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SkiBoy
08-17-2011, 05:29 PM
99 outback LS 5.7 350

Knock started out of the blue. Skied twice, let the boat sit for 45 minutes and then the noise started under load.

Lean knock was the consensus from several people. Had a mechanic come out and he said the same thing. Thought it was bad fuel, and running lean.

Rebuilt the carb, new plugs, cap, rotor, changed oil and all filters. Ran all the old gas out of it with the timing retarded. (This kept it from knocking) Lost power, but was able to run the boat out of fuel. Put 25 gallons of 93 octane in and advanced the timing a bit, no knock, more power. Advanced again and the knock came back.

Any ideas or hints? This is driving me crazy. Boat was idling poorly all year, still does. It didn't after new plugs, etc for a while but is again. I pulled the plugs, old and new, and they seem in good shape.

mmandley
08-17-2011, 11:48 PM
Heres some info i found for you. Sounds liek you need to check out a few things on the boat to help narrow it down.

Mild detonation can occur in almost any engine and will not cause damage. Prolonged heavy detonation can crack pistons and rings, blow out head gaskets, damage spark plugs and valves, and flatten rod bearings.

Any of the following can cause detonation:

^ Too Much Compression: An accumulation of carbon deposits in the combustion chambers, on piston tops and valves can increase compression to the point where it exceeds fuel octane rating. If a top cleaner fuel additive fails to remove deposits, a new alternative is to blast the deposits loose by blowing crushed walnut shells through the spark plug hole. Otherwise, the head will have to be removed so the deposits can be scraped off.

^ Overadvanced Ignition Timing: Too much spark advance causes cylinder pressure to rise too rapidly. If resetting the timing to stock specifications does not help, retarding timing a couple of degrees may be necessary to eliminate knock.

^ Engine Overheating: A hot engine is more likely to suffer spark knock than one which runs at normal temperature. Overheating can be caused by low coolant, a defective fan clutch, too hot a thermostat, a bad water pump, etc. A buildup of lime and rust deposits in the head and block can also reduce heat transfer.

^ Overheated Air: The thermostatically controlled air cleaner provides the carburetor with hot air to aid fuel vaporization during engine warm-up. If the air control door sticks shut so that the carburetor continues to receive heated air after the engine is warm, detonation may occur, especially during hot weather. Check the operation of the air flow control door in the air cleaner to see that it opens as the engine warms up. No movement may mean a loose vacuum hose or a defective vacuum motor or thermostat.

^ Lean Fuel Mixture: Rich fuel mixtures resist detonation while lean ones do not. Air leaks in vacuum lines, intake manifold gaskets, carburetor gaskets or fuel injection intake plumbing downstream of the throttle can all admit extra air into the engine and lean out the fuel mixture. Lean mixtures can also be caused by dirty fuel injectors, carburetor jets clogged with fuel deposits or dirt, a restricted fuel filter, or a weak fuel pump.

The air/fuel ratio can also be affected by changes in altitude. A carburetor calibrated for high altitude driving will run too lean if driven at a lower elevation. Altitude changes are generally compensated for on computer cars by the barometric pressure sensor.

A lean fuel condition can be diagnosed by watching for lean misfire on an ignition scope, or by using a four-gas infrared analyzer and watching exhaust oxygen levels. A reading over about 3% to 4% oxygen would indicate a lean fuel condition.

^ Spark Plug Too Hot: The wrong heat range plug can cause detonation as well as pre-ignition. Copper core plugs are less likely to cause detonation than standard spark plugs.

^ Loss of Exhaust Gas Recirculation (EGR): EGR keeps combustion temperatures down, reducing the tendency to detonate. If the EGR valve is inoperative or someone has disconnected or plugged its vacuum hose, higher combustion temperatures can cause pinging.

^ Low Octane Fuel: Burning cheap gas may be one way to save pennies, but switching to a higher grade of fuel may be necessary to eliminate a persistent knock problem.

^ Defective Knock Sensor: The knock sensor responds to frequency vibrations produced by detonation (typically 6 - 8 kHz), and signals the computer to momentarily retard ignition timing until detonation stops. A knock sensor can usually be tested by rapping a wrench on the manifold near the sensor (never hit the sensor itself). If there is no timing retard, the sensor may be defective

SkiBoy
08-18-2011, 10:55 AM
Thanks for the reply.

From top to bottom:

Too much compression - I used Sea Foam to clean carbon deposits in the fuel and poured it directly on cylinders, as per instructions.

