Mercruiser Diesel D-Tronic 4.2L 250 HP Help!!!!!

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Rbollat

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Anyone has recent knowledge or info on the Mercruiser Diesel D-Tronic 4.2L 250 HP? Every time I search for information on these engines on the Internet I get messages, forums, etc from 2007, 2008, etc.

Both my engines are having exactly the same problem, when you start them they accelerate by themselves all the way to WOT and then they stop. After this, they do not start for a couple of days and all of a sudden they start again and the same thing happens. We hooked the engines to a computer and the error message is that ALL sensors are "out of range". We have tested every electrical part of the engine with new parts (Computer, Electrical harness, sensors, instrumented injector, serviced injectors, serviced fuel pump, timing, etc.) and nothing works. Any idea what could be happening?

THE SAD STORY:

My boat is a 1998 Searay Sundancer 330 with 130 total hours on it!! when I bought it it had 104 hours. The boat really looks and worked like new when I got it, but the fantasy died when the engines started failing!!

The first engine died after using the boat 4 times and 17 hours!!! One cylinder head cracked and the piston connecting rod bent, so I performed a complete overhaul on the engine which took me 7 months to find the parts and $ 12,000.00 to complete.

Once the first engine was fixed, we took the boat out and used it 3 times and 9 hours and then the other engine died. But this time the mechanic said the problem was not that bad, it was just a cylinder head gasket and a defective injector. It took me 2 months to get the parts and I sent the other 5 injectors to get serviced. After spending another $ 6,500.00 to get this engine working, it never really did. So the mechanic started testing parts from the working engine on this one to see what was wrong and never found out what. After reassembling te first engine back with its original parts, NONE of them worked!!!

We found another boat with the same engines both in working order so we tested all parts of these engines in my engines and they did not work. It has been one year since the second engine died on me and I have no hope whatsoever to get my engines running again.

So, if help on how to fix the engines can not be obtained, I'm considering the option of installing new engines, but I really do not want to spend $ 45,000.00 + labor on two new diesels, so my question is, can I install 2 new gas engines instead? What size should they be? (5.7 L, 7.4L) Will my Bravo III X Diesel outdrives with 1.81 Ratio work with gas engines?

Thank you very much for any advice.
 
I hate to say it, but your mechanic is unqualified to work on these engines. He is shotgunning your problem rather than solving it. The fact that both engines are have the same problem, the fact that working parts from another did not work on either engine should tell you that the problem is not the engines but something feeding the engines, most likely electrical. Diesels cannot accelerate without a fuel schedule increase. Since the engines are electronically controlled, my guess is electrical feed. Let me ask you this. Has the boat ever sank or had severed water intrusion?
 
Exactly what GB said. The fuel supply is wide open and sounds like electronic safety systems are shutting them down. After all that work are you sure that the throttles were hooked up properly. Not backwards??
Find someone familiar wit those engines.
 
I'm sorry to say that both GB and Pdecat are absolutely right!! The bad thing is that I knew it from the start, that he did not have experience on those engines. My big problem is that my boat is located in Rio Dulce, Guatemala, Central America, where there are only 7 boats with this engines and only 3 reputable mechanics and none of them have experience on them!! There is only one Mercruiser dealer in the whole country and they have no idea either, they don't even have parts.

To my knowledge, the boat has never sank or had severe water intrusion, I think something like that would have been noticeable in any of the other components inside the bilge and everything is in pristine condition, even the engines, no rust whatsoever. But something that did get my attention is that the electrical wiring harness on both engines had severe corrosion problem and even some pins broken in the connectors. Since this part is no longer available from Mercruiser, we had to reconstruct the wiring harness. At first I thought that the reconstruction did not work so we tried the harness and connection box and computer from a third engine (Which is working fine) and that did not solve the problem.

The boat has been kept out of the water in a covered hangar all of its life. It took about 50 hours to drive it from Miami to Guatemala and the extra 54 hours that it had when I bought it were used in the span of 12 years that it had been here.

The electronic safety systems are certainly shutting it down, because when I hook up the computer the codes say that diesel pressure is high, engine temperature is high, every sensor is saying they the engine is out of range, but I did replace ALL of the sensors with working ones and the issue remains.

I did check the throttles and they are hooked up correctly.

Thanks
 
We will have to figure it out then. The rewiring is suspect if there is something that opens the throttles electrically to start.
Since both engines do the same and are four stroke, right? it is very unlikely to be burning lube oil. so the key will be to figure out what it opening the fuel rack. Some engine do start with the rack open. Is the throttle to fuel rack connection purely mechanical or does it go through some electrical box?

Do you have a wiring diagram??
 
boatdiesel is a good source for all things diesel
 
Ok, well your harness is most likely wrong. You might look at some "junk yards" for a new harness. You also might find out who manufactured this engine for Merc, i.e Cummins, VW etc as you might be able to source a harness from them. Alternatively you might look to see if you could get the boat to Panama to a qualified mechanic, there seems to be plenty there, or fly in a guy from Panama. Boatdiesel.com is a very good source as pdecat suggests.

Putting gas engines in is problematic because you need to change all equipment in the engine area to spark protected. If you are set to throw in the towel and change engines, I would look at a set of Yanmar diesels. They would couple up to your Bravos, although personally I would change to the Yanmar drives as well. Merc drives are crap, and I own one so I can speak from experience.
 
Photo's would help.
What is the basic 4.5 engine block used in? What truck?

Is your engine electronic?
Going to WOT at start up, until it senses an Error and shuts down is going to be in the Sensors/Computer.

If it's Mechanical injection, the throttle butterfly is being held open at start.
Sorry but I don't know what is making it quit after a time. I'm guessing the loss of +12 at the injector pump.

You have a mess there. Hope you can go take pictures of that other 'known good' engine to look for differences.
 
I agree it sound like a harness issues being the both motors are doing the same thing. I have a simply question is the harness cable shielded and if so did you connect the shield where you made the splice or did you just wrap it back on both sides and maybe tape it? I understand you tried another harness as a temporary test but if it was not fulling installed and maybe grounded this could very well display the same symptom. I'm very curious as to what it is and hope you both figure it out an report back to us for others to learn in the future.
 
My boat is 4 hours away from mu house, will go over the weekend and take pictures.

Thanks
 
Figure out if the throttles directly control the fuel rack or if the go to some electronics that actually control the fuel rack . If we could disconnect the electronic controls but still allow idle fuel and start engines normally we would begin to understand where the problem is. I suspect that there is a throttle sensor that is miswired. Removing every control and manually moving fuel rack would be a great start. To the best of my guessing all the sensors somehow connect to one point , fuel control. From that point it is probably a mechanically controlled engine.
 
I recall another small Cummins doing this -
a 3 liter I believe. Ran till it broke.
It's been a while but I think the diagnosis was motor oil leaking into the turbo charger then into the cylinders. No way to stop it.
 
Actually you can stop it by closing off the air intake. Diesels operating near oil equipment such as drilling rigs are required to have an air shutoff to kill them in the event of oil spray.
 
I worked on a Sub-Chaser (WWII) with twin Upright GM 16 Cyl diesels.

The Gaskets around the Blower's would fail and the blowers would suck engine oil in as fuel. The engines would run-away and the resultant explosion often sunk the Ship.

Next to the Air intakes was a big cage full of Pillows. The Oilers (black Gang) were to throw the pillows into the Intakes to stop the runaway engine.
 
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