Still chasing hard warm starting, 7.4 carbed

[tango13]

1995 7.4, carbed. New block and bottom ends, 30ish hrs. Last season I battled hard start/no start when hot. Engine would crank but not fire after warming up. The boat was new to me, so I hadn’t figured it all out yet, but my old boat with a 350 would start with a bump of the key every time.

I never did figure out if it was spark or fuel, so started with a few items before the season started. My batteries were shot so I did two new 1000 crankers. Replaced ignition sensor (took apart old one and it was caked in rust), cleaned flame arrestor, and did new plug wires (coil wire was corroded so bad in coil that I had to pull out with pliers). Cap and rotor were good. Pulled a few plugs and appeared to be good. Also wrapped the fuel lines in header wrap, plus rubber hose as I struggled with ruling out Vapor lock, which I believe is not the case as I have cool lines and have been running ethanol free fuel.

Took it out and it ran WAY better, but it gave me that never ending crank/hard start after running all day. Brought a spark tester with me and confirmed I had spark. Got it to catch after just cranking it for 10-15 seconds. Awesome. I’ve been playing around and doing lots of reading, and tried the whole WOT when starting. It did work and I get a big puff of black smoke once it got going, though I was pumping the crap out of it at first and obviously I flooded it from that. Also just tried cranking on it with no throttle and after about 8-10 seconds it starts to catch and go. Been doing the latter procedure for the last couple weeks and it’s been consistent. I pulled the flame arrestor one day to watch the choke (which I think works fine) and noticed the carb was dribbling fuel from the Venturi while idling. Not sure if that’s normal but from what I’ve read they shouldn’t do that (it’s a carter/Weber 4 barrel). It didn’t dribble at shutdown but I didn’t wait around long enough to watch. My symptoms almost seem like it’s running a tad rich and then flooding at shutdown. When it’s cold, it fires right up so I know my fuel bowls aren’t evaporating/dry. Does this make sense?

Next step I’m thinking is a carb rebuild, I wonder about the needle not seating as maybe something got in while it sat on a bench during the motor job. Also contemplating a fuel pump but I’m not getting any other symptoms and I haven’t confirmed pressure. Boat runs awesome when it’s running, absolutely perfect. One thing I have noticed is that the boat gets super smelly with exhaust when it’s idling (thru prop exhaust) but it never seems to load up as if it was flooding bad that could just be me not being used to a big block?

 

[SDSeville]

Is your fuel line from the pump to carb clear or see thru? I had this problem with a Merc 3.7 and when warm, the pump would continue to pump after I shut down, causing flooding condition. I tried multiple batteries to crank thru the flooding and worked ok. I finally noticed the continued fuel after shut down and replaced the fuel pump with an new electric pump and it started perfectly. ...just a little bump from the stater and fired right up. May not be your problem but sure made my boating days better.

 

[tango13]

Is your fuel line from the pump to carb clear or see thru? I had this problem with a Merc 3.7 and when warm, the pump would continue to pump after I shut down, causing flooding condition. I tried multiple batteries to crank thru the flooding and worked ok. I finally noticed the continued fuel after shut down and replaced the fuel pump with a new electric pump and it started perfectly. ...just a little bump from the stater and fired right up. May not be your problem but sure made my boating days better.

It’s a steel line. Looks like the original pump, but It’s a mechanical fuel pump so I’m not sure how they continue to pump when shut down?

 

[kenny nunez]

Next time try adding a jumper wire from the + or bat on the coil to the + battery terminal before you try to start. If it starts better than the bypass circuit from the started solenoid is not active.

 

[tango13]

Next time try adding a jumper wire from the + or bat on the coil to the + battery terminal before you try to start. If it starts better than the bypass circuit from the started solenoid is not active.

Just weird that it fires immediately when cold and after it sits for a few hours

 

[kenny nunez]

Believe it or not but I have seen the symptom you are describing act that way. That was one of the first things I always checked on a tune up job.

 

[Scott Danforth]

Check fuel pressure and choke setting

 

[dubs283]

'95 carbureted, weber, 454 guessing thunderbolt ignition wouldn't require ignition bypass.

Might be gen v but crossover/vintage inventory could be iv, won't know without pictures

Good news for OP the dribbling venturis mean no harm to the (30 hr?) short block. Heads not sent out for valve job?

Tune up is important, hopefully the only ignition system component not replaced during the redress was the ignition sensor

 

[tango13]

Check fuel pressure and choke setting

What’s the easiest way to check fuel pressure? It’s all steel line so at first glance I’m going to have to remove and make a new rubber line with an in-line gauge

 

[tango13]

'95 carbureted, weber, 454 guessing thunderbolt ignition wouldn't require ignition bypass.

Might be gen v but crossover/vintage inventory could be iv, won't know without pictures

Good news for OP the dribbling venturis mean no harm to the (30 hr?) short block. Heads not sent out for valve job?

