Mercruiser 6.2L 383 MAG Bravo II, Runs Rough, Guardian activated

[bupbup777]

Help Please,

I have a Mercruiser 6.2L 383 MAG Bravo II, Runs Rough, Guardian activated, Won't go above 3600RPM, The engine dies when throttle dropped to an idle after bringing up the RPM for a short period of time. I have it on a 29 foot commercial fishing boat. It ran fine last year, started acting up after 3 days this year. We were running on step, and the power dropped and brought us to a slow trot.

I had the 2 back to back Racor Filters with 2 micron filter changed, the Engine fuel filter changed. Checked fuel coming out of the fuel tank, Clear, clean. I also changed the High pressure Fuel pump. Replaced the High Pressure fuel pump regulator. It still is having the problem. Seems to shake a little. Changed the Distributor, After doing so it went to 3800RPM.

Unplugged the power to the low pressure fuel pump, felt the pump, then compared to when it was plugged in. It seems to be pumping. Also did this for the High pressure pump, seems to be pumping. Though multiple sources *Mechanics* say that we might have gotten a faulty new High pressure fuel pump. They recommend replacing it again.

We had a pressure gauge attached to see how much PSI the fuel was giving, was told it should hold steady at 38 to 40PSI. However, when we are running the motor at a idle it is bouncing anywhere from 25 to 35PSI. Sometimes it'll bounce to 40 PSI with RPM over a 1000.


We also bought a TechMate Pro Dyanostic tool for the Engine. Here are the results it remembered (Freeze Frame) when Guardian was activated.

Engine Speed 1320
Coolant Temp 125
Manifold Pres. 13.6
Barometric Pr. 14.5
Manifold Air Te. 116
Throttle Pct 30.0
Demand 30.0
Oil Level 0.0
Block Pressure 0.5
Battery Volts 14.1
Available Pow. 4
Engine Load 26.7
Engine Run Tim 265.1
fuel Per Cyl 0.0
Engine State RUN
Shift Position IN GEAR
Trim Position 0.0
Fuel Level 1 0.0
Port Tab Pos 0.0
Stbd Tab Pos 0.0
Lake/Sea Temp 0.0
Ray Boat Speed 0
Main Pwr RlyRe YES
Fault Freq Cou 2


Some of the Freeze Frame lists available other than Engine Guardian,

9 Engine Guardian
19 Maximum RPM Exceeded *Testing*
22 Warning Horn Out
75 Fuel Level 1 Ci....
94 Pilot Pressure



Any idea's where to check next?

 

[Fun Times]

Hi, welcome to iboats!

What year is the engine? Engine serial number would be much better to know too.

Coolant Temp 125...How long was the engine running when you recorded this info? Temp is to low if it's not reaching 163ish around 8 minutes of idle run time.
Manifold Pres. 13.6
Barometric Pr. 14.5
Manifold Air Te. 116...Hot Day that day if low run time?
Throttle Pct 30.0
Demand 30.0
Oil Level 0.0
Block Pressure 0.5.... Does this seem to fluctuate with RPM. While this seems low at 1300, are you seeing 8+psi in the mid 3000's RPM you are able to achieve?
Battery Volts 14.1 That's good.
Available Pow. 4.... When running normal, you'll see 100%
Engine Load 26.7
Engine Run Tim 265.1
fuel Per Cyl 0.0
Engine State RUN... That's good
Shift Position IN GEAR....That's good.
Trim Position 0.0
Fuel Level 1 0.0
Port Tab Pos 0.0
Stbd Tab Pos 0.0
Lake/Sea Temp 0.0
Ray Boat Speed 0
Main Pwr RlyRe YES... That's good.
Fault Freq Cou 2


9 Engine Guardian. you're seeing this cause you have an issue (fault) someplace...(The guardian is a result of other faults....Failed sensor).
19 Maximum RPM Exceeded *Testing*... Or possibly because you are trying to advance the throttle over the new preprogrammed RPM limit set within the ECM according to the available power %.
22 Warning Horn Out... Warning horn in boat not operating. No aubible alarm will be heard in the event of engine malfunction...Some issues could be, Horn failed or missing. Horn not connected. Horn circuit open.
75 Fuel Level 1 Ci....This is normal and ignored unless you have the fuel tank level sending unit connected to the smart craft system/gauge.
94 Pilot Pressure...... Same reason as fuel level.

You may want to pull some spark plugs and see what they look like. Especially if you believe you seen a gain after installing a new "Distributor assembly"? or did you mean new distributor cap and rotor?.
You may also want to perform an engine cylinder compression test to try and ensure nothing internal of the engine is affecting the fuel system such as this guy mentioned in the past....http://forums.iboats.com/forum/engin...ssure-bouncing

Just taking a guess of what fuel system you have without knowing the engine serial number, Was the little screen found under the fuel regulator clean or clogged with debris....Was it changed to a new one when you did the new regulator?..See item number 14, http://www.mercruiserparts.com/bam/s.../31954/7585/50

 

[bupbup777]

My S/N is 1G407210
Date 01/15/2015 *Installed* also punched on the engine plate

Does this seem to fluctuate with RPM. While this seems low at 1300, are you seeing 8+psi in the mid 3000's RPM you are able to achieve?
I'll look into this.

