Wiring question

I am in a 27 ft ocean master center console with a Steyr Diesel engine. My issue is that when we are running on a plane and hit a bigger wave and therefore a bigger bounce, the engine looses rpm for an instant and then goes back to the same rpm within a second. The mechanic says that he can’t think of an explanation from the engine side of it, but thinks that it may be a wiring issue under the console where there may be something coming loose when the bump happens. Thoughts? Also, how do I secure all that wiring? It is kind of hanging from the back side of the console...not fastened to anything.

Jack.

Welcome aboard. All wiring on a boat should be secured every 18”. That is the standard per ABYC. Go to Home Depot and buy a big bag of black zip ties. Get some that have holes in the end and some that don’t have holes. Then start securing the wiring. With the ties that have holes you can screw to something solid to secure the wiring. Good luck.

Does the engine truly loose rpm or does the gauge just flutter from the bounce. I can’t see how a wave bump would cause a Diesel engine to change rpms. You can’t trust your ears as sound waves are more affected by a wave bump than a Diesel engine would be.

The engine actually shuts off for a second....but comes back on by itself and is at the same rpm as before it hesitated....

That sounds like the fuel shut off solenoid is momentarily engaging. That could be caused by a loose wire or connection. Do you have a kill button or do you kill the engine bY turning off the key switch.

I am a marine electrician, not a diesel mechanic so this is a guess...could the prop be coming out of the water, starting to overspeed and the ECU shuts down the engine to save the engine from perceived destruction?

CharlieJ said:

I am a marine electrician, not a diesel mechanic so this is a guess...could the prop be coming out of the water, starting to overspeed and the ECU shuts down the engine to save the engine from perceived destruction?

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I agree with this.....providing it’s an electronically controlled engine. Sort of a rev limiter type thing.

How long does the engine stay off? Can you estimate a number of revolutions? Is it always the same, or is there a correleation to wave size (bigger wave means off longer)? When you say "off" do you mean no ignition (this is a diesel engine, right), or is there merely a loss of rpms?

It is off for about one second. The prop is not leaving the water. It is a mercury dual prop outdrive. I think it is a loose connection somewhere, trying to find it is the challenge.

Post #9: With this info, I agree, it is more than likely a poor connection in a harness connector (corrosion, loose pin, bad pin to conductor crimp, etc.). Physically shaking everything should duplicate the problem.

I was looking under the console and actually found a wire that was not well seated on the back side of the key switch. I think that might have been the issue. The wire was in place but not secure. I was able to push it back up to secure it....now just need to look for some waves to hit .....

Automotive crap wiring. Better get busy with a crimper and some ring terminals and replace all those spade-things and get some marine switches. Pretty silly that a cheap electrical connector can kill your boat. Exciting to be way out there, dead in the water because it's rough!

Might check to see if the builder bothered to use tinned wire too.

plynhky said:

I was looking under the console and actually found a wire that was not well seated on the back side of the key switch. I think that might have been the issue. The wire was in place but not secure. I was able to push it back up to secure it....now just need to look for some waves to hit .....

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If that wire was the RUN terminal that would do it. Consider recrimping the crimps with a good crimper.

Take Xsbank's suggestion into account also.

No matter what you find that is actually causing your problem and fix it, you should secure all the wiring so it isn’t moving all over the place. It should be secured every 18”. So fix the problem and then secure your wiring, it will pay off in the long run.