50 HP Mercury Fuel or Carb Problem

[MISC]

Hello all. My first post here. I just purchased a 20' pontoon with a 50 hp ELPTO Mercury on it and I am having some issues with getting it up to speed. First time I took the boat out I could only get about 2800 rpms out of it and it would stall at idle. I could barely get the thing back on the trailer. I am new to cleaning boat carbs but I took them off and cleaned them with some can carb cleaner and replaced the gaskets.I also went ahead and changed plugs and fuel filter on the engine. Put the carbs back on and took the boat out and it got up to 4000 rpms and would idle fine without cutting off. Seemed to have more power but still not enough. If I would push the choke in during running the rpms would jump up to around 4300 to 4500 rpms for a few seconds then go back to 3900 to 4000 rpms and stay pretty steady there. It just seems like I did not clean the carbs well enough so I have them off again and soaking in some B12 carb cleaner overnight. When I pulled the carbs off this time I noticed some black looking oily drops in the bottom of the bowls. Is this a sign of water in the gas or my old fuel lines dissolving? The boat had about 25 gallons of fuel in it when I bought it and I have no idea how old it was or what quality it was. I added about 10 gallons of non ethanol and a can of Sea Foam to top it off before I ran it the first time. If I have some bad fuel then I will get it out. Going to buy a water separator for it tomorrow. Just wanted your all's opinion on what you think I have going on. Hate to dump 35 gallons of gas but if that is the problem then I will get rid of it. I am attaching a picture of the bowl from today's carb teardown. Keep in mind they were cleaned the day before. I kind of smeared one of the spots(in the lower right) trying to see what it was but you can see the other black spot in the middle. The brownish stuff on the left is from the first cleanout and that stuff is like varnish. Very hard to get it all off. Thanks in advance for your responses.

 

[enginepower]

I have seen that before on a motorcycle carb. Somebody put some liquid tank liner and didn't let it cure completely. It was pretty tough to remove from carbs but I doubt this is your case. I would replace the fuel lines regardless since this is a new to you boat. Inspect inside of tank if you possibly can.

 

[frustratedboater]

Fuel: I have have similar issues in the past with other boats and have to trace back from supply to carb to rule out. I have recently changed all my lines from the fuel tank, to the separator, and to the engine. "I sleep well at night".... I have also tilted the tongue of the trailer to settle any junk in my fuel tank to the back corners, and siphoned a lot of water and debris out and was very surprised how much came out.

On a similar note, have you checked In-line filters and fuel/water separators? This appears like you had some, debris, or some gasket/hose deterioration (like you've said) contributing to "particles" in your fuel getting sucked up and clogged into the high-speed, and or low-speed fuel circuit. I hate to say this, but you may need to pull the carbs and blow out the high-speed jets. It appears that there may still be something in one of the carbs clogged up again. Pull everything off, needles, all gaskets, and blow it all out with compressed air and be sure you have good air flow into each jet-opening and good exiting air coming out!. Take special note when you pull them again. Keep them level and see if you see any more junk in them. If you do, it is coming from your lines, or tank...

Keep us posted...

 

[frustratedboater]

I forgot to mention, try a little acetone in the bottom of that carb 'pictured' and see if that will cut that sticky stuff and take the varnish off (if you haven't already). It looks a lot like that OMC gasket sealer.

 

[MISC]

Hey guys thanks for the responses. The B12 soak worked great and the engine ran like a champ today after I put them back on. I guess I did not get them as clean the first time. I also added a water separator filter for good measure but if i can help it there will never be another drop of ethanol fuel go into my boat as long as I have it. There is a station on the way to both ramps I use that sells non ethanol fuel and that will be a regular stop for me whenever I head out. I think my tach might be a little off though. It was reading 5500 rpm and I still had a good bit of throttle left. I don't think that engine was turning 5500 like the tach reads. Will have to get that checked out but just really relieved the engine is running well now.

 

[enginepower]

Glad you got it running good. I hear you on the ethanol. The older engines were not made for that. It requires special fuel lines and you would have to increase your jet sizes to richen it so you don't over heat plus you would lose some power. If tach is reading right and you still had a good bit of throttle left, you may be able to installed larger pitched prop which will give you a little more speed but depending on how much load you plan on putting in it, you may want to keep it where it's at and not run full throttle when not loaded.