Absolutely frustrated with this Mercruiser engine

aerobat77 said:
Ok , it revs up to 4500 but when you ( of course do it just for a split of a second ) in neutral slam the throttle full down , does it respond "aggressive" and "explosive" ?

I,m asking to know if you think the injectors give full fuel spray in this scenario .

This is a bravo drive ? Does your boat has a shift position sensor ?
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When the throttle is pushed hard under load it will aggressively accelerate up until about 2000 RPMs. Then it just stops accelerating. It has the bravo 3 drive with the counter rotating props.
 
I’ve been reading all of this and I do believe you have an engine issue (my wild guess is injectors but internet troubleshooting is hard) but I’m very curious…..is the boat anywhere near getting on plane at 2000rpm?

Im guessing it’s not but I would be very interested to see what happens if you can get it up on plane if the engine accelerates. There’s a very remote chance your issue isn’t even engine related.

The other thing to do, mentioned earlier, is to run it on all new fuel lines to an external tank. It’s amazing how quickly those old lines constrict. You could see pressure stay high on the gauge but the volume isn’t there to feed the injectors.

Both are unlikely but at this point it were all guessing anyway
 
I’m out of my depth but thought I’d ask the simple question of is it propped correctly? Originally it had a gear ratio 2.00:1 and 26 pitch with WOT RPM of 4600.
 
@unsalted I looked all that up prior to the outdrive replacement. The gearing is correct and the props are original and the correct pitch.

@Strecker25 that’s what I’m leaning towards now but I need to find a reputable source to send them to for testing before I spend too much on new ones.
 
That sounds very odd .

You say the engine responds agressively and powerful up to 2000 and then just 'stops' to go higher ( in gear ) . That indicates the ECM commands full fuel spray and the injectors deliver it - at least up to 2000.

Injectors are not fine below 2000 and faulty above so it seems its NOT injectors .

I,m not sure if your setup has a gear shift sensor which reports to the ECM if the engine is in gear or not - later b3/mpi packages have it for sure . It might be your shift position sensor is bad and the ECM is limiting engine output since it believes yiu are still in neutral .

An argument against it - it would be new if this happens at 2000 and why do fou have hard cold stsrting then .

Can you make an informative video of this all ?

Dirty hull or wrong gearing / prop pitch might result in bad performance but not the way you describe .
 
aerobat77 said:
That sounds very odd .

You say the engine responds agressively and powerful up to 2000 and then just 'stops' to go higher ( in gear ) . That indicates the ECM commands full fuel spray and the injectors deliver it - at least up to 2000.

Injectors are not fine below 2000 and faulty above so it seems its NOT injectors .
.
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The engine management system principally works on demand and load (work) - not specifically RPM, however RPM and load is what sets the fueling constant from a table.
So, if there is no load like simply reving the motor, the fuel demand to spin the engine is very little so the engine management system sets the duty cycle on the injectors very low and very little fuel flows to rev the engine. Conversely, in the water with the propeller pushing the boat forward the demand and load is higher. The engine management system says we need more power and sets the injector duty cycle much higher delivering more fuel.
Duty Cycle is simply the ratio of time the injector is Closed over the time Open (Closed/Open) expressed as a percentage; fuel injectors are either open or closed, nothing in between. If the injectors are restricted or can't accommodate higher duty cycles or can't fully open and close, then definitely they will freely spin the engine but not support an engine that has to deliver torque.

Here is another thing regarding looking at the spark plugs - Faulty fuel injectors can confuse a diagnosis to determine rich or lean conditions by looking at spark plugs. If, for example, the fuel injector is malfunctioning and dripping or leaking fuel the spark plug can look wet or carbon fouled as if the engine or that cylinder is running rich which in fact the fuel is simply not being correctly sprayed and actually a lean condition is present. This is exactly why properly tested and calibrated injectors are so critical in setting up a system or in the case of @Hoplite808 so critical for his Mercury ECM to control the engine.
By now he could have had his injectors Fedx'd stateside and clean/tested and back in hand to make a decision to use or buy new rather than trying to find a good service on the islands.....
 
