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

[muc]

I tried to answer all your questions and give you my insight. If I missed anything let me know and I'll try to help.

 

[muc]

I can't edit post #116
When I said.
"Any drop above 0.5v is bad. So 0.4 while at full charging is the only good number you have!"
I should have been clearer. during cranking the voltage in the battery will drop more then 0.5v. But this is in the battery, not in the wires and connections. Also the starter itself will use about 1.5-2 volts.
Either way you got some electric issues.

 

[nola mike]

This is an awesome thread, thanks guys

 

[damo79]

I haven't had much time today to spend on this, but I did want to cover the most important part ---- electrical system.

There are a lot of checks, calculations and choosing of all the tables that happen during starting, so correct power is critical. This is why I recommend that during starting. Turn the key to ON and wait a couple of seconds and then turn to START.

Open Diacom
Load the REC file with the cranking event.
Top of screen select Graph
Left side of screen click the top button
Now chose
batt volts
engine speed
system volts and click ok
Here is what I see.

system @12.5v batt @12.0v so we have a .5v drop between these 2 before cranking.
Here's where I have to Guess, Diacom doesn't always use the same names as Mercury does.
My guess, batt is probably looking at the Clean Power and system is probably looking at the internal voltage regulator in the PCM. system will be the more important of the two, because this is what the PCMs calculations is based on.

Now scroll to where the RPMs start going up, see what happens to the system and batt? system now @ 8.46v and batt at 10.06v so we now have a 1.6v drop between these two. And a WAY to low voltage!

Now scroll some more to where RPMs reach max. We now see system @ 14.7 and batt @ 14.3 = .4v

Now lets do some math and look a little deeper.
The voltage drop during cranking is system 4.04 v and batt 1.94v. This is a 2.1v difference between them during cranking.

Any drop above 0.5v is bad. So 0.4 while at full charging is the only good number you have!

This leads me to think you have a bad battery and some excessive resistance in the wiring.

Troubleshooting,
Start with physical inspection. At the battery remove all negative connections and inspect them. Note that 4 connections are all that's allowed. They should be stacked with the wire that uses the most power is closest to the battery and so on. Put tie strap thru all the rings so the wires all stay together and put them to the side.
Now the positive post, same deal but this time there will be an inline fuse in the clean power wire, pull it out and inspect it to.
Now it gets a little (or a lot - depends on the boat) harder. Follow the pos+neg big cables and clean power ALL the way to their ends. You are looking for any splices, connectors and terminations, like the battery switch.
disassemble and inspect all of them.
A good marine tech will skip this and instead do a voltage drop test on these 4 wires, but I have seen soo many junior techs screw this up, only attempt if your very confident in your electrical skills.
Now with everything reassembled and install a "known good" battery.
I HIGHLY recommend a AGM that is at LEAST 800 CCA, 1000 MCA, 190 Ah.
Retest with Diacom.

Now here is something that you can try next time your on the boat (after you have fixed the electrical problem --- I don't think I can stress this enough! We have identified a problem, this must be corrected before any more troubleshooting!).

After you have done the new complete Diacom REC files.

Check the breather hose that runs from near the flame arrester and make sure you can blow through it. Now find the PCV on the other valve cover and check that it rattles, replace with a new Mercury Marine one if you want. $17.00 here in the states and probable should have been replaced already any way. Now follow that hose to the intake manifold, remove it and plug the nipple in the manifold. Run the boat and see what happens now that you have removed the calibrated air leak and have higher vacuum in the intake.

Once agian thanks for your time and effort- much appreciated.
Battery probably needs replacing but 10-10,5V voltage drop during cranking is acceptable relaying on many internet sources. You mention drop above 0.5V is bad. I will test battery anyway and if its OK then check electrical system.
Does this drop affect issue with low vacuum which in your opinion doesn't exist - sorry but don't think so.

