Engine Trouble... anyone got any ideas??
 

Engine troubles of course on the maiden voyage. Let me give you some background and you can tell me what you think if you don't mind.

1995 Mercury 3.0L Black Max 225hp with brand new powerhead and lower unit. Boat was test drove in Florida about in April and then I've had a hard time getting it up here. Compression is perfect and the boat ran 46mph on the sea trial done by the surveyor. No problems.

I took it out for the first trip and we idled out... boat did fine.. smooth idle. Got out of the No Wake Zone and smoothly pushed the throttled down. She started to come out of the hole and on plane and at about 15 mph she completely lost power but did not quite shut off. This was about 2 to 4 seconds after putting the throttle down. It coughed a little and I backed the throttle off and then she went right back to idling smooth. I tried it again and it lost power much quicker this time never trying to get out of the hole. The bulb felt flat and my first thought was a fuel restriction of some kind. If I pumped the bulb up hard it would try to get out of the hole and die back. Well it ran just fine at 1200 rpms but if I eased up over that much it would lose power and almost shut down. Sometimes it did shut down. Ok.. now we decided to just troll for blues about 5mph or 1100 rpms. Boat did fine but if we rocked hard by a boat wake it would cough and sputter and die or possibly not die and get back to idling once the wakes passed. It seemed to need to rock pretty good to make this happen. Normal boat wakes didn't do it but a big sport fish or good swell would cause the engine to struggle and cough even at 1000rpms. So now I'm wondering could it have something to do with floats in the carbs or fuel sloshing around in the gas tank or what? It does it very soon after the boat rocks hard.

Ok.. put it on the trailer I looked at the water sep filter and it was rusted onto the aluminum housing and the housing was completely corroded. No hope of even saving the frame of the sep filter. I bought a new Racor filter and frame and installed it along with a new section of line from the filter to the engine. New bulb and all. Bulb pumps firm very easily. Thought a check valve could be messed up in the bulb and it was a bit old. Ok... took the boat out today. Idled around fine and the boat even ran fine out of gear on a hose up to 5000 rpms. Idled around smoothly about 1200-1300 rpms casting at spanish then decided to head out to the inlet. She came up on plane almost probably reaching almost 20mph and I thought it was fixed then it suddenly died again. Then the same exact problems. Only thing that was different was that it started idling much rougher after that and then might idle smooth for a while. Rough for the next 20 minutes and then smooth for a minute or two but if you pushed the throttle much you got no response and it would lose power or shut off.

The tank is half full and sat half full often I would imagine down there in florida. Could it be water in the fuel tank?? Do I have a water sep filter in this model engine as well? Honestly I have to look agaain to see. The sloshing is making me wonder floats, carbs, water? The boat sat too long with some bad fuel and then something about trailering it 12 hours sloshing around a half empty tank?? any ideas???

Re: Engine Trouble... anyone got any ideas??
 

Did you drain the bowls on the carbs? they could be half full of water with the fuel floating on top, when you put the throttle down some other jets may open letting the water in...someone more familar with carbs can provide input. After draining the carb bowls I would hook up a six gallon portable tank with fresh gas/oil (assuming you have to premix) and test the motor, you can then determine if the fuel supply is the issue.

JW

Re: Engine Trouble... anyone got any ideas??
 

I agree, sure sounds like a fuel problem. Either you have some sediment in the fuel system from the rusted filter and/or water in the fuel. Do the test JW-Tex mantions and then drain the tank, lines and as much of the fuel system as you can, flush the system, refill with fresh fuel and test it again.

Re: Engine Trouble... anyone got any ideas??
 

Please follow up with the results of your efforts.

Re: Engine Trouble... anyone got any ideas??
 

tried an experiment... I had a guy pump the bulb while trying to geton plane to keep it solid. Didn't really help. Still had the problem. Does this help any?

Re: Engine Trouble... anyone got any ideas??
 

replace all filters and have your gas tank pumped/cleaned. my friend just went through this with his new 23...

Re: Engine Trouble... anyone got any ideas??
 

Just pulled the carbs and dumped some of the gas... pumped some gas directly into a cup by squeezing the bulb. small flecks of garbage in each pump. Looks like about 3 or 4 flecks about the size of very small grains of sand. That's enough to cause some trouble I'd say... everyone agree? I'm getting a portable tank and going to see how it runs on that after I clean out the carbs and replace the inline filter. Hope this helps some. Just not sure why it runs just fine without any load up to 5000. Guess it's not pulling quite as much fuel.