Sounds like my thread, and just as long.....
http://clubsearay.com/index.php?threads/1999-454-mag-mpi-just-quits-videos.101750/
I'll save you the pain of reading the whole thread. Spun crank bearing. Ran great at 2000 rpm. Put on plane, at 3100, and it would fall off. Repeat, and kept falling off, but sooner each time. What happened? The bearing would heat up over 2000 rpm, and expand or slip, causing enough friction to slow the engine, and then, no start after running for a while until it cooled down. Remedy? New block. The bearing wallowed out the block side of the bearing cap past the point of fix or ignore. I'm now a couple of weeks out from starting the "new" engine. Found lots of other issues through the adventure. Hindsight? I should have just run it at 2000 until something really broke, and then repowered with electric. Oops, did I say that out loud?
 
ttmott said:
The engine management system principally works on demand (throttle position) and load (work) - not specifically RPM.
So, if there is no load like simply reving the motor, the fuel demand to spin the engine is very little so the engine management system sets the duty cycle on the injectors very low and very little fuel flows to rev the engine. Conversely, in the water with the propeller pushing the boat forward the demand and load is higher. The engine management system says we need more power and sets the injector duty cycle much higher delivering more fuel.
Duty Cycle is simply the ratio of time the injector is Closed over the time Open (Closed/Open) expressed as a percentage; fuel injectors are either open or closed, nothing in between. If the injectors are restricted or can't accommodate higher duty cycles or can't fully open and close, then definitely they will freely spin the engine but not support an engine that has to deliver torque.

Here is another thing regarding looking at the spark plugs - Faulty fuel injectors can confuse a diagnosis to determine rich or lean conditions by looking at spark plugs. If, for example, the fuel injector is malfunctioning and dripping or leaking fuel the spark plug can look wet or carbon fouled as if the engine or that cylinder is running rich which in fact the fuel is simply not being correctly sprayed and actually a lean condition is present. This is exactly why properly tested and calibrated injectors are so critical in setting up a system or in the case of @Hoplite808 so critical for his Mercury ECM to control the engine.
By now he could have had his injectors Fedx'd stateside and clean/tested and back in hand to make a decision to use or buy new rather than trying to find a good service on the islands.....
Click to expand...
Oh and one other important thing - the engine load is determined by the intake manifold pressure and transmitted to the engine management system through the Manifold Absolute Pressure (MAP) sensor. Some systems determine load through air flow measurement using a Mass Air Flow (MAF) sensor but Mercury uses manifold pressure. As one opens the throttles the manifold vacuum raises towards atmospheric pressure and indicates to the ECM a demand for fuel. Engines under high load have higher manifold pressures (closer to atmospheric pressure). If the MAP sensor was malfunctioning the ECM would send a fault code.
 
ttmott said:
Oh and one other important thing - the engine load is determined by the intake manifold pressure and transmitted to the engine management system through the Manifold Absolute Pressure (MAP) sensor. Some systems determine load through air flow measurement using a Mass Air Flow (MAF) sensor but Mercury uses manifold pressure. As one opens the throttles the manifold vacuum raises towards atmospheric pressure and indicates to the ECM a demand for fuel. Engines under high load have higher manifold pressures (closer to atmospheric pressure). If the MAP sensor was malfunctioning the ECM would send a fault code.
Click to expand...
That was changed in the first volley of parts swapping (post #1). Injectors-injectors-injectors-injectors. Oh, wait; developers-developers-developers-developers.
 
Hoplite, I had never even really thought of the trouble you might have with shipping things on/off the island. But it got me thinking, so I went to FedEx's website and did a quick quote for a small box (should be adequate to ship 8 injectors) to be shipped from PA to HI 2nd day air.

It was $37. I was actually surprised as that sounds very reasonable. Why not do that? There are tons of shops stateside that do this thing every day.
 
The mefi 1 is very dumbed down. Would be nice to look at the MAP value that ecm might not trigger a fault.
Send those injectors to a place that would be able to sell you new if they can't repair them.
 
