Absolutely frustrated with this Mercruiser engine

Hoplite808 said:
...I know the data from the ECM says it’s advancing but I can’t test that with it running due to it needing to be in maintenance mode which negates the electronic advance in order for the timing light to give me a reading from the crank.
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I don't understand that part. Why does it need to be in maintenance mode? Why can't you just hook up the timing light and point it at the balancer and then run the engine from idle up to ~3,000 RPM? Even if you used an "old school" timing light without an advance feature you might have to make some marks on the balancer if there's not a good timing indicator on the block (that would show a variety of timing positions like the old engines had).
 
For the umpteenth time mechanical soundness isn't confirmed until you verify the camshaft and the valve timing. A place you haven't been.

Original owner has no insight on what might be the problem? I'd bet he knows the answer.
 
rustybronco said:
17.22 would indicate an elevation of around 5,000ft. It looks like the manifold gauge connected shows around 15 inHg ...
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Not sure I understand what you're saying here. Baro still showed 30.51, which would be normal at near sea level. 17.22 was the MAP reading at idle, which is "in the ballpark". If the manifold gauge showed 15, then I'd say they're reasonably in sync.
 
@km1125 It’s a thing with the MEFI 1 and electronic ignition setup. I only have a very basic timing light and without it in maintenance mode the spark appears all over the place. You just can’t get a reading. This is normal for this engine setup per the SELOC repair manual. I can only obtain an accurate timing reading at 1500 RPM in maintenance mode to set it to the correct mark, which if memory serves is 8 or 10 BTC. I didn’t create the system or procedure and I’d like to slap the engineer who did but that’s what it is.

@scoflaw the previous owner is deceased. I bought the boat from his widow who had been keeping it but not maintaining it properly for a while after his death. She finally decided to sell it because she realized that she couldn’t take care of it and let it go for what I thought at the time was a fair price based off of my own looking at it and paying a surveyor to double check it.
 
Hoplite808 said:
@km1125 It’s a thing with the MEFI 1 and electronic ignition setup. I only have a very basic timing light and without it in maintenance mode the spark appears all over the place. You just can’t get a reading. This is normal for this engine setup per the SELOC repair manual. I can only obtain an accurate timing reading at 1500 RPM in maintenance mode to set it to the correct mark, which if memory serves is 8 or 10 BTC. I didn’t create the system or procedure and I’d like to slap the engineer who did but that’s what it is.
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If you're trying to SET the timing, then you use that procedure but you don't have to put it in maintenance mode just to CHECK the timing. At any time you should be able to MEASURE the timing and compare it with what the Fox Marine data is showing what the ECU thinks the timing is. It is a bit easier to do it with a timing light that has an "advance" knob, but not impossible to do it with a very basic timing light. All you need to do is mark the crank damper or timing cover with marks that indicate "degrees before top dead center". (on shaft-drive engines, you could also make those marks on the flywheel end, but I'm not so sure you can do that with a stern drive).

Making sure the timing is set reasonably and that it is increasing as RPMs increase is an important troubleshooting step for "loss of power" situations. You also want to make sure there are not any "knock retard" numbers indicated on the Fox Marine display.

You can actually also set the timing just by adjusting the current measured timing to what the ECU reads on the Fox Marine display, instead of forcing it into maintenance mode. Maintenance mode is easier though.
 
@hoplite : i would recommend to check the ignition and if no result the culprit sits somewhere in the valvetrain occouring only at load . Very unprobably but not to fully exclude a bearing in the drive locking up when the prop generates thrust. But i do not think so .
 
C’mon guys….. one of you has to be good at throwing darts….. right now you are all missing the board

Pull it….. replace it ….. go boating ——— bullseye :)
 
techmitch said:
May I'm missing something here so please excuse me if so.
14.7 Hg or Bar is not the same as 14.7 psi.
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That's right, but it all depends on what you're trying to measure. If we're talking about compression pressure then you likely wouldn't be measuring it in Hg (or, really inHg). You might do it in Bar, but most compression testers aren't indicated in Bar, they're typically indicated in PSI.

