4.3 TKS Shutting Down After Warmup

[Kdubsc]

Finished the carb rebuild. New plugs and wires. Cleaned cap for now until I can get a new OEM cap. Ran on muffs and seems to run a little better, but it was never noticably bad before. Only when she shuts off out on the lake at 3500. Next trip on the lake will tell the story. I'm hoping it fixed things for now. Perhaps the cap was crudded up enough to make it hard to provide good spark on the older plugs. Maybe it was something off in the carb. Who knows.

 

[alldodge]

Hope your good to go

 

[Kdubsc]

Hope your good to go

Unfortunately all is not well. Ran on muff today and had the same issue I've had all along. Once she shut down at idle. Another time after getting her easily restarted, I hit the trim button and she died. Now she won't start up at all. Turns over like a champ, but won't run. I took the flame arrestor off and gas is still firing into the intake if I pump the throttle. Not a venting issue as removing the fuel cap did nothing.

At the point, should I doubt the distributor cap and ignition coil? Seems electrical and I've cleaned every thing I can access.

 

[alldodge]

hit the trim button and she died.

That is a bad connection
Could be the 10 pin engine connector

 

[Kdubsc]

That is a bad connection
Could be the 10 pin engine connector

I've pulled that several times and inspected. No corrosion and no bent pins. One thing I did just do was shock the heck out of myself checking wires with engine running (finally). I let it sit for a while and checked the distributor cap again (new Quicksilver on order) and it fired back up. As I was probing around I made the mistake of letting the meter probe touch the outer jacket/boot of the ignition coil lead. A quick zap ensued (of me). Is that normal or is the wire and/or boot bad? Touched it again with insulated pliers and got spark as well. Right through the boot. Maybe I'm just an idiot, but it was sure exciting for a minute.

 

[Kdubsc]

Also tried replicating trim issue and it didn't happen. So its very intermittent and acts up when it feels inclined to do so.

 

[alldodge]

If the trim kills the motor, there is a bad connection somewhere, or the motor is shorting out. If its shorting out then it wouldn't move much at all

If your getting shocked by plug wires then they are leaking and need replaced

 

[Kdubsc]

If the trim kills the motor, there is a bad connection somewhere, or the motor is shorting out. If its shorting out then it wouldn't move much at all

If your getting shocked by plug wires then they are leaking and need replaced

The trim motor moves the drive up and down without issue. I've cleaned and released connections at the battery and everywhere else I can reach. Very confused.

Going to return the wires I got (Sierra) and get Quicksilver from dealer. Any chance those play a role in weakening the system to a point the trim draws enough to kill it? If not, back to standing on my head looking at connections.

 

[alldodge]

Don't see the wires causing the motor to die unless they arc over the the control module or other side of the coil (negative side) that kills the motor

 

[Kdubsc]

I guess the mystery continues. Will see what the new cap and wires do this weekend. Not optimistic.

What I don't understand is the same issue occurs multiple times the first 30 minutes out on open water. After stopping for lunch or to swim, it runs like a clock the rest of the day. Seems odd that a loose connection would fix itself that way every time. I sure wish I had a simpler issue to decipher.

 

[Kdubsc]

The trim motor moves the drive up and down without issue. I've cleaned and released connections at the battery and everywhere else I can reach. Very confused.

Going to return the wires I got (Sierra) and get Quicksilver from dealer. Any chance those play a role in weakening the system to a point the trim draws enough to kill it? If not, back to standing on my head looking at connections.

Meant to type "recleaned" and not released.

 

[Kdubsc]

Ran her again. Didn't change anything, but she idled and accelerated without issue. Anyways, did notice that the blower speed dropped noticeably with something as low powered as flipping the nav lights on. Just seemed odd, as the battery tests out and the voltage from the alternator is 14+.

 

[alldodge]

did notice that the blower speed dropped noticeably with something as low powered as flipping the nav lights on.

