Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

[damo79]

@muc please see attached recent Diacom test run with new battery.
Old one wast tested and it was time to replace it. Capacity was still ok but cranking current only 480A. New one is 850A
Didn't notice any change in performance, still the same

 

[muc]

This wasn't the REC file I was hoping for.

Here is what I see.

Voltage still too low. this might explain the numbers I'm seeing and the many sensor spikes at unusual times.

Sea water pressure too low and has some of those spikes. Maybe this affecting the WOT? I'm not sure.

Fuel trims very high (very close to setting fault) at strange times and have a wider difference between port and stbd that what I'm used to seeing.
.
phi (equivalency in Diacom) both target and actual are much higher then normal. Also unusual spikes. From the manual "The difference between phi and DesiredPhi can indicate things such as fuel restriction, fuel quality, high fuel rail pressure, fuel injector failures"

It appears trim sensor is inop or you're not using the trim. Are you using trim? This makes it hard for me, I'm not there so I need to look at demand, demand linear, TPS, etc. to try and figure out what is happening with the steering wheel and waves. Can you tell me a little about this run. I can see you going in and out of gear (this is hard for me to interrupt because Diacom calls these switches by different names) then Merc does. Also many times you back off on the throttle before increasing it to get to the next RPM range. I'm not there so maybe water conditions?

When I look at the (little over a minute) WOT part of the file. I see you have the throttle 100%, the PCM is commanding 100%, but for some reason the TPS is slowly closing to 65%. I can see no reason for this to be happening anywhere in the REC file. It's very normal to see this at demand linear less then 100% because ACS is trying to keep a constant RPM, but not at WOT.

I have some questions.
Have you replaced O2 sensors? If so, did you use OEM?
Have you dumped the fuel filter into a clear and clean glass to inspect? Have you replaced the filter element?
Have you tried running the engine on a different fuel tank filled with the best gas you can buy?
Do you have a picture of the stickers on the PCM?

Next time you do another Diacom run, you should trim up far enough to blow out the prop at WOT. It might help to see what happens when you hit the rev limiter. Don't worry about over reving the engine, the PCM is way to smart to let anything bad happen.

So to sum up, I can see why you can't get over 4500, I just don't know why.

 

[muc]

Seems strange that Bayliner states that boat was sold with engine currently installed and you found out that thia engine was warranty return sold on Merc auction in 2018.

Yes I have never seen this before. Maybe a EU thing? Engine build date 2016 sold in 2018. I'm not sure about it being a warranty return, just that the engine only was registered by the warranty dept.

 

[damo79]

This wasn't the REC file I was hoping for.

Here is what I see.

Voltage still too low. this might explain the numbers I'm seeing and the many sensor spikes at unusual times.

Sea water pressure too low and has some of those spikes. Maybe this affecting the WOT? I'm not sure.

Fuel trims very high (very close to setting fault) at strange times and have a wider difference between port and stbd that what I'm used to seeing.
.
phi (equivalency in Diacom) both target and actual are much higher then normal. Also unusual spikes. From the manual "The difference between phi and DesiredPhi can indicate things such as fuel restriction, fuel quality, high fuel rail pressure, fuel injector failures"

It appears trim sensor is inop or you're not using the trim. Are you using trim? This makes it hard for me, I'm not there so I need to look at demand, demand linear, TPS, etc. to try and figure out what is happening with the steering wheel and waves. Can you tell me a little about this run. I can see you going in and out of gear (this is hard for me to interrupt because Diacom calls these switches by different names) then Merc does. Also many times you back off on the throttle before increasing it to get to the next RPM range. I'm not there so maybe water conditions?

When I look at the (little over a minute) WOT part of the file. I see you have the throttle 100%, the PCM is commanding 100%, but for some reason the TPS is slowly closing to 65%. I can see no reason for this to be happening anywhere in the REC file. It's very normal to see this at demand linear less then 100% because ACS is trying to keep a constant RPM, but not at WOT.

I have some questions.
Have you replaced O2 sensors? If so, did you use OEM?
Have you dumped the fuel filter into a clear and clean glass to inspect? Have you replaced the filter element?
Have you tried running the engine on a different fuel tank filled with the best gas you can buy?
Do you have a picture of the stickers on the PCM?

Next time you do another Diacom run, you should trim up far enough to blow out the prop at WOT. It might help to see what happens when you hit the rev limiter. Don't worry about over reving the engine, the PCM is way to smart to let anything bad happen.

So to sum up, I can see why you can't get over 4500, I just don't know why.

System voltage still drops to 10.2V. Checked @tpenfield files and both his V8 engines do the same while cranking. Maybe that's normal.

Sea water pressue been an issue from the time it suddenly dropped and stayed like that (maybe 2 weeks). I will check that this week. Maybe its just he sensor - water temp stays within the range.

What do you mean by very high fuel trims? They stay within 2-5% while on steady rpm and spikes are during acceleration and slowing down from WOT is the biggest spike -14% but only few seconds.
I agree that port is always -2..4% and stbd +2...4% not sure what sould it be.
Phi - did you mean Equiv Ratio Target?

I use the trim only to the point when I hear prop ventilating and then back of a little. TBH this boat doesn't need much triming that's why you dont see much trim movement.

About the run - first few part up to 3000rpm I was hitting small vawes going downwind. Also trimed down to stop boat pounding. After that when rpm was 3400 and above it was calm and the moments you see me slowing down before going up to next rpm level I was taking turns to try keep the boat in sheltered water.

Without trim at WOT max was 4350rpm and when I trimmed up a little and had a feeling that I only gained rpm from 4350 to 4500 but not speed maybe that's why TPS went down.

 

[damo79]

O2 sensor was replaced with new one. Before I got Diacom, the engine was checked by a marine tech and the only think he told me was that o2 needed to be repleced, because reading stays at the same level all the time.

Little backstory about Bosch sensor. The original one was BOSCH 0258017 244. Its was imposible to buy this specific one - discontinued according to Bosch or what I suspect reserved for Merc, Volvo Penta and John Deere. The OEM Merc was not available in Poland and delivery time was 2-3 weeks. So I contacted Bosch and they recommended 0258017 025. According to and email i received from Bosch , it is the same sensor just with different cable lenght.

I never run the boat from separated tank. I used few tanks of fuel this season and didnt notice any improvement. Fuel filter was replaced before season.

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