95 Merc 5.0LX Carb adjustment procedure?

[Stinky_1]

Hello all. I will start first with a scenario then follow up with my questions.

My cousin purchased a boat a few weeks ago. Its a 94 Caravelle Legend 2100. the engine was replaced by a previous owner. The new replacement is a 95 Merc 5.0 LX (305). The person he bought it from had purchased the boat in the US, and brought it into Canada last summer. He never actually registered the boat in Canada though, and sold it to my cousin a few weeks ago. So I would assume it has been sitting in storage for the past year at least. The motor was supposedly rebuilt before it was installed, and it has about 100 hours on the boat since the installation. Now, the existence of this thread obviously indicates there may be something going on.

So, yesterday was the maiden voyage for the boat. the boat started fine, but then sputtered out and died almost instantly. We had to give it a fair amount of throttle to get it to start, and then to keep it running it was at about 1/2 throttle. after it warmed up we were able to put the throttle back down to let it idle. But within a matter of seconds it started sputtering and then would eventually die if we did not open it up again.

With the prop out of the water still we had TONS of black smoke coming out of the back and a VERY strong smell of unburnt fuel. It would seem obvious that there is either an over fueling problem, a lack of spark, or a lack of air.

We did take the boat out for a run anyway (stupid us!) and the boat would NOT go over 3000 rpm. We could coax it up to 3000 rpm, but when you opened it up past that you could feel the power fall off and the engine would start sputtering. If you didnt start opening and closing the throttle it would have actually died, but we could save it by going full closed and part open until the fuel would burn out and let it run again.

So, we went back to the dock, pulled the boat out of the water and now its sitting in my driveway.

So, We pulled the plugs, I was not surprised to see them completly BLACK!. BUT, the question now is......

Are they black BECAUSE the carb is dumping in too much fuel, so they got all carboned up?

Or

Are the plugs bad, and so the engine started running rich, and now the plugs are black?


We are getting some new plugs tomorrow and going to put those in, but I am pretty sure that there is going to need to be some adjustment done to the carb as well. The problem is I cant find really any information on adjusting the carb. What I did find was "adjust the carb". Which is great, if I knew where to look. I am not dumb when it comes to engines, but have NEVER been around a boat before. I also have not worked on ANYTHING with a carb since about 91 or 92, so its been a few years. If anyone has a manual scan that shows the procedure or can point me to a thread that talks about the steps it would be handy.

Also, when we do the plugs I wanted to verify the timing on it. May as well make sure everything else is good while we have the thing a part.
If anyone has any suggestions, or ideas based on what I posted above it would be appreciated.

Oh, I also noticed while we were running it in the driveway that the point that it starts to sputter out is where the little arm pushes down a shaft that squirts a spray of fuel into the carb. I imagine that is there on purpose, but because the engine is running so rich already that is what floods it out. I didnt want to start messing with anything until the plugs are done. Maybe that will cure the whole thing. But just in case it would be nice if I can already know where to go after that.

Thanks in advance.

 

[John_S]

Re: 95 Merc 5.0LX Carb adjustment procedure?

Make sure:

- Choke is opening fully
- Float needle not stuck and gas dribbling down the barrels at idle
- Nothing in the fuel pump check hose (if yes, need new fuel pump)

 

[Stinky_1]

Re: 95 Merc 5.0LX Carb adjustment procedure?

The choke seems to be opening just fine.

Where do I check the needles for gas dripping down the side?

I didnt look for anything in the fuel pump hoses, I would figure if there was a problem there I would have a shortage of fuel, which is clearly not the problem here. But there could be something with the needles, I just dont know how to check them or where to look. Is there a write up on that anywhere?

Pretend I am retarded when replying for checking carb specific things. I have almost zero experience with them. I am a Fuel injected kind of guy.

Thank you for the post.

 

[John_S]

Re: 95 Merc 5.0LX Carb adjustment procedure?

Mechanical marine fuel pumps have a safety check hose, such that when they fail, the gas gets dumped into the carb and not the bilge. When they start to go, causes a very rich condition.

You should have a Weber carb. Model? Look down the primary barrels while engine is idling (use flashlight). If you see dripping, and fuel build-up on top of the butterflys, you have an issue. Might as well do a complete carb rebuild/clean.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/17/17d5r2.pdf

 

[Bondo]

Re: 95 Merc 5.0LX Carb adjustment procedure?

Ayuh,.....

Get a Carb Rebuild Kit for that Carb,+ Rebuild it....

It needs More than just alittle Adjusting.......

 

[Stinky_1]

Re: 95 Merc 5.0LX Carb adjustment procedure?

SO this arrow shows a spot where I noticed a LARGE pool of gas. If you look in there while its running there is tons of gas in there. I thought it was a little odd that there would be any in there. Is that what you are talking about?

This arrow shows what I would guess is the adjusting screw to mess with the mixture. There is one on the other side as well. I would assume this is for each jet? Would messing with these be similar to a lawnmower? So you turn it all the way to the right, then open it 1/2 turn and adjust from there while its running?

And here is just another side shot of the carb. I was trying to get the writing on the side, but its hard to make out what it says

The side of the carb say "rochester" on it, and then below it says "quad barrel" or something to that effect. on the back it says "made in USA".

So, should it say webber on it somewhere if its a webber?

 

[John_S]

Re: 95 Merc 5.0LX Carb adjustment procedure?

Thats not a weber, its a Rochester Q-jet.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/17/17c5r2.pdf

Picture one, is the fuel bowl vent. Yes, you can see gas in the bowl.

Picture two, That is one of two idle mixture screws. See manual above for info on adjusting. Probably not causing the issue.