I installed a new new distributor cap and rotor. I also installed new Spark Plugs. NKG Iridium IX TR55IX (Stock Gap)


Regarding the regulator, Unsure my brother installed that. I'll have to ask.

 

[Fun Times]

My S/N is 1G407210
Date 01/15/2015 *Installed* also punched on the engine plate.

The following link is going to be your parts catalog for this REMAN engine model number 865108R80.. 383 MAG STROKER BRAVO-REMAN
http://www.iboats.com/383-MAG-STROKER-BRAVO-1G400000-UP/dm/view_id.1692522

Does the boat run in or sit in salt water? With the water pump psi possibly low, thinking just as a starting point you could have an issue such as this, http://www.amarket.com/BRAVOblock.htm

But there are many other reasons that it could be low too..Such as failing sea water pump impeller or impeller housing, water blockage somewhere, bad sensor, sensor clogged with debris or maybe just not enough RPM yet..

So for now, stay on repairing the engine temp if it's really that low....Start with a new thermostat and related parts.
Possibly water flow such as water inlet, impeller and sensor.
And definitely fuel pressure fluctuating.

 

[bupbup777]

In answer to some of your questions earlier,

Coolant Temp 125...How long was the engine running when you recorded this info? Temp is to low if it's not reaching 163ish around 8 minutes of idle run time.

Answer: New Thermostat, ran for about 15 to 20 minutes. We thought it might be a bad thermostat, so we had who we bought the engine from and they sent use a 165F thermostat to replace the one we had, the one we had was a 140F thermostat. Before replacing it the gadge showed 120F, after replacing it shows 160F.



Manifold Air Te. 116...Hot Day that day if low run time?

Answer: The Temp. that day was give or take 70F and it took about 2 hours to get to land when this first started acting up. It was hot that day as well.



Block Pressure 0.5.... Does this seem to fluctuate with RPM. While this seems low at 1300, are you seeing 8+psi in the mid 3000's RPM you are able to achieve?

Answer: Will check when I get back to the boat on the pressure at 1300 RMP's. I get it to 1300 RPMs and it seems to smooth out a little, run better, didn't shake as much.



Available Pow. 4.... When running normal, you'll see 100%

Answer: I will look at it next time I test the engine.



P.S.
We replaced the impeller, the old one looked new and no noticeable wear.

We have a Sanwan on the engine as well. We pulled the end caps off of it and used a airtank to blow out the cooling toobs. The cooling toobs blew out clean and clear. We also blew out the inlet, and all the water lines, they were clean and clear as well.

Regarding the Spark Plugs, they are brand new. I will see if I can find a compression tester to test the engine.



Any other idea's while I look into doing these suggested tests?

P.S. If I were looking into replacing this engine with a used and good Diesel engine. An engine that would mount up to the Brovo 2 bellhousing. Do you have any suggestions, or places I can look into it?

 

[bupbup777]

No Title

​I took some readings on the Engine today. Here are my results.


The Techmate Pro
Block Pressure
1.5 at 750 RPM
4.5 at 1400 RPM
5.0 at 1500 RPM
6.5 at 1800 RPM

Oil Pressure 56.6

Available Power
%100

Guardian State 1#

Fuel Pressure 2.1psi (Steady both at 671 RPM and 1280RPM)

High Pressure Gauge (Physical Device) 5-8 PSI at a 1000RPM (Steady both at 671 RPM and 1280RPM)



The engine is making a noice, it sounds like a rattle in front of the engine. Perhaps hydrolics or sump pump? *lubercated both while running, no change in sound*
Rattle like a self siphon hose makes at full flow. After a restart and warm up for about 15 min. it sounds like a ticking sound, the thermastat at the time was 132F and 1200RPM.


I also took photos of where I connected the High Pressure Gauge. I believe that is the right place to plug in, yes?
Also added photos of the Data the Diagnostic device displayed while the engine was running. See anything that might help?
I will check the Compression of the cylinders later, when I can get a hand.

 

[Fun Times]

P.S. If I were looking into replacing this engine with a used and good Diesel engine. An engine that would mount up to the Brovo 2 bellhousing. Do you have any suggestions, or places I can look into it?

