Brand New Mercury Reman 300XS (just out of break-in) Surging/Skipping on the Top End

[Savage]

The later air compressors are not quite as tight as the earlier versions- most will make it to approximately 110 psi (seldom will one achieve above that). Don't fail one strictly on that unless it is EXTREMELY lazy getting there.

If swapping gauges provides similar results, I would recheck the pressures at 1000-1100 RPM's and make sure the differential (delta) is within spec.

Otherwise not anything I'm concerned with from those numbers....

I rechecked the pressures at 1000-1100 RPM's and had 90 PSI Air and 104 PSI Fuel.

Checked the Air and Fuel pressures at the river at ALL RPM's and I don't see any pressures dropping out, or fluctuating, yet the problem is still there. The motor wont pull more than 5600 RPM.
I tried to make data recordings with the Rinda software, but apparently when I closed the lid on my laptop the recordings stopped.........dammit!

Came back home and installed all new spark plugs.
Also inspected all the grounds on the coil plate and coil plate to motor mounting surfaces.

[JOE54]

does it still feel like its surging /skipping ,does RONDA have a cyl drop test to isolate problem cyl

[Savage]

does it still feel like its surging /skipping ,does RONDA have a cyl drop test to isolate problem cyl

Yep does the same skip. I get the bow flying high, then it skips and drops, then comes back up, skips and drops. Other motors ran at +6000 RPM, this one tops out at 5600. Thing runs like a 250 HP.


I'll have to check to verify, but I think Rinda does have a drop test.

[JOE54]

would be nice to isolate which cyl is causing problem

[EuropeanAM]

If you can get someone to ride with you and work the Cylinder Misfire tests- that would help greatly. Try to do it as close to WOT as possible, record the RPM drop for each cylinder. At least this way we can focus on the air/spark/fuel related to that specific cylinder.

[Savage]

WOT in my boat is shall we say "on the edge". I'm going to have to figure out how to safely do that, with my Son.

My list is down to:
Coil/harness interrmitant operation.
Map
TPS
Turned sleeve
Injector

I wish the dam thing would throw a code at me !

[EuropeanAM]

Been there, done that. What I've done several times is to back the trim down/lower (dropping the RPM's a couple hundred but also keeping a little better "bite" on the controls).

Usually I'm still able to ascertain a difference if it's on WOT.

[Savage]

New spark plugs and coil plate grounds made NO change. I ran it tonight on the river, but without the computer. Still could only muster 5600 RPM.

[JOE54]

you got bore scope to look at ports in cyls not seen an opti with sleeve turned that had skip/surge

[EuropeanAM]

Seen a few turned, but like Joe said, no "surge or skip" (just down on power).

[Savage]

Last night it topped out at 5600 RPM then fell to 5400 RPM, and just keeps repeating, so that's why I'm calling it a surge. So its hitting a wall, then falls back and starts to climb again. Like a miss but delayed, not rapid fire.

Feels Dam close to how a rev limiter feels, but a lot softer. Does Mercury cut out fuel injectors, with spark, in the rev limiter program?

[lpugh]

I am curios Savage when you checked pressures on the water did you also check the low pressure as well. This is only theory but I have seen cases in the old days of carburetors and vapor locking issues where fuel would become aeriated (foamy) and pressures would still be ok, but because of the foamed fuel it would be very lean. My thinking being that low pressure could be a little low but the high would still be good. Anything to foam the fuel could cause this
Sure sounds like a fuel starvation symptom

[Savage]

Diacom has an "Induced Misfire Test" which disables the fuel injectors for each of the 6 cylinders, at a varying percentage, which last about 15 seconds per cylinder. It should be identical to a Mercury CDS drop test. According to Rinda all the tests that a Mercury CDS can perform are in the PCM and Rinda's testing just activates those tests that have been established by Mercury.

Leon I did check the low pressure on the water @ WOT and the pressure was 20 PSI.

Tomorrows plans are:
Run the boat @ WOT with a 6 gal remote fuel cell.
Perform Induced Misfire Test @ WOT for each cylinder. Induced Misfire Tests can not be recorded, so I have to rely on the tach, GPS, and seat of the pants feel.
Make several recordings @ WOT to review the running parameters in action.

I have a new coil and MAP sensor that I can try depending on the data.

