GT-40 Issues. Urgent!

[Rock_Toy]

1996 SSN with GT-40 Pro Boss. 885 Hours. Runs fine when we put her in the water. Great idle, acceleration, etc. Boat runs at 120-140 degrees tops, probably due to the way the heater is plumbed. Blocking off the heater hoses tonight to try to fix that. However, after an hour or two on the water, the motor starts missing hard at idle and then dies under acceleration. Then won't start back up. Today, we had her parked on the beach for about two hours listening to tunes, then fired her up and the same thing. Barely made it back to the ramp. Kept dying and barely firing up. Backfiring like a mofo as well. Just had a full tune up. Timing is one, plugs are good, etc. Anyone have an idea? I think that the injectors might be malfunctioning. Never been replaced or serviced. Also smells "gassy" when running.

Would love our feedback. Also, which injectors would I need and how much are they?

[DanielC]

RE: GT-40 Issues. Urgent!

Do this:
http://www.planetnautique.com/index....=fuel+pressure
Report back.

[Rock_Toy]

Don't think that would cause missing and backfiring, do you?

[Rock_Toy]

Also, when we get her started and put her in gear, she surges pretty hard and will not get up to speed. Feels like a fuel issue but I seriously don't think its the fuel pumps. I just replaced the high pressure pump less than a year ago....

[DavidF]

Ignition coil. All symptoms seem to be indicators.

[bchesley]

I am thinking this is mostly a ignition issue. Although I highly doubt a coil on a GT-40 motor has gone bad it could happen. They are TFI ford coils and are pretty bullet proof. There is a reason that Skidim does not stock them as they just dont go bad. Any coil from a ford f-250 with a v8 from 88 to about 95 will work in a pinch. I would be looking at the distributor more closely. The module on the inside can go bad and cause this type of issue. Not sure where you will find one to salvage your memorial day though. Check all connections on the ignition side to see if you might be grounding out some where?

[DanielC]

Unless you have a marine engine with a catalytic converter on it, there is no feedback to the engines computer on the fuel air ratio. The computer just assumes the fuel pressure is correct. If you do not know that the fuel pressure is correct, it is pointless to try to diagnose driveability problems.
Here is an ignition system test I do:
http://www.planetnautique.com/index....=gt40+ignition
The spark tester is a lot cheaper than a fuel pressure gauge setup, so it is definitely a good idea to check that.
Like I said in the ignition post, this only checks the primary ignition system, and the secondary system up to the wire that goes into the distributer cap from the coil. The distributer cap and rotor, spark plug wires, and the spark plugs could still be bad.
You say the boat just had a full "tune up". What do you mean by that? There is really nothing to adjust or change that would be normally be considered "tune up"

[Rock_Toy]

Nuther development. Just pulled the "cover" off the top of the motor and discovered that the spark arrestor is completely gummed up. I quite honestly can't believe that the boat even runs!!! Do you guys think this can be attributed to the backfiring, poor running, etc? I would think that it would just ALWAYS run poorly.....as opposed to what is happening now, which is that it runs well for about an hour and then goes kaput.

[bchesley]

It might contribute but I highly doubt that this is the culprit. Clean it and run it. Unfortunately this type of symptom is gonna take some parts swapping to find.

[nms1991]

Take out your thermostat and check for debris in the shutter area for the low temp problem. But to trouble shoot the fuel system you need a fuel pressure gauge.

[AirTool]

Unless you have a marine engine with a catalytic converter on it, there is no feedback to the engines computer on the fuel air ratio.

I think you meant an oxygen sensor.

I did have an 82 GMC 2.8 that had O2 sensors and cayalytic converter but I don' t think the data was used to control the fuel mixture directly...perhaps it was used to control EGR and timing? I think cars from 76 to 81 may have had catalytic convertors w/o O2 sensors. I'm thinking the O2 sensors came out with the government mandated OBD1.

[Rock_Toy]

I am running out of options here. Have changed the plugs as well just iin case and still the same issue. Fires up just fine and runs like a champ for a while, then deteriorates. Start surging, running rough, backfiring and eventually dies. Then hard to start up and runs like crap until you can't start it all.....

[Teleman]

Fuel?

[Rock_Toy]

Thta's kind of what I am starting to think. How would I go about replacing all of the fuel in the tank, lines, etc?

[Zigzag55k]

Ok, slow down. First get yourself a five gallon gas can and rig up some fuel line from the can to the motor. Try this and see what happens. start at the closest point to the motor and start working your way back until you are back by the tank with your auxilary tank. You want to eliminate all variables. My guess is the whole fuel delivery system needs to be cleaned after looking at that flame arrester. Hope this helps.

Mark Q