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...

NAHIM · #7 07-08-2005, 07:12 PM

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,

CaptScottNC · #8 07-08-2005, 07:16 PM

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?

Bigshrimpin · #9 07-09-2005, 02:36 AM

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?

peterb · #10 07-09-2005, 04:40 PM

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

There are some knowledgable and friendly people on this site.