[lpugh]

Look at the bright side of how much we will all learn from your misfortune

[Savage]

Look at the bright side of how much we will all learn from your misfortune

I just a had a feeling from the beginning that this one wasn't going to be easy to find.......kinda why I'm documenting it.......Enjoy

[JOE54]

MAP first please

[lpugh]

Will the Diacom let you monitor a single PID (sensor) in a graph view, I do this with automotive scanners, when viewing only one pid (sensor)the data is almost like using a scope (faster updates), If so this would allow you to see exactly what the map signal is doing. As you know I am an automotive guy so no experience at all with outboard scanners. But at WOT the map should match very closely to the voltage at key on engine off, suspect 4.5 to 4.9 volts since it think it is a GM Delphi sensor, Graphing mode give a really good visual of what's going on without having to read the numbers.

[Savage]

MAP first please

Yes Sir!

Leon it is a GM map sensor and the readout is in PSI. I can also graph it. Currently it reads about 13.66 PSI at idle, and around 14.0 PSI, with just the key on.

[Savage]

Ran a lot of tests today @WOT, with my Son running the lap top, and saving and addressing files.

The Map sensor made no difference. The only sensor I could find locally to test was GM #12614970. I'm hoping it was compatible.
Ran the boat on a 6 gallon fuel tank, made no difference.
Did a coil swap dance. Put a brand new coil on cylinder #1, then put coil #1 on cylinder #2, then put coil #2 on cylinder #3, then put coil #3 on cylinder #4, then put coil #4 on cylinder #5, then put coil #5 on cylinder #6........No change.
Had my Son pumping the primer bulb @ WOT in case the pulse pump was weak.....No change.

Did a cylinder drop test beginning @ WOT (5600 RPM) and ending @ WOT. Results are below.
Cylinder #1 RPM dropped to 5100 and came back up to 5600
Cylinder #2 RPM dropped to 5090 and came back up to 5600
Cylinder #3 RPM dropped to 4800 and came back up to 5600

The above tests were on the small 6 gallon tank. The below tests are on the boat tank because we ran out of fuel in the 6 gallon tank.

Cylinder #4 RPM dropped to 5090 and came back up to 5600
Cylinder #5 RPM dropped to 5060 and came back up to 5600
Cylinder #6 RPM dropped to 5010 and came back up to 5600

I have 13 Rinda Diacom files, with the problem occurring on EVERY file.

Don and Joe can you guys review some of the files for me? If so PM me the email address that you would like the files sent to. Hopefully you can view the data, without having the Diacom software.

I reviewed 385 packets of data at a play speed of 1000 MS, while the motor was at 5400- 5600 RPM, and the problem was active.
The TPS stayed at 4.48-4.53 the entire time that the motor was at WOT.
The MAP stayed at 13.99-14.25 the entire time that the motor was at WOT.
The battery voltage stayed at 13.79-14.16 volts the entire time the motor was @ WOT.
The block pressure stayed at 25.26-26.44 PSI the entire time the motor was @WOT.
The RPM's fluctuated between 5657-5327 the entire time the motor was @WOT
The engine load percentage fluctuated between 81.55-86.58.
The charge Temperature, which I believe is the MAT fluctuated between 86.00-93.20 *F.
Both the starboard and port cylinder temps stayed between 118.40-120.20 *F.
Motor stayed IN Gear.
Demand 100%
Available Power 100%
Throttle Percent 100
Power limit Set Point 100%
Sensor Power 5.02-5.03 VDC
Sensor Power Two 4.97-4.98 VDC
Fuel Flow Rate fluctuated between 24.85-26.30 GPH
Air compressor temp 104-107.60 *F


I borrowed a bore scope from work, but I'm saving that test as a last resort. I'm really not sure if its even possible to get a good look at the ports any way.

Running out of Ideas though!

[EuropeanAM]

I don't see anything in the Cylinder Misfire Test *** that screams "rotated sleeve". Most commonly we see 400-500 RPM drop on a misfire test (you do have several REALLY strong cylinders if those numbers are repeatable).

I do not think that I'm able to play-back the Diacom files without the software.

Try the Auto Self Test (Plugs OUT of Cylinder Head) and listen carefully to the DI's as they function. You should here a "circular" (cyclic) pattern as they are running- if you hear anything that sounds like stuttering or non-cyclic, you probably have a DI or two that are not functioning properly. Yes... I know they're new (but that doesn't mean they're good).

*** Misfire test strategy (it's a PCM feature) is to never run the engine lean. At idle, it ADDS FUEL. At WOT, it SUBTRACTS SPARK.