There is a bad connection somewhere

 

[Kdubsc]

There is a bad connection somewhere

I've polished battery connections, checked the ground connections at the back of the engine, checked ignition switch for loose wires, etc. I do still have wingnuts at the batterh, although they're tightened by pliers. A lot more to check im sure, but I'm close to giving up the driveway mechanic work.

Only electrical change before this started was a shop replacing trim sender and limit components. Not sure if they could pinch and short, but I've checked what I can see and don't notice anything abnormal.

 

[Kdubsc]

In trying to get the boat running for the weekend I located a cap and rotor locally, but no luck on plug wires. I have a Sierra set coming from Amazon but won't arrive until Saturday.

While talking to the parts counter at a Mercruiser dealer, I was told they don't stock wires and "most" people just go to an auto parts store and get "cut to fit" wires. Didn't sound right and not planning to try that. I assume standard wire sets wouldn't be long enough, and I'd think anything conveying a spark would be best left to a marine application.

 

[alldodge]

Wires are wires (auto or marine) but the marine ones are longer because the wires go under the exhaust. Many do get the cut to fit and if you get a good set there is no issue.

 

[Kdubsc]

Wires are wires (auto or marine) but the marine ones are longer because the wires go under the exhaust. Many do get the cut to fit and if you get a good set there is no issue.

I may at least try that on the coil wire since that shocked me yesterday. New wires arriving Saturday. Perhaps I overpaid, so may explore the other options and have the boat running for the wife sooner.

I thoroughly inspected the cables from the battery. Installed all new connections at that end. Removed both from ground post and starter for inspection. No obvious issues, so just cleaned them good. Putting new rotor and cap on this evening. Maybe I get lucky. On muffs this morning, I couldn't replicate the voltage drop and cut off with trim pump. What I did find was the motor stumbled a bit when I tugged the cannon plug. Its not clamped on at all, so I'll do something to snug that up. Gonna pull again and clean the devil out of it.

 

[Kdubsc]

New cap an rotor on. Just waiting for new wires to arrive. I noticed the RPM at idle was lower and had to adjust back up to 650. Before doing that it did shut off a time or 2. No problems after adjustment. Of course, time on the water will tell the story.

 

[Lou C]

I've polished battery connections, checked the ground connections at the back of the engine, checked ignition switch for loose wires, etc. I do still have wingnuts at the batterh, although they're tightened by pliers. A lot more to check im sure, but I'm close to giving up the driveway mechanic work.

Only electrical change before this started was a shop replacing trim sender and limit components. Not sure if they could pinch and short, but I've checked what I can see and don't notice anything abnormal.

get rid of the wingnuts, and buy a set of automotive style but marine grade battery clamps to start with, bolt them on your cable terminals now you can use the large battery posts just like in your car. Next take a look at the terminals for the trim system both at the motor and trim relays. Make sure the terminals are clean and free of corrosion. Lastly try this, put a volt meter across the + and - terminals at your fuse box, should see battery voltage, then turn on the ignition, now what do you see? Same or does it drop?

 

[Kdubsc]

get rid of the wingnuts, and buy a set of automotive style but marine grade battery clamps to start with, bolt them on your cable terminals now you can use the large battery posts just like in your car. Next take a look at the terminals for the trim system both at the motor and trim relays. Make sure the terminals are clean and free of corrosion. Lastly try this, put a volt meter across the + and - terminals at your fuse box, should see battery voltage, then turn on the ignition, now what do you see? Same or does it drop?

I intended to at least go to stainless nuts. May try the traditional clamp if all else fails. As for the trim, it is wired directly to battery, both positive and ground. I did take the relay wiring off and cleaned it.

I'm not sure I have a traditional fuse box. At the helm, all I seem to have are several breakers (one next to key, one next to 12 volt outlet, and a couple at the bank of accessory switches). About the only other fuses I've noticed are blade style fuses in line at the battery and one on the trim pump assembly. I'll look around more and see what I can find.