Besides new from Mercruiser which will bolt up to a Bravo two drive but bear in mind that in some cases due to extra engine torque values, the upper unit housing components are considered to be better constructed to withstand the added torque of a diesel vs gas.... Also the gear ratio may have to be changed from what you currently have now as well. https://www.mercurymarine.com/en/us/engines/diesel/mercury-diesel/
https://www.mercurymarine.com/en/us...Overlay_IP=us&utm_campaign=Region+Redirection
http://sterndrives.com/414bravotwo.html

You may have to try doing a search online within your area for used mercruiser diesel engines including eBay. Or start calling some bigger marinas that tend to be working on bigger sized ocean designed boats possibly within your general area or outside of it too asking them if they have any good used diesels for sale.
http://boatswainslocker.com/content.aspx?file=customerpages/about.htm


For the other info, Yes that was the correct spot to connect a fuel pressure gauge to test the high pressure fuel pump system. Keep in mind that you seem to also have a lower pressure booster pump inline before the fuel filter according to the parts guide I posted above last night. The low pressure should be more in the 5 - 8 psi range while the high pressure pump should be no lower than 38 to as high as 43 psi. From the photo it seemed low and you mentioned 5 - 8 psi for the high side...If so that is way to low...Are you sure the pump is even turning on down there under the port side exhaust manifold behind the motor mount. If it's not that could be a reason why you don't have much fuel pressure should the low pressure pump be running the engine...Just guessing at this point. Here some fuel pump tips for you just in case, Electric Fuel Pump Troubleshooting - Marine Mechanic

The reason your scan tool Fuel Pressure reading of 2.1psi seems to be steady both at 671 RPM and 1280RPM would be due to your engine shouldn't have a fuel pressure sensor for the ECM to read so while it's misleading I know, you can't go off of that scan tool reading. It has to be the gauge you connected to the fuel rail as shown in your photo for accuracy.

Techmate Pro
Block Pressure
1.5 at 750 RPM
4.5 at 1400 RPM
5.0 at 1500 RPM
6.5 at 1800 RPM

Oil Pressure 56.6

Available Power %100

Those appear to be all good numbers and shows that the sea water pump impeller cooling system seems to be working okay at all those speeds. Hope they continue to go up as the RPM goes up to around 5000 RPM while staying with 100% power.

Was the boat in the water running/moving at the time of that reading..Just wondering as the scan tool says it's in forward? gear.

When it does (or did?) it's mishap, do you hear a warning horn going (beep) off?

All the readings on the scan tool seem to be okay at that time of reading. Do any of them seem to get worse at higher RPM's?

The new ticking noise would be concerning, are you able to determine the area it may be coming from.

 

[bupbup777]

Answers:

Was the boat in the water running/moving at the time of that reading..Just wondering as the scan tool says it's in forward? gear.
The boat was in the harbor/water. It was not moving. We discovered today that the shiftier was straight up, but it needs to be just slightly backward to have the engine be in full neutral. , not enough to get out of neutral but enough to make the scan tool think it was in gear.

When it does (or did?) it's mishap, do you hear a warning horn going (beep) off?
No alarm went off. When we did an alarm test with the scan tool, there was no sound. So either the alarm is not setup when the mechanic installed it or the alarm is faulty/dead.

All the readings on the scan tool seem to be okay at that time of reading. Do any of them seem to get worse at higher RPM's?
Not that I can recall, however I will look into it further tomorrow. We did discover that one of the spark plugs were misfiring. More on that in a bit.

The new ticking noise would be concerning, are you able to determine the area it may be coming from.
My brother discovered where it was coming from today. It was the belt, he noticed that the writing on it was going by in sequence with the noise.



Regarding the Misfiring. Looking at the engine, on the starboard side, second spark plug from the bow was not firing properly. It was a new Iridium spark plug.
We did a commpression test on all the cylinders. Here where the results.

---------------------Stern
190----------------------------------------------183
188----------------------------------------------183
140, 60, 50, 40, 20 (multi-testing)-------182
195----------------------------------------------194
----------------------Bow


We discovered that the Valve on that cylider with low pressure was not moving. Luckily we were able to see it from the Oil Cap being removed. When we turned over the engine a couple times to see if it was moving, it was not. My brother and father are thinking we have a sticky valve. We are going to look into it further tomorrow.
Suggestions? Likely cause of Guardian activating? We have an idea on how to loosen it up, we will try them tomorrow. Have any ideas?



My brother and I also did a TechMate Pro Induced Misfire Test. On the Port side, only number 1 fired consistently. The rest on that side did not fire during the test. One did once, weakly/small spark. However, when the engine is started normally, they all fire fine. Any idea why that might be?

P.S. we also changed the Fuel filter on the engine again. It seemed to help a little. That and putting the throttle back a hair to make the computer think it was in neutral.

 

[Jmunk]

Could also be a broken rocker arm or bent pushrod. Have to pull the valve cover and look. Shouldn't be hard to spot once the cover is off.

 

[alldodge]

This is probably right but I'm not seeing the location from this pic

It should be here and with both pumps barely pumping, I would start looking for a restriction in the tank pickup tube, collapsing fuel line or other restriction

Just for clarification the high pressure test should go here

 

[bupbup777]

We pulled off the valve cover. One of the valves adjustment nuts were snapped off. So the valve wasn't moving. We are ordering parts to replace it in the morning.

Keep you posted.