Advanced spark - timing was retarded to get rid of knock.

Engine runs at operating range of 160 -170

One vacuum hose, no leaks Engine has additional vents for clean air.

Carburetor rebuilt

Altitude not changed

Plugs are to spec


No egr

Running 93 octane only

No knock sensor

The only thing left on this list is the ignition scope for O2 levels.

kaneboats
08-18-2011, 11:32 AM
Is it possible the 93 is too high? I think your engine is supposed to run on 87 or 89.

Mikes
08-18-2011, 01:00 PM
Did you check the springs on the advance weights in the distributor? If one came off or broke it can cause this to happen.

SkiBoy
08-18-2011, 01:42 PM
I changed the cap and rotor but did not check the distributor itself. Not sure how to check the advance weights. Any hints?

The motor was idling poorly all year, and now it fluctuates from 850 to 1100. After a run it sometimes jumps to 1500 before settling back to 900-1000. The Tach also moves around during operation but does not affect actual speed of the boat. No trans slip, no engine rev noise when the tach runs up or drops. I ski a lot, 3-400 times a year usually at 36 mph. I would feel the speed drop or increase while I'm cutting. I don't feel it, but the drivers see the needle move.

Thanks for your help.

Mikes
08-18-2011, 03:49 PM
The weights are under the trigger wheel and pickup near the bottom of the distributor. Between the tach moving allover and the spark knock its most likely in the distributor,but not allways. If you really ski that much how many hours are on this boat?

SkiBoy
08-18-2011, 04:31 PM
800 hours, and yes I do ski a lot. I live on a small lake in central NY and usually I'm on the water from early May to Late October, skiing 3-4 times a day, on the average 5 days a week.

This boat has been a champ for 12 years. Almost no service problems. Water pump, transmission seals, and a few hoses, and regular maintenance, etc. Nothing else.

I pulled off the rotor and did not see the spring weights. Are they under the wheel that holds the rotor, or below that assembly. Thanks, I'm hoping this is the problem, as I have done just about everything else I can think of.

Mikes
08-18-2011, 04:57 PM
If you cant see them it may not have them the springs are very small. This boat may be too new. Grab the distributor shaft and see if it has any play in it. Can you take a pic of the distributor with the cap off? Also are you sure about vacuum leaks,have you checked it with a vacuum guage? Did you change the plug wires with tune-up?

SkiBoy
08-18-2011, 05:26 PM
It's an electronic distributor. I just went down to see the mechanic that has been helping me and he asked about any play in the distributor. I'll check it. maybe the modules are bad or the whole thing just is out of whack.

We have not checked any vacuum leak with a gauge, just sprayed around the carb and manifold. Did not change plug wires yet. I'm pulling the plugs now to look at them again.

The odd thing to me is that the knock started so suddenly. All my drivers know the sound the engine is supposed to make, and will shut it down if there is a different noise than normal. I also pull skiers now and then and do check rides alone to see how it is performing. There was not an indication that anything was wrong until the first knock was heard, and it was loud and strong enough to make the driver stop before the boat was up to speed.

Thanks

Mikes
08-18-2011, 06:36 PM
Have you noticed a change in the oil pressure? Does the knock get louder as the engine warms up?

SkiBoy
08-18-2011, 07:55 PM
Oil pressure seems fine. Knock is non-existent now due to the retarded timing. The mechanic will advance it tomorrow under load until we hear knocking. The knock was consistent when I was having various people listen and try to diagnose the sound. I always operate at 160 or a hair above after warm up.

Plugs looked okay. I put another set in and it still runs rough. Both sets are a few weeks old. One hotter, one to specs.

Mikes
08-18-2011, 08:30 PM
Are you using a timing light when you try to advance to spec.? I wish I was close to you I really enjoy working on these boats,who knows why after working on them for many years? I would NOT run the hotter plugs for very long!

SkiBoy
08-18-2011, 10:16 PM
Yes, we will use a timing light. Will update after tomorrows testing.

SkiBoy
08-19-2011, 02:14 PM
Mechanic could not make it out today. It will be Monday before he can get here. Any suggestions that could help me out? Thanks

mmandley
08-19-2011, 09:40 PM
Using a timming light isnt to hard, and adjusting the timming on the boat isnt to hard eigher if you want to give it a shot. All you do is losen the bolt holding the distributor down just enough to allow you to turn the distributor. If all your looking to do is ruff tune it for the weekend then get a driver to get the boat up on plane and slowly turn the distributor and you will feel and hear the engine change in rpm and power as the spark timming moves. If your nervouse then you will have to wait. The timming light works the same way but you do the adjustments at idle.