But lets say you did have a gauge that measured in Bar. If it was gauge pressure, it would read 0 Bar at atmospheric. If you compressed atmospheric 8.6 times inside a cylinder you'd have 8.6 Bar, but that gauge would indicate only 7.6 Bar. Same with PSI. If you had a gauge that read 0 PSI at atmospheric and then compressed that air inside a cylinder 8.6 times, you've have 126PSI inside the cylinder, but that same gauge would only read about 112 PSI.
 
km1125 said:
If you're trying to SET the timing, then you use that procedure but you don't have to put it in maintenance mode just to CHECK the timing. At any time you should be able to MEASURE the timing and compare it with what the Fox Marine data is showing what the ECU thinks the timing is. It is a bit easier to do it with a timing light that has an "advance" knob, but not impossible to do it with a very basic timing light. All you need to do is mark the crank damper or timing cover with marks that indicate "degrees before top dead center". (on shaft-drive engines, you could also make those marks on the flywheel end, but I'm not so sure you can do that with a stern drive).

Making sure the timing is set reasonably and that it is increasing as RPMs increase is an important troubleshooting step for "loss of power" situations. You also want to make sure there are not any "knock retard" numbers indicated on the Fox Marine display.

You can actually also set the timing just by adjusting the current measured timing to what the ECU reads on the Fox Marine display, instead of forcing it into maintenance mode. Maintenance mode is easier though.
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With how they designed this set up the only way to get a reading of the timing with a timing light is to put it into maintenance mode. Otherwise the timing light flashes will not make any sense with the mark on the crank. It’s an over complicated design that was made early on when Mercruiser was adding electronic ignition systems and fuel injectors and they moved on from the design apparently very quickly. I don’t like it, but it is what it is.
 
km1125 said:
But lets say you did have a gauge that measured in Bar. If it was gauge pressure, it would read 0 Bar at atmospheric. If you compressed atmospheric 8.6 times inside a cylinder you'd have 8.6 Bar, but that gauge would indicate only 7.6 Bar. Same with PSI. If you had a gauge that read 0 PSI at atmospheric and then compressed that air inside a cylinder 8.6 times, you've have 126PSI inside the cylinder, but that same gauge would only read about 112 PSI.
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I do not think so since you have inside the uncompressed cylinder initially also not absolute zero but athmospheric pressure . If the gauge dials zero when you plug it in the cylinder hole it will measure simply the difference between uncompressed and compressed pressure inside this cylinder . So basicly our 8.6 ratio plus pressure from heat . The final compression pressure is dependent on the ratio as well engine geometry like cylinder bore , combustion chamber and piston design ( how much heat is instantly absorbed )

Its also important to realize compression ratio alone does not give a mathematical result of the actual compression pressure .
 
aerobat77 said:
I do not think so since you have inside the uncompressed cylinder initially also not absolute zero but athmospheric pressure . If the gauge dials zero when you plug it in the cylinder hole it will measure simply the difference between uncompressed and compressed pressure inside this cylinder . So basicly our 8.6 ratio plus pressure from heat . The final compression pressure is dependent on the ratio as well engine geometry like cylinder bore , combustion chamber and piston design ( how much heat is instantly absorbed )

Its also important to realize compression ratio alone does not give a mathematical result of the actual compression pressure .
Click to expand...

A compression test should be performed on a fully (as best as possible) warmed up engine. Cylinder and piston temperature are important as is cranking speed so a good battery, good starter, all of the plugs out and wide open throttle are important. Also, disabling injector firing is essential
 
@Hoplite808 - when you set up the valve train with the adjustable rockers how exactly did you adjust the preload on the lifters and how did you index the camshaft for those adjustments?

I ask because if the preload was set too deep into the lifter there is a possibility that the lifter will pump up and float valves at X RPM.
 
ttmott said:
@Hoplite808 - when you set up the valve train with the adjustable rockers how exactly did you adjust the preload on the lifters and how did you index the camshaft for those adjustments?

I ask because if the preload was set too deep into the lifter there is a possibility that the lifter will pump up and float valves at X RPM.
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I just followed the normal procedure for a big block Chevy. Set it to TDC on cylinder 1 and take the slack out and another half turn. Rotate engine and repeat until everything is set essentially. Then start engine and back off the rocker nut till clacking is heard and then bring it back in till the valves run quiet. That’s the adjustment in a nutshell.
 