Hoses from rocker cover - checked that while ago. The one going to flame arrester is ok. Other one - had this one disconnected and plugged manifold did full test run no changes. That nipple is also the place where physicall gauge was connected to verify if TMAP in Diacom. Thanks for that advice - thats shows that for a while you considered vacuum being maybe too low.

 

[damo79]

Yes I looked at the chart --- it's the same chart that's in all the manuals since the beginning of time.
I noted that it starts with "most engines" seeing as that chart has been around since points and carbs, I would say you don't fall under that category. I also noted that under low vacuum, first is leaks and 2nd is prop.
I saw earlier that you dropped 2" in pitch with no real change, you should have picked up about 300-400 RPMs -- was that not a red flag?
When they say prop -- what they really mean is to check from one end to the other. That's engine alignment, correct gear ratio and no excess friction the the drive along with correct prop mounting. Along with this is the hull, I don't mean any offence but this is a Bayliner, not known for the strongest hulls. I've seen many boats that sit on bunks or rollers that don't reach the transom. This can cause a hook in the hull and will change propping. This is why we don't guess about correct pitch -- we test in the water.

Yes I watched the fuel pressure tests. But because I used to be a tech, all I see is that you have a gauge that you can't bleed the air out of it (like the manual wants) and it appears to be the cheapest fuel pressure gauge that money can buy. A lot of cheap gauges I've tested read wrong when I check them against a good gauge and it's common that they don't just read a few psi off consistently across the range. I find many that read low at one end of the dial and high at the other end. But when I look at the REC files I don't see the issues I normally expect with low or high pressure, so I gave that a pass. But like I pointed out earlier --- you have an electrical issue that could be critical and the REC files have never had enough good info to be sure. Have you serviced the fuel filter and checked for water? Have you used a temporary fuel tank with good fuel to isolate the boat from the motor. Both are standard troubleshooting and are a really good idea.

Still don't think the vacuum is the ROOT CAUSE. But I'm setting in a comfy chair and I'm not seeing, hearing and feeling what you are, and sometimes that can really matter.

Use the graph function in Diacom to look at O2 control state and RPM / Load state. Are you seeing what I'm seeing? in-out / up-down

Yes I can understand the trials and tribulations of trying to get a good recording. I've had to tow the customer and his wife on a tube with a drift sock at the same time to load the engine and duplicate his complaint. It was a small lake. Yours is a little tougher because of the ASC that's programed in the PCM. Just do the best you can. This takes a lot of time -- don't try to hurry it. garbage in garbage out

We should back up to the beginning.
So I have one more question. What is the complaint that started all this????
We techs are trained on.

Complaint
Cause
Correction

If you keep putting in effort, I will to -- when I have the time.

Vacuum chart is in the manual and it's copy and paste since the beginning of the time just because its simple engine with OHV. That's what I think. It ain't diesel or any modern engine. Guess its there because is applicable. Fuel rail pressure also proves that its not in the range. And yes I thought first time when checked it - cheap gauge should i trust it? But borrowed quality one from mechanic - a friend and it showed the same. Vaccum gauge is a 4USD one of amazon and showes 12.5" while Diacom still below 13".

O2 state on graphs - if you can please explain what's wrong? I see the graph but dont know how to interpret that. Only thing I noticed its stays in closed loop for the whole time when on plane at steady rpm like 3000. Please see on attached screenshots with time stamps. 18:17:43 till 18:19:16. Loop closed, rpm and engine load stedy. It only changes and goes out closed loop during acceleration and deceleration but thats normal. Correct me if I'm wrong.

 

[damo79]

This engine never really gets stabilized enough to look in depth. The fuel and ignition tables are changing to often for me.

It doesn't? See attached screen at 2857rpm. Steady spark advance injectors for as long as rpm stays the same. Do you expect see anything more if its 2min or 5min?

 

[damo79]

I guess that would depend on advanced or retarded. From my understanding this usually happens during a extreme event. Like a hard under water strike or wake jumping. But lets fix the easy stuff before looking at the odd ball stuff.