Re: Engine Trouble... anyone got any ideas??
 

after cleaning the carbs dont forget to break the fuel pump down because it will have trash in it as well. that would be a good time to put a kit in it too. and replace the small inline filter in front of the pump. Les

Re: Engine Trouble... anyone got any ideas??
 

the trash in the gas is the key - that may have come from the bum fuel filter you already replaced, or it may have come from the tank, and gone by the bum fuel filter -

either way, having replaced the fuel filter, Everything upstream, from the filter, thru the pumps, into the carbs, needs to be cleaned out now. That should get the engine running smoothly again...

But you still need to find out what caused it - mostlikely need to clean and purge the tank, and the lines.

As to the engine pulling 5000 rpm no load - not surprising - I've run motorcycle for many years, they are much the same, engine wise, with no load, you can hit red line with just a quarter throttle, but it won't take any load like that without bogging right down.

Anyways - it's critical to get the gas system cleaned out all the way - if a piece of residual dirt, downstream of that new fuel filter, gets into the carb, and partially blocks the main jet, your engine will start running lean, and then trash the powerhead in short order - bad carburation is the fastest trip to a seized engine.

Bill

Re: Engine Trouble... anyone got any ideas??
 

OK.. here is my update. Soaked carbs for a couple hours in GUNK carb dip with all the plastic removed. Went and bought the rebuild kits and reassembled them after cleaning. They were a little dirty but not as bad as I thought. Pretty simple carbs too. Well, put it back together and new inline filter and then added a portable fuel tank to the line to rule out the intake and keep any garbage out. Well..... went to the ramp tonight and put the boat in the water but still on the trailer.

Cranked her up and she sounded pretty good. Let her idle a bit and then put her in gear up to about 2500 rpms really churning some water. Sounded good. About 45 seconds later she sputtered... dropped all power and really coughed. I thought she might be getting out a little trash even though there should be none now. Tried again and did the same thing. Then the period of runnin smooth dropped down to only seconds at 1500 to 2500 rpms before she'd lose power or shut off. THen I tried at idle in the water. Ran up to 3000 rpm's and let it sit at that speed out of gear. After a little while it started missing a bit and running rough. Then I simulated the boat wakes we hit the other day that caused the engine to die even at low RPM's. I grabbed the T-top post and shook myself back and forth shaking the boat pretty decent while still on the trailer. The engine tried to die immediately even at low rpms while shaking the boat but when I stopped shaking it would start idling pretty smooth again in a second or two.

Any chance I have some loose connection?? The skeg on this boat took a decent knock chipping it in a minor traffic accident a between the last time it was run on the water and now. Don't know if I could have a loose wire from that or what? The trash still was going to be a problem although it wasn't the smoking gun in this case.

On the bright side some people got a good laugh watching me shaking my boat in the dark on a public ramp up here!

I have some photos to attach that I had some questions about. http://img.photobucket.com/albums/v6...boardcarbs.jpg

Look here and see the spot a hose looks like it should be. Assuming it should not have one since the engine ran fine when surveyed but I haven't been able to get it on the ocean for a run myself. In case you can't tell this is the starboard side by the carbs. Those 3 hoses come out and connect to the top of the carbs. There is another hose coming in the side of that little pump. This naked hose barb is coming straight out from the back.

http://img.photobucket.com/albums/v6...rbsoilline.jpg

This photo shows the oil reservoir and the port side of the carbs. Notice where the hose to fill the oil reservoir would normally be clamped in place. Now on the bottom of this there is an elbow with another hose barb pointing straight down. Is there supposed to be something attached here as well or is this some type of vent to let air in as the oil level dropped and prevent a vacuum? I noticed a little drop of oil hanging there at times.

Thanks for all the help. Tomorrow I'm going to try wiggling wires and pulling plug wires to see if I can narrow down what cylinders are giving me trouble and what the deal is. A mechanic at the dock thought it sounded like it was missing a couple cylinders. Asked about coils. WHo knows.

Re: Engine Trouble... anyone got any ideas??
 

i thought mine was a fuel problem,my black max would start skipping ,sputtering wouldnt idle. went through everything your doing, than i went through the electrical. Replaced the stator, crank trigger, finally i replaced both cd boxes( they have to be replaced as a set) and that cured the problem. Les

Re: Engine Trouble... anyone got any ideas??
 

CD boxes? Go by another name? not that familiar with Mercs or outboards in general but I'm sure learning a lot day to day. The shaking of the boat making the engine die is what's really bothering me.