Tune up is important, hopefully the only ignition system component not replaced during the redress was the ignition sensor

Only other component that hasn’t been replaced or verified is the coil. I’ll have to pop every plug out and check as I only looked at a few.

 

[tango13]

'95 carbureted, weber, 454 guessing thunderbolt ignition wouldn't require ignition bypass.

Might be gen v but crossover/vintage inventory could be iv, won't know without pictures

Good news for OP the dribbling venturis mean no harm to the (30 hr?) short block. Heads not sent out for valve job?

Tune up is important, hopefully the only ignition system component not replaced during the redress was the ignition sensor

'95 carbureted, weber, 454 guessing thunderbolt ignition wouldn't require ignition bypass.

Might be gen v but crossover/vintage inventory could be iv, won't know without pictures

Good news for OP the dribbling venturis mean no harm to the (30 hr?) short block. Heads not sent out for valve job?

Tune up is important, hopefully the only ignition system component not replaced during the redress was the ignition sensor

And yes thunderbolt ignition. Bravo drive. Unsure if the heads were done. Are the venturies dribbling normal? From what I’ve read about carter/eddy carbs, they shouldn’t be doing that at idle.

 

[dubs283]

Unsure if the heads were done.

Are valves adjusted proper?

Weber carb should not dribble at idle. There is many check items that can cause this starting with fuel supply and ending with exhaust

 

[kenny nunez]

Is the timing set? There should be no dribbling at idle on any carburetor fueled engine. You need to start making sure the carburetor is clean with a rebuild kit. Also check that the throttle shaft is not twisted and the blades close tight in the body. 1to 1.5 turns on the idle stop screw. Any more and the next circuit is coming on. Sometimes drilling a !/64” hole in the primary butterfly plates and with a vacuum gauge for setting the idle mixture and gradually drilling larger holes until the idle stop screw keeps the next circuit off. The mixture screws most time end up at 1.5 turns out from the bottom.

 

[tango13]

Is the timing set? There should be no dribbling at idle on any carburetor fueled engine. You need to start making sure the carburetor is clean with a rebuild kit. Also check that the throttle shaft is not twisted and the blades close tight in the body. 1to 1.5 turns on the idle stop screw. Any more and the next circuit is coming on. Sometimes drilling a !/64” hole in the primary butterfly plates and with a vacuum gauge for setting the idle mixture and gradually drilling larger holes until the idle stop screw keeps the next circuit off. The mixture screws most time end up at 1.5 turns out from the bottom.

Timing was confirmed. Thanks for the info on the dribbling, That was my understanding as well.

 

[tango13]

Are valves adjusted proper?

Weber carb should not dribble at idle. There is many check items that can cause this starting with fuel supply and ending with exhaust

No clue about heads, they run quiet so i'm assuming? Motor was built by a reputable builder. Thanks for info on the carb

 

[SDSeville]

It’s a steel line. Looks like the original pump, but It’s a mechanical fuel pump so I’m not sure how they continue to pump when shut down?

Mine had a crack in a bladder or something inside the pump that allowed fuel continue to flow after shutdown. If I let it sit 20-30 minutes, it would start right up.

 

[tango13]

Mine had a crack in a bladder or something inside the pump that allowed fuel continue to flow after shutdown. If I let it sit 20-30 minutes, it would start right up.

Interesting, could be worth throwing a fuel pump at regardless, given it's age

 

[tango13]

Sorry to the moderators for posting on an old thread but I would provide an update on this for anyone in the future. Boat started like crap when all all summer in 2023. That fall before I winterized it, I took off the ignition coil and it was nasty - the socket was full of corrosion, and the canister was rusted bad. Replaced with an
MSD #8222.

Fast forward to spring. I took it to a new mechanic and explained the symptoms. He too thought maybe fuel and ran the crap out of it in his test tank, and could not get it to replicate the issue. I’ve been running it hard in HOT days this summer, and it’s been running and starting 1000 times better. Feels like a whole new motor. Not sure if it was the coil or the connections or both, but it worked.

 

[Bondo]

Sorry to the moderators for posting on an old thread but I would provide an update on this for anyone in the future. Boat started like crap when all all summer in 2023. That fall before I winterized it, I took off the ignition coil and it was nasty - the socket was full of corrosion, and the canister was rusted bad. Replaced with an
MSD #8222.

Fast forward to spring. I took it to a new mechanic and explained the symptoms. He too thought maybe fuel and ran the crap out of it in his test tank, and could not get it to replicate the issue. I’ve been running it hard in HOT days this summer, and it’s been running and starting 1000 times better. Feels like a whole new motor. Not sure if it was the coil or the connections or both, but it worked.

Ayuh,..... No worries, it's yer thread,.... Thank you for the update,.....

 

[Scott Danforth]

Well, this is only the 4th coil that I know of that may actually have been bad