Yes the manuals can have some issues. Note that Mercury doesn't want us to use the paper manuals anymore. They are out of date the moment they come off the press. The Diag manual for your PCM has been updated 3 times since the first printing to correct errors and update info. And because the last revision was in 2022, it's probably due for anouther. Mercury wants us to download a updated manual anytime we work on a product.

The manual just contains a little theory to jog the memory of a trained tech.

Mercury really tries to force consumers to bring the boat to a dealer that has G3 and a trained tech. G3 will walk the tech through most troubleshooting.
Case in point, the warning horn you had. Most faults have at least 2 things that have to happen before setting a code. In the case of the sea water pressure. The engine must now reach a certain RPM before a horn and that low pressure must last a certain amount of time. Mercury doesn't put that in the manual, you only hear about it in school. And did you see how I said now on the RPM, it wasn't like that in the early days. They changed the program after getting too many nuisance horns. That's another reason they want the engine connected to G3, whenever we connect, G3 checks for the latest program and won't let us go any further until we update it.

Yes there could be many causes for your problem, maybe more then one. That's why we test and identify a problem, correct it and retest.

electrical issue
low sea water pressure
and maybe trim sender

This is why I keep pushing you to focus on the basics. Who knows? Maybe you got a miss stamped prop and it's really 20 1/2" pitch and you really just need to correct the issues we have found and put on a good 19" or maybe 17" prop to get this right.

Your focused on vacuum and as near as I can tell you don't know what gear ratio is on this boat. Or even are sure what the prop pitch is, if you have a prop shop near you, they will throw throw the prop on pitch blocks and confirm it --- for free. Any good tech would have ruled out all this stuff I've talked about before even caring what the MAP is.

I did mention its alpha drive with 1.62 - standard for Bayliner VR5 with this engine.
Now installed standard prop for this setup as I mentioned I get at 3000 and 4000 rpm exactly the same speeds like boat during test in magazine. So prop is what it has stamped same as gear ratio other way speed at the same rpm wont be the same right?
And at 4000rpm fuel consumption is over 50% higher that it should be. Seeing logic of ecm555 only way it can be so high without anomalies on fuel trims and o2 readings is way too low vacuum throughout whole rpm range. But none knows what it should be and even at idle you question what's in manual.
And yes changing prop and WOT not changing a lot was a red flag for me. Is was enough to tell me that prop isn't a problem but something else.
I wont question if stamp on prop or outdrive is correct if my only findings so far is is low vacuum.

 

[muc]

Once agian thanks for your time and effort- much appreciated.
Battery probably needs replacing but 10-10,5V voltage drop during cranking is acceptable relaying on many internet sources. You mention drop above 0.5V is bad. I will test battery anyway and if its OK then check electrical system.
Does this drop affect issue with low vacuum which in your opinion doesn't exist - sorry but don't think so.

Hoses from rocker cover - checked that while ago. The one going to flame arrester is ok. Other one - had this one disconnected and plugged manifold did full test run no changes. That nipple is also the place where physicall gauge was connected to verify if TMAP in Diacom. Thanks for that advice - thats shows that for a while you considered vacuum being maybe too low.

Your System Voltage is dropping to 8.5v during cranking. That is VERY bad according to Mercury Marine. With the PCM112 they want no lower then 11.5v but will accept 11.0v.

I don't care what the internet says, I get my info from Mercury Marine.

Funny story about the internet. Awhile back I helped someone on this forum that was trying to track down what they were 100% certain was a problem with one of the 5v ref circuits, they were seeing 4.8v and everyone was telling them it needed to fixed. After getting their serial number, I was able to tell them 4.8v was exactly what it should be for their particular Volvo engine. A few months later I was reading a post on a different MerCruiser forum. Another 5v ref question. Someone answered that 4.8v was OK and posted a Google link to back up their post. So because Merc never had anything other then 5v on a reference circuit, I clicked on the link. What I saw was an almost word for word repeat of my Volvo post. But the AI had added MerCruiser into it. It seems AI doesn't know that Volvo and MerCruiser can be very different. Just like some people don't know how different a MEFI vs 555 vs PCM112 can be.