Re: Engine Trouble... anyone got any ideas??
 

Hate to say it but it is starting to sound more and more electrical. check your grounds especialy the grounding areas where the cd boxes ground to the block. A weak set of batteries or jump starting a merc will screw up a cd box faster than anything. The merc shop manual says fuel systems are the most often blamed but least likely to fix the problem. Les

Re: Engine Trouble... anyone got any ideas??
 

What exactly are the CD boxes? and What is the best way to rule out the CD boxes and trouble shoot those? I don't yet have my manual for working on this engine to take me through the trouble shooting steps. Going to try and find one today.

Thanks everyone.

Re: Engine Trouble... anyone got any ideas??
 

OK... Have a little more information. All cylinder are sparking although some appear to be sparking "weakly" and not near as strong as the others. All of this is at idle on the hose. I put a screwdriver in the plug wires and checked for the arc to the engine block or spark plug top. I will try and show a text diagram of the results unplugging each wire had on the engine idling. I unplugged each one at a time and recorded the change. This is from top to bottom if you were looking at the back of the engine.

Port Cylinders

Moderate change

No change or
maybe very little

BIG change

Starboard Cylinders

No Change

BIG change

Moderate change


Ok.. now what do you make out of this? Also, All plug wires zap me if I unplug them at idle by hand even through the insulation except for the middle port cylinder and the top starboard cylinder wires.

Electrical problems are so much fun. I hope to fix this today if I can figure out where to go next.

Re: Engine Trouble... anyone got any ideas??
 

OK..another update. Just switched CDM from the number 1 cylinder that was so weak and had no change when pulling the wire and swapped it with the CDM from the number 3 cylinder just below it. The spark was stronger on the #1 cylinder but it still had no change when I pulled the wire on the engine idling. The spark was not as strong from the CDM I put on #3 but still had a significant impact when I pulled the wire and it ran rough. Is it possibly the #3 cylinder is just more "vital" for idling then the #1 and I still could have a faulty CDM??

I did not switch the CDM from #4 and #6 yet but I suspect I will have the same results. What is upstream from the CDM that I have to check?? and how do I troubleshoot that? or is it still possibly a CDM problem?

Re: Engine Trouble... anyone got any ideas??
 

the cd boxes are on the starboard side, they are stacked together one on top of the other, lots of wires going to them . some merc dealers say they have a tester to check them but most just replace both boxes then test the motor in the water.This is usually the first thing they do because they are 90% of the electrical problems on a merc. also look at the stator, it is located under the flywheel, you can see the bottem of it between the flywheel and the block , look for any spots that have got hot , the paint burnt off, or black tar hanging down. the stator is your charging circuit, low and high speed windings. most of the wiring along with the crank trigger wiring and other block sensers goes to the cd boxes wich control the firing of the coils. Remember if you replace a cd box you need to replace both as a set because a new one will usually burn out the older one. There is also the chance of a damaged flywheel or crank trigger that might of gotten damaged during impact. Les

Re: Engine Trouble... anyone got any ideas??
 

"CD boxes? Go by another name?"

I've always heard these refered to as "switch boxes"

Re: Engine Trouble... anyone got any ideas??
 

Bigshrimpin,your right, switchboxes in a CDI system. Les

Re: Engine Trouble... anyone got any ideas??
 

Capt Scott heres 2 great web sites with troubleshooting help outboardparts.com has the best prices and quick shipping and maxrules.com has the best troubleshooting info. Les

Re: Engine Trouble... anyone got any ideas??
 

Capt Scott,

I had the same problem and it drove me crazy. I will assure you that it's you're fuel vent. Replace the old vent and give her a try. It's air not getting in the tank that creates a vacuum. Tell me how you did.

Tight Lines,

Re: Engine Trouble... anyone got any ideas??
 

Wish it was that simple since it had the same exact problem when running on a portable tank I know this particular problem is not due to the vent. But it would be very likely if these problems went away when using the portable tank. Thanks for the input. Anyone else have any guesses?

Re: Engine Trouble... anyone got any ideas??
 

CaptScott - You might try mining these sites.

http://www.boatsetup.com

http://forums.screamandfly.com

http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi

The "boat shaking fix" makes me think you might have a faulty check valve on your main fuel tank. You might have more than one problem.

When you run on a portable tank are you using the same fuel line/bulb?

Re: Engine Trouble... anyone got any ideas??
 

I have have great luck with http://www.iboats.com.

There are some knowledgable and friendly people on this site.