Nice thing about boats is you can dial them in under a real load unlike cars they have to be sitting still or on a dyno.

SkiBoy
08-20-2011, 12:55 PM
We have done that under load and it had to be retarded to stop the knock. I advanced it a bit and it was all good, I advanced a bit more and the knock came back, so I retarded it again. Bottom line is that the timing is retarded about an 1/4 inch from the factory line on the distributor. Why is the knock still there after all I have done?

mmandley
08-20-2011, 08:07 PM
Reread all the posts here and all thats comming to mind is if your still having idle flutuations you got a air leak someplace. Its effecting the vacume side and this is making you run lean. Maybe try running the carb rich for a day and see if that compensates for the lean idle. I used to run my 79 Trans Am real lean at idle to get that shaker hood shaking hard for stop light intimidation but i have the jets in the carb over sized to run rich so when i punched it she drank fuel like i do beer LOL.

If you run it rich and the knock is still there im also concerned with your timming and wondeirng if the timming chain hasnt stretched and its trowing everything off. Not much left on the outside to mess with its looking more and more like a winter rebuild my friend.

SkiBoy
08-20-2011, 09:09 PM
Thanks for the info. We found a bad spark wire tonight. (number 7) It was loose and shocked me when I tried to lift it off. The spark was coming through the black boot when I wiggled the wire on the distributor. I'll replace all of them next week from Indmar, but in the meantime I'll just replace the one and see if it smooths out the idle.

I have a mechanic coming over tomorrow and he is a marine mechanic, so I'll get his opinion as well. We'll check for air leaks again around the manifold and carb. Vacuum hose is good as is the pcv. I want to break it down this winter as well. take the top half off and have a look see. i just want to finish the season without it eating itself. I wondered about the timing chain. I'll ask the guy. Thanks, will report tomorrow.

SkiBoy
08-21-2011, 01:25 PM
Reread all the posts here and all thats comming to mind is if your still having idle flutuations you got a air leak someplace. Its effecting the vacume side and this is making you run lean.

Good call. I checked the two gaskets under the carb by spraying carb cleaner and there was an air leak. When we took off the carb there was carb cleaner under the gaskets. One gasket hadn't even made an impression on the angle block. We used sealer and are waiting for it to set up. Put the regular plugs back in and will test shortly. Will also advance the timing during operation while under load.

Will report back soon.

SkiBoy
08-21-2011, 02:30 PM
Carb is no longer leaking air. It settled down the idle issue a bit. I advanced the timing and the knock came back. We are now thinking it's the timing chain as well. Thanks for the info and advice. We will get to the chain this week and replace if necessary. Front of the engine comes off pretty easy. Any advice?

SkiBoy
08-21-2011, 04:34 PM
Carb is no longer leaking air. It settled down the idle issue a bit. I advanced the timing and the knock came back. We are now thinking it's the timing chain as well. Thanks for the info and advice. We will get to the chain this week and replace if necessary. Front of the engine comes off pretty easy. Any advice?

Found another arc in one of the plug wires. New wires will be here Wednesday or Thursday. Hope that will help the problems.

mmandley
08-21-2011, 07:43 PM
Glad your starting to find smaller issues that might help prolong your rebuild till winter. =)

SkiBoy
08-22-2011, 01:24 PM
I'll let you know what happens next. Thanks for all the help so far.

I looked at a timing chain today on a similar boat engine that threw a rod. He opted for a new engine instead of a rebuild. Simple but heavy duty chain. Two sprockets no tension arm. If the new plug wires don't help, we'll take a look at the chain later this week.

WaterBullDawg1980
08-23-2011, 05:44 PM
definitely keep us updated. Interesting to follow and learn.

SkiBoy
08-26-2011, 03:31 PM
New plug wires are on. I found a set of Indmar on E-Bay for $35. No change in how it runs, slight knock still there on start up. Mechanic will come out on Monday to ride and listen while I ski. Next step is to check and see if the timing chain was stretched. Will let everyone know what happens next.

Thanks

SkiBoy
08-30-2011, 06:34 PM
Reread all the posts here and all thats comming to mind is if your still having idle flutuations you got a air leak someplace. Its effecting the vacume side and this is making you run lean. Maybe try running the carb rich for a day and see if that compensates for the lean idle. I used to run my 79 Trans Am real lean at idle to get that shaker hood shaking hard for stop light intimidation but i have the jets in the carb over sized to run rich so when i punched it she drank fuel like i do beer LOL.

