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4.3L Mercruiser Just quits....Please help

A

ApexerER

New member
Last year I purchased a 2000 Regal 2100 LSR with a 4.3L that had a spun main bearing. I purchased a long block and while I was at it I figured I would throw on a Edelbrock Intake and 4bbl. I replaced all the plugs, wires, cap, rotor, ign coil, hoses, belts, fuel filter etc. Basically anything I thought might give me a problem. Boat ran flawlessly all summer. Last Sept I had it out and it ran fine all day. As I was heading back to the launch and the boat just quit at about half throttle. I thought I ran out of gas since I had never run the boat down below half a tank, I figured the fuel gauge wasn't working. Waited a couple of minutes and fired it back up, it ran great for about 30 seconds and died. I made it back to the launch, pulled it out of the water, went to the gas station, threw 30 bucks in it and went back to the lake to make sure I didn't have a problem. Fired it up, ran it out on to the lake, ran perfect for 2-3 min and quit. Made it back to the launch with the boat running fine and quitting for about 30 seconds at a time. Figured I must have gotten water in the fuel. A few days later I changed the filter, brought a spare with me and headed back to the lake. Fired up the boat and it ran perfectly. Ran the boat for what had to be about 6-7 miles (around the lake) and just as I am thinking ok she is all set, it quits. WTF...I change the fuel filter while I am out on the water thinking there is water in the gas and it clogged the filter. Change the filter, boat fires right up, I hit the throttle, its running perfect, no bog etc...I make it about 100-200 yds and it dies again. Make it back to the launch with it running for about 30 seconds at a rip and take it home. Fire it up in the drive way. It runs fine for at least half an hour on the ears. (ok this is driving me crazy) Finally it quits...I immediately pull the fuel line and see if the fuel pump is pumping. It fills a two liter bottle very fast. More than fast enough to keep the carb full. Ok its not the fuel pump. I have the fuel tested by a buddy of mine. Fuel tests fine. No water etc. This is as far as I have gotten and I am not sure where to go from here. I had to winterize the boat and put it in storage. I am getting it out this week and want to get this straightened out.....I have been thinking about it all winter and still don't really know where to start. Could the ECU be getting hot? Please give me some ideas
 
1. check fuel tank vent line.if clogged a vacuum will occur and stop fuel flow...........ie changed filter (relived vacuum) and it ran good for a while.

2. if that is not the issue the get a separate gas tank and connect it to the fuel line at the fuel/water seperating filter. where the inboard tank connects.

see if this corrects the issue.

also check to see IMMEDIATELY after it stalls to see if gas shoots out of the accelerator nozzles. If no gas then no gas in carb. either carb issue (possible float height or needle sticking)or gas flow issue.

If none of the above look at ignition........WHat coil did you use? Internal or external resistor or factory replacement (internal resistance)?
 
kghost said:
1. check fuel tank vent line.if clogged a vacuum will occur and stop fuel flow...........ie changed filter (relived vacuum) and it ran good for a while.

2. if that is not the issue the get a separate gas tank and connect it to the fuel line at the fuel/water seperating filter. where the inboard tank connects.

see if this corrects the issue.

also check to see IMMEDIATELY after it stalls to see if gas shoots out of the accelerator nozzles. If no gas then no gas in carb. either carb issue (possible float height or needle sticking)or gas flow issue.

If none of the above look at ignition........WHat coil did you use? Internal or external resistor or factory replacement (internal resistance)?
Click to expand...

Thank for your response....Never thought about fuel tank vacuum.....That would be awesome if that was the case...Coil is an internal resistance...
 
If you can access the vent line where it is attached to the gas tank then remove and blow it out........better than blowing any crud into tank.
 
You say you replaced the filter.

which one?

There is or may be a water separating filter and there may also be a filter at the carb. Have you looked for that? if not look!
 
I am seeing several posts describing this same or similar symptom. My symptoms today are almost the same as yours. I am on my 3rd fuel pump ( Sierra 18-7326). Today after running the heck out of my 4.3L '95, she starts that familiar choke, spit, pop, pull back in the thottle, lower, lower, finally she gives up. Let it sit for 5 minutes and she'll fire up and take me a mile down the river again before she quits. Seems temperature related like the pump fails when the engine heats up. Or something else is failing when the engine heats up and effects the pump voltage. The longer I let it sit, the longer it will run before quitting. Jack, does that help narrow it down any? Apex does this seem the same as yours?
 
Also, I noticed that while she was struggling to stay running ( or starving for fuel ), that if I operated the Trim ( which pulls voltage ) it would nearly stall out the engine. Mean anything?
 
