That is always recommended on a used purchase.-----This motor only idles on the top 2 cylinders.---Bottom 2 carburetors kick in at about 1800 RPM.----Has oil injection system been checked ?----Post the compression numbers here.-----Does spark jump a gap of 3/8" on all leads ?----If motor sat for a long time with fuel in the carburetors they may need attention / cleaning.-----Checked for water in the fuel ?

 

[Zmerc]

Did you install a new water pump impeller.----That is always recommended on a used purchase.-----This motor only idles on the top 2 cylinders.---Bottom 2 carburetors kick in at about 1800 RPM.----Has oil injection system been checked ?----Post the compression numbers here.-----Does spark jump a gap of 3/8" on all leads ?----If motor sat for a long time with fuel in the carburetors they may need attention / cleaning.-----Checked for water in the fuel ?

Water pump, spark plugs, etc. were replaced earlier this year. It was a friend of mines boat, he replaced just about every small part you can replace the past year. New wiring harnesses etc. he always ran tank nearly dry before he stored it, I added non ethanol with a 50:1 ratio. When it was having trouble starting I could idle it up and once it got through the “bog” it would idle high just fine for about a minute then it would finally die. I forgot to mention I don’t believe it’s holding prime as it should. After 30 minutes I can get a full squeeze on the bulb. I replaced the fuel line from the hull fitting to the connector on the outboard (new hoses, bulb, and connector.) if it sits overnight trimmed up there’s a small spot of fuel that leaks out but I can’t figure out where it’s coming from. Also, oil injection system has been deleted, I just premix. Compression was checked this spring, I don’t remember numbers but they were good. I’ll check again this week

 

[racerone]

Fact-----The primer bulb does not stay hard when motor is running.-----And it does not need to be hard right after motor starts.----Bulb does nothing when motor is running.----You are pushing the key in and holding it in for cold starting ??----Does spark jump a gap of 3/8" on all leads , yes or no ?

 

[Zmerc]

Fact-----The primer bulb does not stay hard when motor is running.-----And it does not need to be hard right after motor starts.----Bulb does nothing when motor is running.----You are pushing the key in and holding it in for cold starting ??----Does spark jump a gap of 3/8" on all leads , yes or no ?

I mean bulb needs primed before every start not while running. Cold start starts great without choke. When it started having issues, without choke it would start every time I hit the key, but would die almost immediately. With choke, it would start great and run for 5-10 seconds and then die. Would start and run for 30 seconds or so with choke and throttle advanced slightly but would eventually die. When motor is cold it has no idling issues at all. Only issue when cold is when taking off it seems to lag or stutter some. I will check spark plug gap this afternoon

 

[Chris1956]

You might check the fuel pump diaphram. If they get a hole, raw fuel gets into the crankcase, flooding some cylinders and causing hesitation.

 

[racerone]

Normal for the bulb to be soft after motor has run.----This fact confuses many people.-----Sparkplugs have nothing to do with testing the ignition.-----Does spark jump a gap of 3/8" on each lead , yes or no ?---Do you push the key in and hold it iin while cranking it over ?-----When motor fires and stumbles you push key in momentarily as needed till motor warms a bit.