Mercury 90 running super rough, fuel coming out from throats of carbs.

[Kurt Watson 72]

Need more help. I posted my problem a few weeks ago, but still need more info. I bought this boat with a 1983 Mercury 90 2 stroke. Took it out 2 times. First time it ran great. Second time, after about 20 minutes of running, all of a sudden, it started running really rough and popping. I thought I had run out of fuel, but still had a 1/2 tank. It idles well, but wouldn't accept hardly any throttle input. Also had a lot of blue smoke, like it was running super rich. From what I've been reading, it sound like my problem could be a cracked exhaust splitter? It bothers me that fuel was coming out of the throats of all 3 carbs, like the exhaust has a blockage. I plan on taking the boat in to a local boat mechanic and want to give him all the info I can. Also, if it's going to be an expensive repair, I don't want to bother yet since I don't have a lot of money and would have to save for the repair. Yes, It has fresh fuel with 2 stroke oil, and water is peeing out the tell tale, so I don't think it was overheated. I can see ignition components were replaced in 2017 and then it sat for 3 years, but did have fuel stabilizer in it and the fuel I drained from it did not smell bad.

 

[Scott Danforth]

How long did the boat sit before you bought it? Have you gone thru the carbs

 

[ThomW]

If it sat for 3 years...even with stabilizer in it...that means the carbs had gas sitting in them for 3 years. Like Scott said, I would start with carbs. pull them and thoroughly clean them. Could have started running fine until a spec of something found its way into a jet and clogged it.

 

[Kurt Watson 72]

How long did the boat sit before you bought it? Have you gone thru the carbs

3 years. He did have fuel stabilizer in it. I don't know if he ran it after putting in the fuel stabilizer to get it into the carbs or not. It just seems strange that it was running perfect and then in one second started running so bad. The fuel dripping out of all 3 carbs is worrisome when it idles fine.

 

[ThomW]

3 years. He did have fuel stabilizer in it. I don't know if he ran it after putting in the fuel stabilizer to get it into the carbs or not. It just seems strange that it was running perfect and then in one second started running so bad. The fuel dripping out of all 3 carbs is worrisome when it idles fine.

Fuel dripping out of carbs is a sign that the float needles aren't doing their job and are gummed up and stuck. Start with the carbs....

 

[airshot]

Do a complete rebuild with rebuild kit for each carb. Just taking them apart usually doesnt work well and they will end up needing rebuilt anyway

 

[jimmbo]

It won't be inexpensive, just getting the carbs off, is a pain. Factor in the time to disassemble, clean, reassemble, reinstall, and doing the Link and Sync, adds up in time, and therefore Dollars. Hopefully the guy you're taking it has the proper info for setting the carbs and the L&S

 

[Kurt Watson 72]

Fuel dripping out of carbs is a sign that the float needles aren't doing their job and are gummed up and stuck. Start with the carbs....

But wouldn't it not idle at all if it was stuck floats? That's what has me stumped - my engine idles well. Only acts up with throttle input. I'm pretty good with vintage auto engines, but I'm completely inexperienced with outboard motors,

 

[Scott Danforth]

It will still idle with stuck floats, just spitting fuel all over

 

[jimmbo]

My 84 115 didn't like idling when the Floats got stuck

 

[Kurt Watson 72]

Well, I took it to my local mechanic. He works out of his house. Had to drive about 1/4 mile on a washboard dirt road (in the country) When we fired it up, it ran OK, so the washboard must have jostled something. I'll be running it on the lake this Monday, maybe this weekend to give it a try under load. Maybe the seafoam helped after it was in the carbs for a week!

 

[jimmbo]

Those Floats have been known to Wedge themselves a bit crooked and refuse to rise up and close the Inlet. At least that was what the ones in my 115 did a few times. I got pretty good at taking the Inlet-cover off the carb, and/or gently tap the fuel bowl with a Rubberized Hammer.

 

[Kurt Watson 72]

Thanks. I'll try that if it acts up again.