BassAckwards said:
I am seeing several posts describing this same or similar symptom. My symptoms today are almost the same as yours. I am on my 3rd fuel pump ( Sierra 18-7326). Today after running the heck out of my 4.3L '95, she starts that familiar choke, spit, pop, pull back in the thottle, lower, lower, finally she gives up. Let it sit for 5 minutes and she'll fire up and take me a mile down the river again before she quits. Seems temperature related like the pump fails when the engine heats up. Or something else is failing when the engine heats up and effects the pump voltage. The longer I let it sit, the longer it will run before quitting. Jack, does that help narrow it down any? Apex does this seem the same as yours?
Click to expand...

Sounds very similar. Mine will not go a mile once it happens. Hopefully with the weather nice at the end of the week I can get back on it and solve the problem
 
..."Also, I noticed that while she was struggling to stay running ( or starving for fuel ), that if I operated the Trim ( which pulls voltage ) it would nearly stall out the engine. Mean anything"

Sounds like low voltage. Bad alternator or loused up connections somewhere.

Jeff
 
Ok, I finally got to spend a little time with the boat on Saturday afternoon. I ran the boat for at least 45 minutes in my driveway. Ran perfectly fine. Revved up, no skipping, smooth idle, like nothing is wrong. I take the boat to the lake. Starts right up at the launch, runs flawlessly leaving the no wake zone which is about 1/2 mile long going past all the marinas. Get past the no wake zone and punch it. She jumps up on plane and takes off revving up flawlessly. I make it maybe an 1/8th mile. I lose power, bring her down off plane, its barely running and quits. I immediately check for fuel and there is fuel from the secondary squirters. Pull the coil wire off the center of the dist cap and check for spark. It has spark. Put wire back on and fire it up. Runs perfect for maybe 30 seconds and then loses power and quits. I check for spark again at the ignition coil wire. It has spark but it is a weak orange spark. Check for spark right at coil and it is a bright blue lightning bolt. Hmm...Use a test light since I don't have an OHM meter with me and the test light will not light going through the coil wire. Limp back to the launch, take the boat home and make a new coil wire. Check with a test light and it lights up. Yatzee I got it...yes. I put the coil wire on and fire the boat up in the drive way and it runs fine. I take the boat back to the lake, dump it off in the lake and it almost immediately acts up. So its late so I put the boat on the trailer and take it back home. At this time I am thinking that my bad coil wire burned up my coil and it would work until there was any sort of load. I am going to steel the Coil off my buddies racecar and give that a try ASAP before I purchase a new one just to be sure. Does this sound reasonable?
 
Thunderbolt coils are internaly resistered.
You gan get a new one from an auto store for around $20

The key is internal resister coil. And put a new set of OEM wires on it!!
 
Don't waist your money

My internally resistor coil in my 1987 boat is original and still works fine!! TB IV

You don't have a special ignition requiring a special "high output" coil or a special boat either...........

save the $30 and buy new wires they will cost around $70.00 for OEM...............
 
kghost said:
Don't waist your money

My internally resistor coil in my 1987 boat is original and still works fine!! TB IV

You don't have a special ignition requiring a special "high output" coil or a special boat either...........

save the $30 and buy new wires they will cost around $70.00 for OEM...............
Click to expand...

The wires are brand new which is why I didn't originally look at them. That coil wire must have been bad from the start and I am thinking the coil was pushing through the wire until it burned out...
 
My problem is fixed!! I did replace my coil, wires, dist cap and rotor. However I also changed the thermostat and the impeller. It was running 180 on a 170 thermo. I dropped in a 143 deg thermo, and now she tops out at 170 degrees and no more problem. I took her out in the cheasapeake and really ran her hard with no probs. What is your normal operating temp? it may be high enough to be shutting down your motor.
 
Would definitely pay to eliminate the fuel tank as an issue, it does sound like fuel trouble. Run a hose from a clean tote tank to the fuel pump (or even direct to carb if you can keep the tote level with or above it). Plug/pinch the boat tank hose and using zip ties/duct tape/whatever, route all hoses away from heat and pulleys etc. (Don't ask me why I mention that one :|)

I had very similar problems to yours, long story short ended up ripping up the floor and removing the tank to find a little bit of crud in there but also a ~1/4" short bolt tumbling around in there - with a head similar size to the fuel pickup. My theory was it would run fine in the drive way, but getting up to speed on lumpy water, the bolt would eventually find its way to the fuel pickup and starve the engine. Once engine was stopped and fuel demand removed, the pickup dropped the bolt, and it was good to go for a little while again.

Not a hard diagnosis to perform anyway. Could be worth running with the flame arrestor off too, have someone drive it and blast a squirt of ether down its gob as soon as it starts playing up. If it comes right/changes for a moment you know you almost certainly have a fuel delivery issue.
As for trimming while playing up - trim motor swings on the alternator fairly heavily, its probably just the extra load killing it.
 
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For everyone following along this thread....I replaced the Ignition sensor in the Distributer and it fixed my problem. Thankfully a very simple and inexpensive part. I wish I had just replaced this sensor when I put the engine in with all the other electrical components. Stupid little thing spent a lot of time driving me crazy. I will keep that in mind and replace that sensor whenever I do a tuneup....
 
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