95 omc cobra 5.0 wont plane, stalls at 4000

[bconley]

1995 omc cobra ford will not plane. If I ease into the throttle the bow will start to drop then the engine cuts out for .5 seconds then goes for .5 and back and forth. It almost feels like the governor on a car. Where it hits a certain speed then slows down a certain amount and will then allow you to accelerate again. It does it at 4000 rpm (dash tach) every time.

I have read about a limp mode (same thing but 2500) and coils and resistor wires not providing proper spark. I have replaced the fuel water separator and will test it tomorrow. That just doesn't seem like it will do the trick. The engine idles and runs smooth through the entire rpm range until 4000. Does it have a limiter? It is a four winns 200 horizon. The people I bought it from had their mechanic working on it. They replaced the battery cable, solenoid, and connections. They said their mechanic was stumped but said it had the be electrical/distributor related.

 

[Bondo]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Ayuh,.... Welcome Aboard,.... Sounds like it's runnin' outa fuel, from water in the fuel,...

Changin' the fuel filter just might Fix it,...

Inspect the contents of the ole take-off filter for water, 'n crud,...

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Well there was some water in there. A friend of a friend who is a "part-time boat mechanic" said it could be from being winterized and sitting for a couple months with just a quarter tank of gas, because condensation can build up in the tank during storage. Should I get this water evaporator and add it to the fuel tank? what is it called and how much should I add.

Let me apologize upfront. I don't know much about I/O's. I can work on older outboards and cars. This is my second boat and I am not familiar with winterizing/de-winterizing procedure.

Thanks for the quick response. As soon as the rain stops we will test it.

 

[bruceb58]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

If you suspect fuel contamination and its more than what just a fuel filter can do, run it off a portable tank and see if it does the same thing.

You have a carb or fuel injection?

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

It is EFI fairly similar to same year model ford mustang 5.0 from my understanding

 

[bruceb58]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

You are going to have a tough time finding people familiar with that system. Volvo/OMC is the only one that used it and only for a few years.

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

I agree. That's been the hardest thing so far. I have read that there is a resistor wire (purple and black) that goes from the coil to the alternator, which is there. This external resistance can increase with the age of the wire and cause a power loss or spark loss leading to a problem similar to mine. So would a weak spark cause the same problem. Now my question is, if it is electrical, as the marina mechanic stated, can I upgrade the coil to an internally resisted one and do away with this external wire?

 

[bruceb58]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

I would be surprised if they used resistance wires on an electronic ignition but who knows what Ford/OMC did! I do know they had a unique distributor on them.

You have an OEM service manual for this engine/drive?

You have your model number?

I am leaning towards fuel issue. Did your mechanic measure fuel pressures in his diagnostics?

 

[bruceb58]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

duplicate

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

My mechanic is replacing the impeller and fuel filter as we speak. He said he thought it was starving for fuel as well. The people who I bought from also had their mechanic look at and they said electrical/distributor so they replaced the solenoid, battery wires, and terminal connections.

It is confusing because it has no stutter or hesitation anywhere else in rpm range. At 4000 it falls on its face for a split second then picks back up and does that consistently until I throttle down.

 

[bruceb58]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Is your mechanic experienced with this engine FI and distributor system?

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Not exactly. He has built a few warlocks and other go fast boats which is his specialty. I do not have a service manual for this boat either. And the mechanics that are familiar with it are few and far between. Plus I do enjoy working on things but my experience has been cars, motorcycles, outboards, and small engines.

I am at work now and do not have access to the boat at this moment. I will call and see if I can get the model number.

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Heres an Update. Rotor button is corroded, plugs have gas on them. We will be testing soon. I guess or I am hoping a cap and rotor and plugs solves it. It could still be the coil producing a weak spark as well. I can not understand why the marina mechanic of the previous owner would not have checked such small maintenance style items. Thanks for the time. I will keep you posted so maybe others can gain something from what we discover.

 

[bruceb58]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

That would be good if that's it. I would have thought that would have been done already as well.

I would try to locate an OEM service manual if you can for the future. An OMC or Volvo one will be identical. Make sure its OEM. Did I say OEM enough times?

Make sure you look at the model number to get the correct one. It will have either "MD" or "HU" in it. OMC and Volvo have slightly different complete model numbers but they both contain those letters I mentioned.

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Yea I guess with my past experience and having heard "well my mechanic said........." I overlooked the obvious. For some reason I always expect the worst and forget K.I.S.S.

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Well we finally had some decent weather so I could test the boat. It still does the "stall". When I first take it out it will now hit 4500 before it sputters and gradually as the boat warms up it wont reach 4000 then as I continue cruising it wont hit 3500. I filled the tank with ethanol free gas and added water remover, new plugs, new cap and button. same problem it just I get 500 more rpms now at a cold pass than I did before.

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

oh and new impeller and new fuel filter. Also it is a 1995 5.0 MPI.

 

[bajaunderground]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Okay, your model, according to my OEM manual for a 1995 5.0EFI is...50FAPHUB* (220hp) (*as per bruceb58)
Spark Plugs: RS9YC (Volvo) or R42CLTS (Champion) Gap: 0.045 Needs to be checked
Ignition Timing: 5˚ BTDC @ 600rpms (idle) Needs to be checked
Idle Speed (in gear): 600rpms (not adjustable)
Max WOT (rpm): 4,200-4,600
Distributor Sensor Air Gap: N/A
Idle Mixture: N/A
Oil Pressure @ 2,000rpms : 40-60psi
Fuel Pressure @ idle: 31-39psi Needs to be checked
Compression Pressure (psi): 75% of highest Needs to be checked

The EFI system is similar to a Ford F150 5.0L from 1988-1995ish (I'm not 100% sure when started/finished) Most internals and computers (ECM) are all Ford. Finding a Ford specialist might be the way to go? You might be able to hook up to an OBD (SIDE NOTE: These requirements are generally referred to as "OBD-I", though this name is not applied until the introduction of OBD-II. The data link connector and its position are not standardized, nor is the data protocol.)?

 

[bconley]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

Spark plug gap is fine. Checked that when new ones went in. Idle fuel pressure is 44 psi. Idles at 1200 when cold then 1000 on dash tach. I will put a different tach on it tonight when I get home. I am also going to check voltage to coil and voltage from the alternator when I get home. Dash gauge is pinned at 16 volts. Coolant temp sensor never registers now that the impeller has been replaced.

 

[jerryjerry05]

Re: 95 omc cobra 5.0 wont plane, stalls at 4000

When it gets up to operating temp.
The coil might be breaking down.
Reach back and touch the coil and see if it's too hot to touch.
A normal operating coil you'd be able to keep your fingers on it.

The voltage to the coil? I think it's should be about 9 unless the coils has an internal resistor.