Could the drop to 8.5v affect your engine? Yes it could or might not. That's the trouble with this voltage drop with these PCMs. Sometimes it can screw things up, sometimes it doesn't seem to matter. But I will tell you that ANY good tech who does a lot of diag on these engines won't bother until the voltage issue is corrected. We have been burned too many times to take the chance. Batteries are cheap compared to $200 hr diagnostic time.
I'm not trying to be a jerk, just being honest. The next REC file you post, the first thing I will look at is system voltage during a cols start cranking. If it below 11v or not part of the file -- I won't (possibly) waste my time looking at the rest of it.

Please don't remove a calibrated vacuum leak to install a mechanical gauge. The correct way is to T into the reference line to the fuel pressure regulator.

 

[muc]

Vacuum chart is in the manual and it's copy and paste since the beginning of the time just because its simple engine with OHV. That's what I think. It ain't diesel or any modern engine. Guess its there because is applicable. Fuel rail pressure also proves that its not in the range. And yes I thought first time when checked it - cheap gauge should i trust it? But borrowed quality one from mechanic - a friend and it showed the same. Vaccum gauge is a 4USD one of amazon and showes 12.5" while Diacom still below 13".

O2 state on graphs - if you can please explain what's wrong? I see the graph but dont know how to interpret that. Only thing I noticed its stays in closed loop for the whole time when on plane at steady rpm like 3000. Please see on attached screenshots with time stamps. 18:17:43 till 18:19:16. Loop closed, rpm and engine load stedy. It only changes and goes out closed loop during acceleration and deceleration but thats normal. Correct me if I'm wrong.

But it is an modern engine, it doesn't need knock sensors for one thing.

First, there is a possibility those numbers are corrupted.
Second, what is happening at 2500, 3500 etc.
Your complaint seems to be low WOT RPM and excessive fuel usage. We need to see all the RPM range.

 

[Captain of the Double G's]

Once again, when you are done with your thesis, let us know. The rest of us would have replaced it all by now. Stop wasting our time.

 

[muc]

I did mention its alpha drive with 1.62 - standard for Bayliner VR5 with this engine.
Now installed standard prop for this setup as I mentioned I get at 3000 and 4000 rpm exactly the same speeds like boat during test in magazine. So prop is what it has stamped same as gear ratio other way speed at the same rpm wont be the same right?
And at 4000rpm fuel consumption is over 50% higher that it should be. Seeing logic of ecm555 only way it can be so high without anomalies on fuel trims and o2 readings is way too low vacuum throughout whole rpm range. But none knows what it should be and even at idle you question what's in manual.
And yes changing prop and WOT not changing a lot was a red flag for me. Is was enough to tell me that prop isn't a problem but something else.
I wont question if stamp on prop or outdrive is correct if my only findings so far is is low vacuum.

Have you ever been part of a boat test for a magazine? I have, and I sure wouldn't use what they published as a substitute for actual testing.
The people who do these are trying to sell boat --- plain and simple. I've read the article (that's how I found out it takes 3-4 months from the test to published) about the test I was part of. They "bend" the numbers to make things look a "little" better.

I'll just be up front with you. I'm not here because I don't know how to fix this boat. I spent over 30 years as the guy people like you brought the boat to when they couldn't fix it themselves. You are here because you can't fix it yourself.

Your troubleshooting skills are weak.
Your reasoning seems flawed to me.
The testing you have done so far is incomplete.
The opinions you have are based some things you read on the internet --- but only when they agreed with your preconceived ideas.

"Does this drop affect issue with low vacuum which in your opinion doesn't exist - sorry but don't think so."
I don't care what you think, I don't care about a 555 table you found.
I work with facts not speculation.

Low vacuum is only a symptom, not a cause. And yes at this point I don't believe you have low vacuum.

I don't understand why you want to argue with the advise I'm trying to give you. If you want me to, I'll stop posting.