Just a thought, you could consider a fox-marine engine gateway and get some insight into the ecm. Would run you about $400 but would later be a nice addition to the boat. Here is what it will track and the data is available via Bluetooth and N2K.

Engine RPM is transmitted twice per second while the remaining data is transmitted once per second: Fuel Flow Rate, Coolant Temperature, Alternator/Battery Voltage, Engine Run Hours, Throttle Position (Engine Load), and Active Alarms. Oil Pressure is transmitted with the purchase and installation of the optional Oil Pressure Kit.
 
Like everyone else on this post I am hoping the problem is found soon, and for the least amount of money. I will throw in my two cents worth.

1. Alternator, I think it has been replaced, but worth checking, if the alternator is putting out too much AC voltage then that can cause limited performance when under load. Put DVOM on AC volts and measure at the back of the alternator. Reading should be negligible, may be 0.2 - 0.3 volts max if I remember correctly.
2. The fact that it happens under load leads to the issue of possible voltage drop, on either the positive or negative wiring. When voltage drop does occur it is usually on the ground side (not sure why that is, I think it was invented by the British Auto industry, I am British by the way). Complete voltage drop tests when the engine is under load. Probably best to You Tube voltage drop test if you are not sure how to check. So many engine running problems are caused by poor connections. A bad wire/circuit can test as good when completing a resistance check, but completely fail a voltage drop test when tested under load.
3. I had a poor running condition on my boat back in 2020, not quite the same, but my port engine intermittently would not run past 3100 rpm when under load. (My post is here http://www.clubsearay.com/index.php?threads/engine-ecu-swap-for-diagnostic-purposes.95267/) Even after sending the ECU out to OBD Diagnostics in CA who deemed it to be good I switched the ECU over to the starboard engine and the issue moved to that engine. I purchased a new ECU from ODB Diagnostics and problem solved (I assume they did not see an issue with the ECU as their test rig does not put a true load on the ECU) I know I had the luxury of switching parts as I had two engines, but may be borrow an ECU from a similar boat?
 
Hoplite808 said:
@Scott215 I appreciate all the help and knowledge this forum is sharing with me. As the title of this thread says I am frustrated by this engine. For those who are befuddled by the lack of qualified mechanics and other services I mention. Hawaii has rated dead last by the NMMA out of all 50 states in boating for decades. Kansas has better boating industry infrastructure than Hawaii. For some reason Hawaii likes to keep the local government very liberal and even more incompetent.
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Yeah - I was was extremely frustrated and basically threw away $1.5k ordering a non returnable ECM, when it turned out to be a $75 crankshaft sensor. Didn’t throw any codes but stalled the motor at higher rpm’s under load - not in neutral. I have a spare ECM now tho ;)
 
I'm going to say this but most will not like it is my guess. Put this POS engine in the dumpster and get a rebuilt or running takeout 496mag, put it in and go boating. I would imagine at this point this whole boat thing really sucks and is no fun.
Replace and forget.
 
kevin27 said:
I'm going to say this but most will not like it is my guess. Put this POS engine in the dumpster and get a rebuilt or running takeout 496mag, put it in and go boating. I would imagine at this point this whole boat thing really sucks and is no fun.
Replace and forget.
Click to expand...

If there was a junkyard I could pick from and score a new/used engine for less than $10,000 for I’d have done that a while ago. Alas such a place does not exist near me and a new crate motor would be the only option. I know the issue does not have anything to do with the mechanics of the block anyways. This is some sort of issue with either the fuel system or the ignition system I just can’t isolate what the problem is.
 
Hopelite can you have somebody watch the fuel pressure gauge or the fuel pressure at wide open throttle just to see if it drops it's a shot in the dark but at this point I would take anything
 
Does it just like at 2000 RPMs does it just like hit the ceiling right there and that's it it doesn't run rough it doesn't do anything other than just stop at 2000 cuz that kind of sounds like an electrical issue if it's only revenue to 2000 and that's its ceiling it sounds like something's not communicating with something
 
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