Mercruiser 5.0l MPI running data. Check mine and check yours!

[matthewmiller01]

I ran the boat for the longest sustained period as I ever have this weekend. We cruised up to downtown Knoxville for an overnight trip for Boomsday. Anyway, it was a good run on plane and I spent almost an hour at near constant speed. I did the best I could to gather engine data so that I would have some baseline information for future troubleshooting. Here it is, in case anyone wants to bounce their data off mine to see if either one of us may have something going bad.

The engines are 5.0l MPIs in my 2008 290DA.

RPM:
Port - 3450 rpm
Stbd - 3440 rpm

Fuel Burn:
Port - 11.4 gph
Stbd - 11.0 gph

Oil Pressure:
Port - 61.4 psi
Stbd - 61.5 psi

Water Pressure:
Port - 7.7 psi
Stbd - 7.4 psi

Engine Temperatures:
Port - 156F
Stbd - 158F

Speed: 27.5 mph

Trim Tabs: Fully Up

Drive Positions: Fully Down (0)

Generator Status: Running (although I don't think any of these numbers would change if it were not running)

All of this data was gathered off of my Smartcraft gauges at the helm.

If anyone has anything different on their engines or sees a problem with any of my data, please let me know and I hope this helps out others.

One question... does Smartcraft actually use some measured fuel flow or does it just calculate fuel flows based on injector pulse rates (assuming factory installed injectors)?

 

[Cincy Aquaholic]

That's great. I will be doing an hour cruise when I hit lake Cumberland and will see if I can document mine.

I do believe my oil pressures run a tick lower at cruising speed but that's based on the analog gauges. And mine typically runs 158 and 163 degrees.

Your fuel burn will be a little bit affected by genny running. Maybe 1 gallon for that hour?

Any reason not to trim up a little? I notice a pretty decent difference in speed and mpg when I trim up a couple ticks.

 

[ardeprint]

...Any reason not to trim up a little? I notice a pretty decent difference in speed and mpg when I trim up a couple ticks.

I agree... Was the water rough?

 

[matthewmiller01]

That's great. I will be doing an hour cruise when I hit lake Cumberland and will see if I can document mine.

I do believe my oil pressures run a tick lower at cruising speed but that's based on the analog gauges. And mine typically runs 158 and 163 degrees.

Your fuel burn will be a little bit affected by genny running. Maybe 1 gallon for that hour?

Any reason not to trim up a little? I notice a pretty decent difference in speed and mpg when I trim up a couple ticks.

Great! Please do. I am curious to see any difference. (I am also going to post these numbers in the 290 thread.)

As for the genny... I am not sure, but I don't think that it would affect the engine fuel burn calculation for either engine, right? I do know that, fully loaded (I am not sure we could ever fully load a 5kw genny - I know I didn't have it fully loaded), the genny will burn just under 1 gph. So you're estimate was correct. Back to my question, does anybody know how fuel burn is calculated by Smartcraft? Is it actually measuring flow to each engine or is it calculating fuel usage based on engine speed and, therefore, injector pulses and the designed injector fuel flows per pulse?

As far as trimming up (the drives, I assume)... I have played around with them and have found absolutely zero increase in speed and no change in the rushing water sound off the hull (two things I used explicitly on my 210SEL to ensure the best economy). Once I get to about 4 on the trim indications, the speed starts to drop off. I don't know that this is right or wrong (you two now lead me to believe that it may be something wrong). I THINK it would be more the tabs positioning vice the drives, no? :huh: But if I use more tab, I will plow more and put more hull in the water, and lose speed, right? I will have to do some more investigating and playing around with both the trim tab and the drive positions.

I agree... Was the water rough?

Nope, other than the wake from the occasional larger boat headed downriver. The water had a little bit of debris (sticks and wood from dock consruction) from the recent winds and rain, but not a lot. It wasn't glass-like, by any stretch of the imagination, but it was calm. There was only a slight wind.

 

[skolbe]

Your water pressure seems low compared to 350 mags on my boat. Mine are usually around 12 psi.

 

[Cincy Aquaholic]

Hmm interesting that you don't note any improvement with trimming the drives up. Yes I was referring to the drives. I rarely use trim tabs unless I need to offset a big weight imbalance.

But I always trim my drives up on a smooth lake at cruise speed. I go by feel and not the gauge number but I would say around 4 or so I will pick up a couple mph and the motors will rev more freely. I think I've seen about .1 to .2 increase on the mpg. I trim up to below the level of it porpoising. Heck I can even tell where the water planning of the hull goes back further.

Using tabs will push the bow down so if they are all the way up then your drives should bring the bow up when trimmed right.

 

[matthewmiller01]

Your water pressure seems low compared to 350 mags on my boat. Mine are usually around 12 psi.

Interesting. Could this be engine dependant (where 12 psi is normal for the 350MAGs and 7.5 psi is normal for 5.0l MPIs? Can anyone validate this?

Hmm interesting that you don't note any improvement with trimming the drives up. Yes I was referring to the drives. I rarely use trim tabs unless I need to offset a big weight imbalance.

But I always trim my drives up on a smooth lake at cruise speed. I go by feel and not the gauge number but I would say around 4 or so I will pick up a couple mph and the motors will rev more freely. I think I've seen about .1 to .2 increase on the mpg. I trim up to below the level of it porpoising. Heck I can even tell where the water planning of the hull goes back further.

Using tabs will push the bow down so if they are all the way up then your drives should bring the bow up when trimmed right.

Yes, I have tried to adjust the drives and the trim tabs, but have not noticed any improvement. As I said, I will keep trying. Based on having a bowrider prior to this (where I always trimmed to the best feel), I do try to "feel" the best ride for the boat.

