Knock sensor causing my boat to not run?

[Onelovedex]

Just purchased a 2008 Tige Z1 with the 5.7L Vortec 340 v drive. Took it out on the first run last night. Ran great for an hour or so pulling kids on tubes, wakeboard, etc. Close to sunset we stopped for one last change of wakeboarders before we were going to head in. While idling the boat sputtered and turned off. I waited about 3-4 minutes and tried to start again. The first time it would turn over and run for about 2 seconds before sputtering off. My immediate second try it would not turn over, just the starter engaging. If I waited about 3-4 minutes this same process would repeat. After a few phone calls to friends i ended up going two things. 1) I pulled the distributor cap plug off and pressed back on firmly. 2) I could loosen the knock bolts by hand which I was told should not be able to happen. I unplugged the knock sensor connector, blew in it, and reconnected firmly. Then tightened the bolt with my hand as hard as I could. I repeated this on the other side. Gave it a few minutes and the boat started right up and ran like it did before.

Has anyone else experienced this? I thought the knock sensor would only diminish the power, not stall the boat out completely. Or perhaps it was the distributor plug that fixed it?

[UNSTUCK]

This all sounds strange to me. You say the starter will engage, but the engine does not turn over. So you heard the starter "click", but nothing happened after that? That tells me you have low battery voltage. That could explain why it died while idling the first time. When batteries sit for a bit they do a bit of self recharge, which could have let you get going again that last try. Maybe your alternator isn't putting out enough at idle speeds, but will when at cruising speeds.
I'm not positive, but I think knock sensors are inactive in most situations during open loop, which I believe lasts at least 30 seconds at each start up. Longer if the engine is cold. My guess is playing with knock sensors allowed enough time for the batteries to charge themselves enough to get things running again. I'd at least keep an eye on your batteries. Check voltage at the batteries and also at the starter motor. Make sure the numbers are at least very close, if not the same.

[Onelovedex]

Thanks Unstuck I will give that a try tonight and post back what I find. The guy I bought the boat from claims he has been using it this season with no problems.


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[h2o-ski]

On my old 05, I once forgot to plug the knock sensor back in after I changed the oil. The engine ran fine for some time, then it would start beeping at me. There were no ill affects in the short time that the sensor was unplugged. From my understanding on 05 MP 5.7 was that the ecu would slowly advance the timing until it started to hear knocking. Once the knock was detected, it should retard timing until no more knock is heard. In my case I'm assuming that with it unplugged, it reached max timing then started beeping.

[Onelovedex]

Unstuck you are on to something. It was not the knock sensors. It’s not electrical. This has happened 3 times now. It is always after idling in one spot or idling out of my long cove to the main channel. After about 10 minutes of waiting the boat cranks and runs like a champ. Could it be getting flooded? Is that possible with a fuel injected engine? Vapor lock?


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[UNSTUCK]

I for one, am still confused about your "would not turn over, just the starter engaging". If the engine cranks over and over without starting you may have a fuel issue. If the starter just makes a single click, or even several fast clicks you have a voltage issue. Take a meter with you next time and when it happens take voltage readings at the battery (with everything off), at the starter battery cable (with everything off), at the alternator (with everything off) and again at the starter while someone is actively holding the key switch in the crank position.

After waiting your few minutes and it's running again do the same voltage checks: at the battery, the starter battery cable and alternator....all at idle speed. Then do those again with the boat in neutral and say, 1500 RPM.

Everything off should be right around 12.5 volts at the batteries and maybe just a bit less at the other spots.
Running at idle speed should be at least 13.5 volts.
High idle speed should be at least 13.5, but likely a little higher, but not over 14.5 volts.


Fuel injected boats are less susceptible to vapor lock due to higher pressures, but can still happen and the symptoms sound right, if you are in a crank but wont start scenario. If it will crank over fine, but not start you could have "flooding". Fuel injection wont flood an engine like you are used to on a carburetor. Fuel injection can really only flood an engine if an injector is stuck open. "Pumping the gas pedal" does nothing. This brings us to your spark plugs. What do they look like? Very doubtful they are bad, but you could have a couple injectors sticking open and pouring in fuel witch fouls them for a bit till they dry out. Then the engine fires up. You'd still get the other cylinders firing when trying to start though.

Let us know.

[Onelovedex]

Ok finally was able to get on the water with my voltmeter. The boat did the same thing yesterday. Idled out of my cove fine. Took a 15 drive to marina to get gas. Idled into the cove fine. Filled up the tank and idled back out of the marina cove. Went to give it throttle and it was sputtering not wanting to go. Could give it full throttle and nothing happened just sputtering. I could feather the throttle right above neutral to keep it going somewhat but it ended up dying out. I started my watch timer. Battery was at 12.4. Starter was at 12.2-12.4. I couldn’t get my alternator to read at first. 2 things I noticed. 1) it looked like the ground wire from the alternator was just hanging in the air not attached to anything. 2). I put the red on the alternator and the black down on an engine mount bolt to ground it. It was reading .14? After 14 minutes of drifting the boat started right up. Drove about 4 minutes then stopped to surf. As I was pulling up the rider the same issue, engine sputtering and quit. Waited 15 more minutes and it started again. Ran it hard for 10 minutes then surfed another hour with no problems. But I did always turn off the engine instead of idling when switching riders. Ran back to my house and into the cove no problems.


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[Onelovedex]

Talked to a friend and he said maybe the ball in the fuel line was going bad and letting fuel back into the tank and not keeping the fuel pump primed?


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[Onelovedex]

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[jeepcj258]

Onelovedex Did you ever figure this out?

[dukeoka]

Unfortunately, because of this problem, I sold my boat point.

[boatwakes]

Probably because you're a booger eater.

[dukeoka]

Unfortunately, because of this problem, I sold my boat point. I was constantly running into various issues and was getting tired of fixing this boat. Recently when we were on holiday with my wife in Miami, she suggested we rent a boat. Since I know how to drive all boats, it was no problem for me, so we a boat rentals miami. I will tell you the truth, this vacation will be remembered for the rest of my life, and now I dream of buying my boat. But most of all, I love the fact that I make my itinerary that doesn't depend on any schedule, and I don't have to make any stops. I'm looking forward to my next holiday to go to Miami mi-e to rent a yacht again but with my friends.