The yellowed hose by fuel inlet is the fuel pump safety check tube. If there is anything in it, you found all or most of the problem.

Did you look down the primaries after choke opens and watch what is happening?

All of engine manual: http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/17/17cov2r2.pdf

 

[Stinky_1]

Re: 95 Merc 5.0LX Carb adjustment procedure?

Thats not a weber, its a Rochester Q-jet.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/17/17c5r2.pdf

Picture one, is the fuel bowl vent. Yes, you can see gas in the bowl.

Picture two, That is one of two idle mixture screws. See manual above for info on adjusting. Probably not causing the issue.

The yellowed hose by fuel inlet is the fuel pump safety check tube. If there is anything in it, you found all or most of the problem.

Did you look down the primaries after choke opens and watch what is happening?

All of engine manual: http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/17/17cov2r2.pdf

awsome, thank you much for the link. I will be printing that off and go over all those settings tomorrow. It wont hurt to make sure everything is where it should be

Also I figured I better check out the fuel pump check hose thing. It could very well be a failing pump. SO, where should I be looking to find this check hose? I only recall seeing one hose coming from the fuel tank to the filter, and one hose from that to the side of the carb. unless I hear otherwise I am guessing I should see a spot where the hose would split, and one of the lines should be dry? When you say "nothing in the fuel pump check hose", I figure the "nothing" you speak of is fuel?

You guys have been a great help so far. Hopefully I can get through this and actually get the boat out this season to see what it can do.

 

[Stinky_1]

Re: 95 Merc 5.0LX Carb adjustment procedure?

SO, where should I be looking to find this check hose?

nevermind, I figured out where that hose was. In the second and third picture its the brown stained hose with the greenish tint to it where it plugs into the barbed fitting?

I pulled it off while it was not running, and there were no signs of anything in there. I also started it up and ran it for a couple minutes and pulled the line off, still nothing coming out. I couldnt let it run long because I still have one of the plugs out for comparison to find the new ones.

Needless to say, it did not run "much" worse with one plug out. So I am thinking that the new plugs will make a HUGE difference. And holding my breath that a quick carb look over will show that everything just needs a little "tweaking" to get it back right again.

One thing I was thinking, we are at 3600 ft, The boat came from Pennsylvania (I think) which could have been as low as 0 ft, but the average elevation is only 1000 ft. Would it have been setup to run richer at sea level, or leaner??

either way, I am grateful for the help so far guys.

 

[Stinky_1]

Re: 95 Merc 5.0LX Carb adjustment procedure?

ok, now I feel like a retard!

Imported J S told me exactly where the stupid fuel check line thing was. I just got so excited by the link for the carb that I must have missed ALL the rest of your post.

Either way, it has been detirmined that its not that now anyway, but I figured I better give credit where it was due.


Now, on to the engine manual link......... I had actually found that in the manual links thread. Has anyone actually opened that to look at it? the file is only 54kb, and from what I can tell its only 6 pages long. It seems there is a lot missing from it. Is anyone else aware of that? Or is there more to it that needs ot be downloaded from somewhere else too?

 

[John_S]

Re: 95 Merc 5.0LX Carb adjustment procedure?

Now, on to the engine manual link......... I had actually found that in the manual links thread. Has anyone actually opened that to look at it? the file is only 54kb, and from what I can tell its only 6 pages long. It seems there is a lot missing from it. Is anyone else aware of that? Or is there more to it that needs ot be downloaded from somewhere else too?

Go to the table of contents (last page), and sellect the section on the left that you want to hyperlink into. As you move the mouse pointer over a section, the pointer turns into a hand with pointing finger. I tested a few and they all worked.

 

[Stinky_1]

Re: 95 Merc 5.0LX Carb adjustment procedure?

I think you must have all the sections in the same folder as the cover page somehow already? The only one I was able to open was the section on the rochester carb because it was on the desktop as well. All the other ones poped up with an error that it could not find the file.

Is there a master download page where each section can be downloaded individually? Or is it supposed to be downloading the files needed as I click on the links in the TOC?

Note that I tried to use it in 3 different pdf readers and got the same results in all 3.

 

[Stinky_1]

Re: 95 Merc 5.0LX Carb adjustment procedure?

So, update time I guess.....


I finally got my friend to bring the boat back to have another go at it. I had a new carb I was borrowing from someone on a known good setup. So we were going to just swap it out.

I had been going through the forum the night before, and came across someone post where he had a VERY similar issue as mine. It turned out that he had set his timing and did not tighten down the bolt, so it slipped out of adjustment. I figured I better double check my timing again as well.

So, I found that the timing was set to 0. Which I always beleived it was supposed to be at 8?? So I changed it to 8 and instantly the engine started to rev up faster and faster (off idle). It was running a million times smoother.

So we locked down the dist, then I had to go back and set the base idle. So I got that turned WAY down.

After that I thought maybe I should double check that the pulley had not moved at all, which would have messed up my timing reading. We popped #1 cyl plug out and set it to TDC. Sure enough, the marks are off by a couple degrees. In the process I figured I should pull the primary coil wire off the dist just in case my friend decided to try and start the engine while I was setting everything. Once we were all done I went to plug the coil wire back in, but it would not snap on.

I took a look inside and found that the wire clip had been BENT over. So it could not fit over the post at all! I straightened that all out, and clipped it on. We tarted the boat up and it fired right up!. Idled glass smooth, NO MORE SMOKE out the tail pipe at all!!!

So, I messed with the carb idle adjustments a bit more, got them to where they seem really good. Re-set the base idle rpm and we are ready to go for a test run this afternoon.

So, it seems this whole thing was probably due to

Bad coil wire

And

Bad timing.


Thanks guys. I will post up if that did it for sure in a few hours.