But, I will still try my best to help you.
Fix the voltage issue.
Fix the sea water pressure problem and while you're doing that, if you pull the drive -- count how many times the prop shaft spins when you turn the drive shaft 10 complete revolutions. Or if your just dropping the lower, buy a new o-ring for the top cap and count the teeth.
Try to get a good REC file.

 

[muc]

Once again, when you are done with your thesis, let us know. The rest of us would have replaced it all by now. Stop wasting our time.

I don't see this as a waste of time. I look at it as a learning experience.
Hopefully people who read this thread will see the importance of complete and correct troubleshooting.
But yes, I would love to see the resolution to this problem. But I have my doubts, I've had many customers like this. They take the boat somewhere else, get it repaired and come back to tell me I was wrong. Trouble is the tech who fixed it had called me for advise.

 

[Captain of the Double G's]

Have you ever been part of a boat test for a magazine? I have, and I sure wouldn't use what they published as a substitute for actual testing.
The people who do these are trying to sell boat --- plain and simple. I've read the article (that's how I found out it takes 3-4 months from the test to published) about the test I was part of. They "bend" the numbers to make things look a "little" better.

I'll just be up front with you. I'm not here because I don't know how to fix this boat. I spent over 30 years as the guy people like you brought the boat to when they couldn't fix it themselves. You are here because you can't fix it yourself.

Your troubleshooting skills are weak.
Your reasoning seems flawed to me.
The testing you have done so far is incomplete.
The opinions you have are based some things you read on the internet --- but only when they agreed with your preconceived ideas.

"Does this drop affect issue with low vacuum which in your opinion doesn't exist - sorry but don't think so."
I don't care what you think, I don't care about a 555 table you found.
I work with facts not speculation.

Low vacuum is only a symptom, not a cause. And yes at this point I don't believe you have low vacuum.

I don't understand why you want to argue with the advise I'm trying to give you. If you want me to, I'll stop posting.

But, I will still try my best to help you.
Fix the voltage issue.
Fix the sea water pressure problem and while you're doing that, if you pull the drive -- count how many times the prop shaft spins when you turn the drive shaft 10 complete revolutions. Or if your just dropping the lower, buy a new o-ring for the top cap and count the teeth.
Try to get a good REC file.

I have been a repair tech for over 50 years and agree, thank YOU for posting all the crap I should have said.

 

[muc]

I have been a repair tech for over 50 years and agree, thank YOU for posting all the crap I should have said.

Yup, my claim to fame was two things.
I have made or seen just about every mistake ---- once.
I could handle the most "troublesome" customers with a smile.

But I will admit that I once told a V.P. of the largest boat builder in the USA that he couldn't use his boat 4th of July weekend because of a "safety issue". Because he been such a jerk to my favorite service manager. He sat in the marina all weekend with his friends and family.

 

[nola mike]

Once again, when you are done with your thesis, let us know. The rest of us would have replaced it all by now. Stop wasting our time.

Nah, most of us around here don't like to fire up the parts cannon if we can avoid it. Always free to move on rather than belittling people, since you've already made the same comment. As said before, this is a great thread for learning and problem solving.

 

[Captain of the Double G's]

Nah, most of us around here don't like to fire up the parts cannon if we can avoid it. Always free to move on rather than belittling people, since you've already made the same comment. As said before, this is a great thread for learning and problem solving.

YES , I wholeheartedly agree but there comes a time to start a new thread on the same subject to get new ideas ( IMHO ) My humble opinion is quite often incorrect but you mention problem solving. I never ever mean to BELITTLE anyone.

 

[Fun Times]

but there comes a time to start a new thread on the same subject to get new ideas ( IMHO )

With that, please bear in mind that It’s been a long running tradition to keep the same subject all on one thread and part of our guidelines here on this forum… had another one been created, one of the 10 forum moderators would have merged the threads together either when noticed or post reported by many other helpful, long term members that tend to feel the same way.