Engine Trouble... anyone got any ideas??

CaptScottNC · #1 07-06-2005, 12:05 AM

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???

JW-Tex · #2 07-06-2005, 01:23 AM

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

nestorpr · #3 07-06-2005, 02:19 AM

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.

ocuyler · #4 07-06-2005, 02:59 AM

Please follow up with the results of your efforts.

CaptScottNC · #5 07-06-2005, 10:17 AM

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?

Abe's Rocket · #6 07-06-2005, 10:43 AM

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

CaptScottNC · #7 07-06-2005, 12:28 PM

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.

salvagefirst · #8 07-06-2005, 02:00 PM

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

oldbluesplayer · #9 07-06-2005, 04:10 PM

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

CaptScottNC · #10 07-07-2005, 12:48 AM

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.

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.

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.