Engine stops when put in gear

[CaptainT]

My Yanmar 4BY-180 will start and you can raise the rpm in neutral,
but as soon as I put the shifter into either forward or reverse
the engine shuts down.
Is there some electrical interlock I’m not aware of?
The ECU was replaced because of a moisture issue and the boat
wouldn’t start. Now it starts but stops when put in gear.
Any help would be appreciated.

 

[Capt’nKarl]

I wish I could directly answer your issue but if there’s one thing I’ve learned over the years it’s if there’s a new problem look at the last repair done. Chances are something wasn’t connected right. This is what makes owning a boat kinda, maybe, considerably, somewhat, perhaps, maybe, fun.
CaptnKarl

 

[Toki]

I'm guessing you've already checked this, but ... are you absolutely sure the prop isn't fouled by a rope or some such thing?

 

[knotflying]

I agree, a fouled prop could be the culprit.

 

[CaptainT]

The boat is out of the water so I’ve inspected the prop and it spins by hand.

 

[BB marine]

First question is what does the fluid look like in the reverse gear? If it looks good and has no burnt odor or evidence of water or any other contaminants it's probably ok. The next question is does it seem to die because of extreme load something locking up or similar to you just shut it off? If it seems as something is locking up and the shaft turns freely I would look at the reverse gear even though all fluids look good. If it feels like it is just shutting down ( boat in the water) I would look for a fuel restriction. There possibly is enough fuel to start the engine but not enough fuel supply to run the engine under a load. A diesel runs by adding fuel. Check your fuel filters for restriction, (if clean )check your fuel pickup in the tank for restriction. As far as interlocks there may be one but I'm not aware of one an interlock for shifting in gear. There is a interlock or neutral safety switch for starting in gear but that is starter related and you can start the engine.

 

[CaptainT]

It sounds like I’m turning the boat off when it shuts off. It happens in both
forward and reverse. When I put the boat in the water at the ramp, I let
it idle for awhile and even revved the engine to at least 2200 rpm.
I put it in reverse and it died, started it again and it died.
Started it again and tried forward and it died.
Put it back on the trailer and took it out of the water.

 

[Brian B]

How about disconnecting the shift cable at the transmission. Start the engine and shift the transmission by hand with the lever the cable connects to and see what happens. If the engine continues to run it seems the problem would be between the new ECU and the throttle assembly at the helm. Sounds like something is amiss with the new ECU. You can do this on the trailer just have a hose going into the sea strainer.

 

[CaptainT]

Thanks, I’ll try that

 

[rackline]

Try the neutral safety switch. It's the the unit with wires attached where the shift cable connects to the shift lever on the tyranny. I'm not at the boat or I'd include a photo. As I recall there's a button that is the safety switch that rides along the shift lever or something in that area that can prevent the engine from starting when not in neutral. Maybe it's out of alignmnent or synch with where it should normally sit. Also, check the button/switch to make sure it depresses and releases as it should.

 

[bob daily]

I would try with what Brian said, I think your boat has a electrical controls, so by eliminating that and placing the shifter manually you will narrow your problem down to mechanical or electrical.
Just my two cents, good luck and hope your back up and running soon! Bob

 

[knotflying]

I might lean towards the neutral safety switch being out of alignment or defective. Try jumping it out and see what happens. Disconnecting the linkage won't determine if the switch is the problem so I would jump the switch first and if you still have the problem then do the linkage disconnect.

 

[BB marine]

I agree with disconnecting the shift cable and shifting in and out of gear. The reason I would do this is not to test the neutral safety switch it would be to test the control box. The throttle position sensor is located in the box. Leaving the control box in the neutral position ( engine running) shifting manual at transmission ( engine runs possible issue at control box) (engine dies keep troubleshooting) The neutral safety switch should not related to the fuel shut off after start up. The neutral safety switch is wired to the starter motor solenoid. If in gear or misaligned neutral safety switch the engine will not turn over because the neutral safety switch completes the circuit to the starter. There is a circuit that feeds to the shut off valve solenoid during the start up to apply higher amperage to help keep solenoid open. Once the engine is started this circuit is not needed. If the engine is running the neutral safety switch is out of the equation.

How long do you run the engine before shifting in Gear?
What is the idle rpm?
What is the engine operating temperature at when shifting in gear.
What is the max rpm in neutral that you can run up to?
Any smoke at idle?
Any running codes ?
How does the engine sound ?
Does it appear to be running on all 4 Cylinders?
Have you tried running the engine on a remote tank?
Salt water boat? Have you checked exhaust elbow for restriction?
Air filter clean ?
Fuel filters clean?
No evidence of fuel leaks or air leaks in fuel system?
fresh fuel ? old fuel?
What was running condition before ECU was replaced?

A diesel engine before common rail was simple ( air in without restriction) (clean fuel pumped at high pressure with no air in system to injectors rack driven, compression, and non restricted exhaust. These principles are all still used in the common rail but the are many electrical components doing what the basic components use to do. In troubleshooting start with the basics. Air in, fuel in, exhaust out. Next is each cylinder firing? If an engine is running and goes into gear and dies. (1) the reverse gear is locked up, or running gear is fouled (2) the engine doesn't have enough power to turn the prop. (3) fuel is being shut off by an electrical fault, not enough fuel, air in fuel, bad fuel, restricted air, exhaust, injectors,.....