If you run it rich and the knock is still there im also concerned with your timming and wondeirng if the timming chain hasnt stretched and its trowing everything off. Not much left on the outside to mess with its looking more and more like a winter rebuild my friend.

I turned the fuel up on the primary. (on both sides,one full turn) Had more power and held speed better. (slighter knock at take off ) Mechanic does not think the chain has stretched, but we may have to check. Why do you think a complete rebuild is in order?

Mikes
08-30-2011, 09:00 PM
At 800 hrs. WITH proper maintainence it should not need a complete rebuild. For example, my wife's last Yukon at 160,000 miles had 3200 hours on it.

maxpower220
08-30-2011, 09:46 PM
IMO, I doubt that you stretched a timing chain, but it is possible. Go through and check all of your battery cables and wires. Make sure that you have a good ground and there is no corrosion. Since you were arcing from plug wires and replaced them, make sure that your plugs aren't crack from checking them. That's all I can think of for now.

mmandley
08-30-2011, 09:46 PM
I turned the fuel up on the primary. (on both sides,one full turn) Had more power and held speed better. (slighter knock at take off ) Mechanic does not think the chain has stretched, but we may have to check. Why do you think a complete rebuild is in order?

OK you can only compare cars to boats to a certain extent, First Cars have a ton of electronics and sensors to test and readjust everything to keep it all balanced. Cars arnt considered as working in an extream environment. Cars dont run at 3K RPM on a regular basis for any extended amount of time.

Boats have 1 gear, are plowing weight threw the water, sometimes almost 2xs there weight, boats have 1 gear, boats operate at 2 to 4K RPM constantly. Boats dont have half the sensors or the computers to manage everything and keep the engine dialed in to a fine margine for error. Boats tend to only get used half the year then sit for the other half, this is very hard on mechanical parts. They are designed to be used on a very regular basis.

With 800hrs i wouldnt expect you to need a rebuild but then again lots of engines arnt built to the exact same spec and have flaws.

My other reason is if you have checked all the fuel curves, spark curves, ran a computer diagnaostic on the engine, adjusted timing, spark, fuel, and made sure the fuel is of high qulaity, replaced all the filters, cap, rotor, wires, plugs and you still have this problem. Then something is still wrong and at this point you have replaced everything on the outside of the engine that can cause this issue. Then this is why i beleave a rebuilt might be in order.

At any point you remove parts like the heads to inspect you might as rebuild the engine. Whether its a top end, bottom end, or complete. You dont just remove a head replace a part and put it back together. This is the time you be smart about it and plane it, deck it, improve on it while its apart.

SkiBoy
08-31-2011, 01:03 PM
I have not run a computer diagnostic yet. I have a CAR MD unit, but there is no where to plug it in. (that I can see) The computer is under the steering wheel and dash.

The boat is idling much better after increasing the fuel mixture. I adjusted the idle after the fuel screws. I'll try to advance the timing a bit and see what happens.


Thanks.

mmandley
08-31-2011, 04:16 PM
Sounds good Ski, im not trying to push you to a engine rebuild at all. Im really not lol. I hate to think my boat would need a rebuild at 800 hours. I was only saying when everything else outside the engine has been tested or replaced theres really no other option is all.

SkiBoy
08-31-2011, 06:27 PM
Sounds good Ski, im not trying to push you to a engine rebuild at all. Im really not lol. I hate to think my boat would need a rebuild at 800 hours. I was only saying when everything else outside the engine has been tested or replaced theres really no other option is all.

I understand. I hope to get a compression test done and then a leak down on any cylinders that are weak. I too think a rebuild is in order. Just hoping to get through the last 60 days or so of skiing I have planned. Maybe.....Maybe not.

I put a new set of plugs in today and she is idling better, but still runs a bit rough. I advanced the timing a smidgen and the knock came back. Sigh. What could be causing the lean condition? I checked all around the carb and manifold for leaks. No change in idle when I sprayed carb cleaner.

Ughhh

SkiBoy
10-29-2011, 11:54 AM
Just wondering if anyone thinks it could be a leaking head gasket between cylinders? No oil is leaking from outside gaskets.

Idle was fine for the last few weeks. No change or jump in idle speed after a run around the lake. It's not using oil, and when I changed the oil and filters for storage, there was nothing in the filters and the oil was normal.