So, by you seeing the fuel economy change when you adjust the trim, that does seem to verify that there is some type of actual fuel flow measurment going on vice a calculation of fuel flow.

When you are running "right", about where is the water planing off the boat? On this trip, the water was just about right under the helm (dash itself, not me or the helm seat).

Also, I thought I remembered reading somewhere on here about changing the drive actuator "Sleeve" things to allow for more (or better) drive adjustment. Am I remembering this correctly or was that specific to my 210SEL?

 

[matthewmiller01]

OK, everyone. Here is another data run. Conditions were fairly calm. This was about 45 minutes into an ~hour and a half run.

The engines are 5.0l MPIs in my 2008 290DA.

RPM:
Port - 3440 rpm
Stbd - 3450 rpm

Fuel Burn:
Total - 22.61 gph
Port - 11.0 gph
Stbd - 11.2 gph

Oil Pressure:
Port - 59.6 psi
Stbd - 56.5 psi

Water Pressure:
(New impellers one month and ~5 engine hours ago.)
Port - 15.8 psi
Stbd - 7.1 psi (I believe I have a bad pressure transducer, but haven't troubleshot it yet to be sure.)

Engine Temperatures:
Port - 156F
Stbd - 156F

Speed: 24.8 mph (GPS)

Trim Tabs:
Full Up

Drive Positions:
Port - 2
Stbd - 2

Seawater Temp:
80F

Air Temp:
78F

Loadout:
~105 gallons of gas at the time of data taking
28 gallons of water (full)
0 gallons of waste (empty)
4 adults and 4 children on board
Heavy loadout (IMO) due to plans on overnighting

Generator Status: Running (although I don't think any of these numbers would change if it were not running)

All of this data was gathered off of my Smartcraft gauges and System View at the helm.

Comments?

 

[julians]

To throw a bit more data into the mix, this was taken from my 2006 5.0mpi.


oil pressure@3000rpm= 60psi
oil pressure@750rpm=45psi
coolant temp@3000rpm = 160f

 

[firecadet613]

Interesting how your water PSI is so high on that engine. I've got one at 7PSI and one at 2PSI, swapping out the pressure senders did nothing. May be replacing an impeller.

 

[KP49]

Interesting how your water PSI is so high on that engine. I've got one at 7PSI and one at 2PSI, swapping out the pressure senders did nothing. May be replacing an impeller.

At 3700 rpm I see 3.5psi with a single 350mag/b3 with a new impeller, old impeller was 2.5psi at the same rpm. Off plane it will go to 7-10psi until it gets on plane then it drops off. I took the sender out the other day and tried to clean out the tiny hole and now I see 5psi @3700. I havent seen any official numbers what the water pressure should be, but if nothing is running hot after an hour at 3700rpm in 82 degree water it must be moving enough water so I'm not going to worry about it.

The impeller housing was in good shape, old impeller looked fine, backflushed the inlet hose on the lift and it flowed plenty of water.

As far as other numbers for a one hour cruise:

3700rpm
24-25mph GPS
11.6GPH according to the Smartcraft gauge.
158 degrees water
57psi oil pressure (25w40)

 

[firecadet613]

Thanks. I get no alarm and temp is 158 Port and 159 Starboard.

 

[KP49]

Thanks. I get no alarm and temp is 158 Port and 159 Starboard.

I wouldnt worry too much about it then, I have had Volvos for years and they never had a pressure monitor so I never sweat the water pressure readings. From what I understand they use a 0-50psi sender so most likely on the bottom end of the range it isnt that accurate. Not to mention too much pressure could indicate a blockage somewhere and not necessarily be a good thing. Hard to tell since the service manual really doesnt have a min/max spec that I could find anyhow.

After the boat drains out on the lift it takes a few seconds for pressure to build up and it sits .2psi for a bit and that doesnt set the alarm off so I guess anything over zero is good for merc lol.

 

[firecadet613]

Thanks. My last two boats were VP, and up until I installed the SmartTachs a few days ago I didn't even have this info. Temp is all you need after all!

 

[Fun Times]

Hard to tell since the service manual really doesnt have a min/max spec that I could find anyhow.

Specifications from a diagnostic service manual.:thumbsup:

The seapump sensor measures water inlet pressure or water block pressure. Normal diagnostic tool ranges are 1-5 psi (7-34 kPa) at idle and 7-17 psi (48-117 kPa) at WOT. To check if sensor is within range, the diagnostic tool reading with key ON should be approximately zero. The normal resistance value for the Sea Pump, Oil, Pitot Pressure are,
A to B 31.5 kohms and A to C 42.9 kohms.
A malfunction of the sea pump sensor will set the fault of Seapump CKT Hi, Seapump CKT Lo or Seapump PSI Lo.
​

 

[KP49]

Specifications from a diagnostic service manual.:thumbsup:

The seapump sensor measures water inlet pressure or water block pressure. Normal diagnostic tool ranges are 1-5 psi (7-34 kPa) at idle and 7-17 psi (48-117 kPa) at WOT. To check if sensor is within range, the diagnostic tool reading with key ON should be approximately zero. The normal resistance value for the Sea Pump, Oil, Pitot Pressure are,
A to B 31.5 kohms and A to C 42.9 kohms.
A malfunction of the sea pump sensor will set the fault of Seapump CKT Hi, Seapump CKT Lo or Seapump PSI Lo.
​

Didnt look in the diagnostic manual for that, you would think it would be mentioned somewhere in the engine manuals what is acceptable. Thats a pretty wide range, good to know though.