RE: Issues with Mercruiser 5.0 LX 4 Barrel Carb

[BusinessConnected]

Check for melting where the lower cable runs next to the exhaust

May be time to replace it, they're good for 5-10 years on average

I'll try and take a look.
I've tried adjusting the Throttle Cable today and felt like I had it in a good spot.. But now the Bloody Engine won't start..

Even the usual Forward/Backwards etc reset procedure to override a Gear Box Based Stall isn't working...

It's 8pm Melbourne, Australia Time... I've owned this boat since November 2022.

I've spent probably 200+ Hours on it now.. As in
3 Hours Under its own Power
2 Hours getting towed back to Boat Ramp
1 Hour Spent at Geelong Pier trying to start it when it wouldnt.
195 Hours Fucking around with it getting it repaired.. Replace Head Gasket, Intake Gaskets, Risers etc etc etc..

On top of all of that I've given up Alcohol this year and I've just about had enough

 

[Scott06]

I'll try and take a look.
I've tried adjusting the Throttle Cable today and felt like I had it in a good spot.. But now the Bloody Engine won't start..

Even the usual Forward/Backwards etc reset procedure to override a Gear Box Based Stall isn't working...

It's 8pm Melbourne, Australia Time... I've owned this boat since November 2022.

I've spent probably 200+ Hours on it now.. As in
3 Hours Under its own Power
2 Hours getting towed back to Boat Ramp
1 Hour Spent at Geelong Pier trying to start it when it wouldnt.
195 Hours Fucking around with it getting it repaired.. Replace Head Gasket, Intake Gaskets, Risers etc etc etc..

On top of all of that I've given up Alcohol this year and I've just about had enough

Unplug the shift interrupt switch if it wont start . You may have adjusted it to where it is now tripping the swtich qnd cutting off the ignition. Had a hung up shift swivel arm … tried to adjust the cable onky to have it not start…

 

[Lou C]

I'll try and take a look.
I've tried adjusting the Throttle Cable today and felt like I had it in a good spot.. But now the Bloody Engine won't start..

Even the usual Forward/Backwards etc reset procedure to override a Gear Box Based Stall isn't working...

It's 8pm Melbourne, Australia Time... I've owned this boat since November 2022.

I've spent probably 200+ Hours on it now.. As in
3 Hours Under its own Power
2 Hours getting towed back to Boat Ramp
1 Hour Spent at Geelong Pier trying to start it when it wouldnt.
195 Hours Fucking around with it getting it repaired.. Replace Head Gasket, Intake Gaskets, Risers etc etc etc..

On top of all of that I've given up Alcohol this year and I've just about had enough

that's an unfortunate reality of old boat ownership...I had a running problem and shifting problem with my OMC Cobra both of which I tried to fix but back then I didn't have the knowledge to do so luckily there was still a very good OMC mechanic who fixed both (bought it in 2002, this was in 2004), and no more problems with either one (one was the classic sticky Cobra shifter, easily fixed, the other was a rusty anti siphon valve, also easily fixed) all these years later. The only other problems I've had were typical old boat problems not hard to figure out. Believe it or not I'm still running the same shift cable. Shifts with 2 fingers. Must have been a good supplier!

 

[BusinessConnected]

Haven't completely solved this one yet... But did the "Air, Fuel' Spark" test and saw Fuel flowing into Carby by disconnecting Fuel Line and running into Small Bag..
Air seems fine based on Flame Arrestor being ok..

Followed some Wires back to Battery and found these wireless disconnected from 12V Terminal..

 

[dubs283]

Broken wire aside you need to get rid of that post clamp and get a real battery with threaded posts

 

[BusinessConnected]

Broken wire aside you need to get rid of that post clamp and get a real battery with threaded posts

There's actually a better Battery with Threaded Posts next to it (Optima Marine etc) however that's the designed 2nd Battery....

I'm doing a bit of an "Electrical Engine Audit/Refit" now with New Genuine Disty/Rotor/Sensor etc.

 

[dubs283]

There's actually a better Battery with Threaded Posts next to it (Optima Marine etc) however that's the designed 2nd Battery...

I've found optima batteries to be one of the most unreliable brands out there, ymmv

 

[Baylinerchuck]

Take heart friend. Older boats require patience and TLC. You’re learning along the way, and that experience is invaluable.

 

[BusinessConnected]

Take heart friend. Older boats require patience and TLC. You’re learning along the way, and that experience is invaluable.

It's a good learning curve... and the benefit is that obviously I have a much better idea of how things are put together when it comes to troubleshooting in the future, so in some ways its a good thing. Honestly the most frustrating thing is just the waiting for parts to arrive.. Everytime you discover something its 2-3 days minimum until you can work on it again.