Boat was still idling rough, but there was no change in idle speed.

Boat is up for the winter, but accessable for leak down testing, etc.


Thanks

keehr22
10-30-2011, 05:07 AM
Hate to say it, but sounds exactly like what I ran into with our '01 American Skier. 5.7 Vortec engine, started knocking after a long day on the lake, same symptoms you've mentioned. Turns out, after a failed leak down test, we found a head gasket leak between the two middle cylinders on one side (cylinders 3 and 5).

Now for the bad part. Had we shut it down immediately and found the issue initially, it would have been a somewhat cheap fix. But, we continued to troubleshoot, running it under load, and that caused torching of the two mating surfaces, instead of just blown gasket material. With the extent of torching on the block side surface we were faced with a full engine replacement.

I would have a leak down test performed, starting with the middle two cylinders on each side (3 and 5, 4 and 6).

SkiBoy
10-30-2011, 07:32 PM
Thanks. I have gotten the same response on another forum. I hope it isn't ruined, but it may be. I used the boat for two months after the initial spark knock. We turned down the timing until the knock disappeared. The boat had no power and would run about 34 -35mph. (no knock) I turned up the timing a bit to improve speed up to 36 and this created just a bit of knock at start up, but not after. Even during shortline skiing at 32-35 off, there was no knock except at take off. Odd. The knock was slight, but there. If I pulled up a skier on two skies there was no noise at all.

I'll do the leak down and let you know what happens. If I get leaks, I'll pull the motor apart and see what damage there is.

SkiBoy
05-09-2012, 02:31 PM
Had two new mechanics listen to the boat yesterday with timing advanced to factory settings. Both said bad camshaft.
They will tear down top half and see what else needs to be done. I'll report back after it's over. Thanks for all the replies and help.

bergermaister
05-09-2012, 04:02 PM
Although it could be messy, you might consider pulling valve covers, keep rags stuffed on the edges, and run the engine at idle and see if you have flat lobes on the cam by the movement of the rockers. This would only be if you have some REALLY flat lobes but it may be noticeable. I'd consider that last step before pulling the top end of the engine apart.

Went through this with an old chevy pickup - a small block chevy is a small block chevy though.

maxpower220
05-09-2012, 04:55 PM
You should get the mechanics to explain how a cam shaft will knock sometimes, but not knock when the timing is changed. I'm no expert, but I have torn down a few small block chevy engines. I can't say that I have heard of a mechanical failure of a cam that will make (or not make) noise with a timing change. I am open to learn, but I would want an explanation before an engine tear down. However, I think you will be tearing down the engine anyway. I would just want to be on the right track first.

z28ke
05-09-2012, 06:24 PM
I'm with maxpower on this, my old mastercraft 351 wore a lobe and the rocker clack was constant, just louder under load. Timing won't affect the noise.

harmsway
05-09-2012, 09:23 PM
A partially warn cam lobe could be compensated by the hydrolic lifter, which would allow the pushrod to apply enough pressure to the rocker and there would be no noise. If it is the intake lobe that is warn it would not allow the intake valve to open to its full potential, intern not allowing enough fuel into the cylinder during the compression stoke. Then when the engine fired it would cause that cylinder to run lean. This would cause a spark knock under a load. As the lobe wore further you would develope a tapping noise and possibily a back-fire.

SkiBoy
05-11-2012, 12:34 PM
Small crack in the block was found between 4and 6 on the right side, as well as a missing piece of the head gasket. No scorching of the cylinder walls from leaking gasses but the damage is done. Retarding the timing helped a bit, but not sure if there was anything I could have done differently while trying to diagnose the problem.

I'll post a photo when I can. Rebuild is under way and should be done in 10 days or so. They build racing engines and have a machine shop on site for decking and planing of surfaces. They also had a block on site also, as well as a few marine engines.

Sad to see this engine torn down. It ran really well for 12 years and only had 800 hours on it.

Looks like I'll be keeping this boat for a few more years. I'll get some interior work done and get it looking like new for the upcoming season.

Thanks

maxpower220
05-11-2012, 07:02 PM
That makes much more sense. Sorry for the issues, but those things happen. I once had an impeller go out while I was skiing and the driver didn't realize it. So, the engine overheated and warped the head and blew the gasket. I saw the gasket when I tore the engine apart, so I replaced it and to my dismay it overheated. That is when I realized the head was warp. So, I got good and fast at engine tear down on the heads. I think that motor has about 900-950 hours on it.