Hoplite808 said:
I just followed the normal procedure for a big block Chevy. Set it to TDC on cylinder 1 and take the slack out and another half turn. Rotate engine and repeat until everything is set essentially. Then start engine and back off the rocker nut till clacking is heard and then bring it back in till the valves run quiet. That’s the adjustment in a nutshell.
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The second part on adjusting when engine is running will not set the preload correctly. Hydraulic lifters must be set with that 1/2 turn after slack is removed on the base circle of the cam - no further adjustment is needed. There is a possibility that one or more of the valves may be floating if you did the running adjustment.
 
I can only speak of how things were with non positive stop stud mounted adjustable hydraulic lifters years ago. The procedure was, with the engine warm and running, and after initial adjustment (both valves closed TDC) was to back off on each rocker arm adjusting nut until the rocker arm clattered, tighten until the noise just stopped and added one additional full turn one fourth turn per time (90 degrees) allowing the engine to stabilize between each 90 degree movement. The problem on some high mileage engines was when varnished plungers didn't allow for the full 360 degree adjustment so 1/2 to 3/4 turn was acceptable (180~270). The reason for the one additional turn was to center the inner plunger in the middle of it's range of travel.

Positive stop stud mounted rocker arms could be adjusted for various engine machining operations that changed the position of the inner plunger by using under or oversize push rods.

They also make pads that clip onto the end of the rocker arm where the push rod oiling hole is located in order to reduce oil "lubricating" the engine compartment.
 
This statement bothers me.

I only have a very basic timing light and without it in maintenance mode the spark appears all over the place. You just can’t get a reading.
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I'm not saying that it isn't in the manual, it just sounds contradictory to everything I've ever known or seen. Why in the heck would they ever throw spark at varied crankshaft positions when the engine rpm is stable? A few degrees I can understand when wear is involved.

I have seen a procedure on how to set base timing with or without the Diagnostic Code Tool, or MerCruiser Special Timing Tool but I still don't understand the reason for the instability. Don't know the sensors and controls used and what sort of feedback loop is used on this engine. Guess it's time for me to read up on it.
 
https://www.baylinerownersclub.org/...54-low-total-spark-advance-at-wot-gctid637982

1... The knock sensor detects Detonation, and apparently causes the ECM to cut back on the advance (further delay) until resolved.

2.... In post # 6 you mention that you checked the BASE advance. How are you checking or setting BASE advance if not going into BASE mode?

Re; #1....... I spoke with a Merc Tech some time back, and this topic came up.

He mentioned that he once had a similar issue and that it turned out be a main drive shaft vibration or clicking that triggering an overly sensitive knock sensor.
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I believe the knock sensor retarding (delaying) the spark timing has been brought up before.

Also brought up it the linked article is the possibility of a slipped outer ring on the dampener. (If equipped.)

MORE...
Got home and opened laptop and studied the recording from the last four outings. MAP sensor looked to be fine. Injector pulse was 11-12 msec. Then it jumped out to me, the TPS in all four recordings dropped from 93-100% to 65.3% (voltage was 4.4-4.6 then dropped to 3.06) and stayed there, RPMs stayed at 37-3800 the whole time. During these tests I never throttled back for more than a couple of seconds while testing throttle response.
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You could measure the voltage on the "return" (signal) output of the TPS in lew of the scan? tool.

OP said:
So far I’ve replaced the cylinder heads, exhaust manifolds, the spark plugs, spark plug wires, cap, rotor, distributor, ignition coil, ignition module, air temp sensor, MAP sensor, IAC, throttle position sensor, mechanical fuel pump, the electric pump in the vapor separator tank, the alternator, raw water impeller and housing, the heat exchangers, thermostat and housing, engine temp sender, oil pressure sender, the entire outdrive, and repaired or replaced wiring. I have quadruple checked the timing and fuel pressure. All is set exactly as it should. Fuel in the tank has been flushed and replaced with new. Oil is fresh and pressure is good. Engine coolant temperature is fine. Compression in all 8 cylinders is 120 psi and testing for spark at all 8 cylinders showed no problems.
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Just things to think about.
 
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