 

[BusinessConnected]

Bit of an update..
Replaced the Distributor Cap, Ignition Sensor and Rotor with genuine QuickSilver Parts.. Boat Initially sprang to life after about 2-3 cranks and ran for around a minute until I attempted to slip into gear again and cut-out.

(Figured by Alignment is still out).

After this and Shifting the Gear Lever Forward/Backwards etc to reset any cut-offs etc... It doesn't crank again.

I've then replaced the Ignition Coil with a New One... Same Result.
It's bizarre to me that it can run for a little while and then just stop..

Any other ideas?
I'm beginning to lean towards the Thunderbolt Ignition Module on Back of Distributor at the moment.

 

[dubs283]

Boat Initially sprang to life after about 2-3 cranks and ran for around a minute until I attempted to slip into gear again and cut-out.

(Figured by Alignment is still out).

Has nothing to do with alignment, it's most likely the shift interrupt switch engaging incorrectly due to a worn/faulty lower shift cable

When you say motor doesn't crank do you mean it won't turn over or won't start/run?

 

[BusinessConnected]

Has nothing to do with alignment, it's most likely the shift interrupt switch engaging incorrectly due to a worn/faulty lower shift cable

When you say motor doesn't crank do you mean it won't turn over or won't start/run?

Shift Interrupt Switch doesn't seem to influence the process, I can disconnect that entirely and there is no change.

Basically the Engine Turns Off and almost starts.. even appears to show Oil Pressure getting up to 40PSI and above but doesn't run ongoing..

I had a bit more of a fiddle and disconnected/cleaned and reconnected the Cables going to the Thunderbolt IV Control Module on Rear of Distributor and seems to be starting again now (unfortunately light got the better of me today).

I'll have a closer look tomorrow. Have Genuine Quick Silver Spark Plug Leads to fit also

 

[Scott Danforth]

Shift Interrupt Switch doesn't seem to influence the process, I can disconnect that entirely and there is no change.

Basically the Engine Turns Off and almost starts.. even appears to show Oil Pressure getting up to 40PSI and above but doesn't run ongoing..

I had a bit more of a fiddle and disconnected/cleaned and reconnected the Cables going to the Thunderbolt IV Control Module on Rear of Distributor and seems to be starting again now (unfortunately light got the better of me today).

I'll have a closer look tomorrow. Have Genuine Quick Silver Spark Plug Leads to fit also

Oil pressure gauge is a different circuit and sender than the oil pressure switch used in the fuel pump circuit

 

[dubs283]

Just to be sure when you disconnect the shift interrupt is it at the shift plate mounted to the engine/riser?

Long thread and forget all that's been done but have you checked/replaced the spark plugs? Firing order correct? Check/set timing/idle?

 

[BusinessConnected]

I've got it starting reliably now, and adjusted Shift Cable so it's engaging forward and reverse etc..
The Miss I seemed to have has fixed itself when replacing Cheap Ebay Leads with New QuickSilver ones.
(The Ebay ones were ok... but they can't handle the amount of times I've pulled them off/on etc).

Looking forward to a Test on the water later in the week.
I've got a spare V8 Thunderbolt Control Module (V8 22/24 Advance (Can't remember but its the same as mine) coming...

I want that on me so if I have dramas with things on the water I can swap it out...

 

[Scott06]

The Miss I seemed to have has fixed itself when replacing Cheap Ebay Leads with New QuickSilver ones.

Looking forward to a Test on the water later in the week.
I've got a spare V8 Thunderbolt Control Module (V8 22/24 Advance (Can't remember but its the same as mine) coming...

I also keep a spare module in the boat. Used one off ebay. Probably buying it will ensure I will never need to use it...

So the plug wires were bunk?

I've stopped buying most aftermarket items too many bs stories like this lately.

 

[Scott Danforth]

I also keep a spare module in the boat. Used one off ebay. Probably buying it will ensure I will never need to use it...

That is the logic I have with the ignition module, impeller kit, fluid kit, and the spare drive. Just not carrying the drive onboard.

 

[BusinessConnected]

That is the logic I have with the ignition module, impeller kit, fluid kit, and the spare drive. Just not carrying the drive onboard.

I'm learning that this is a good insurance policy..
I actually managed to pick up a Good Used Complete Distributor Rod/Cap/Rotor complete with the Ignition Module.

That's getting wrapped up in Bubble Wrap and stored under the Life Jackets

 

[BusinessConnected]

I'm back to intermittent starting again yesterday... Would start once in the morning and then not kick in again..
I'm hoping this is all a Dodgy Ignition Module... Hopefully that resolves by issues when it arrives.

 

[Scott06]

I'm back to intermittent starting again yesterday... Would start once in the morning and then not kick in again..
I'm hoping this is all a Dodgy Ignition Module... Hopefully that resolves by issues when it arrives.

Do you have spark when it doesn't fire, test with a spark gap tester off the coil and at the plugs