Engine Overspeed?

[JCJC]

I had the data dumped from the ECM on my new to me 2007 Chaparral 204 SSi with a 5.0L MPI engine. The data confirms what I saw on the analog tach; I ran the engine at 5400 rpm for a few minutes. Since then, I discovered that the engine spec is 4600 to 5000 rpm WOT. Shouldn't the rev limiter have kicked in? Is there a part that I can replace to make sure the rev limiter works next time? Below is a portion of the ECM data.

DIACOM MARINE SERVICE REPORT ​

12/07/2023 08:57:28

1. VEHICLE CONFIGURATION
Cust. Name:
Engine Make: MerCruiser 5.0 mpi
Engine Serial No:
Model Year: 2006
System Type: MerCruiser PCM555

3. TROUBLE CODE STATUS
Current ECM Codes
Sensor Fault, click Read Fault button for details

Freeze Frame Data:
8 OVERSPEED
--------------------------------------------------------------------
FF Baro Pressure 14.41 PSI
FF Battery Volts 14.08 VDC
FF Sea Pump Pressure 14.92 PSI
FF Boat Speed 10.00 #
FF Manifold Air Temp 78.80 °F
FF Coolant Temp 154.40 °F
FF Demand 96.07 %
FF Engine Speed 5149 RPM
FF Engine State Running
FF FPC Total 0.0 Counts
FF Frequency Count 149
FF Fuel Level 0.00 %
FF Gear Position In Gear
FF Lake Temp 32.00 °F
FF Engine Load 34.78 %
FF Main Pwr Relay Requests YES
FF Manifold Air Pressure 14.00 PSI
FF Oil Level 0.00 %
FF Port Tab Pos 0.00 %
FF Available Power 100 %
FF Run Time 326.45 hrs
FF Starboard Tab Pos 0.00 %
FF TPS Percent 96.07 %
FF Trim Position 0.00 %

Fault Log Data
Fault Descriptions Seconds
Battery Range High: 0
Battery Range Low: 0
Block Pressure is Low: 0
Compressor Temp Overheat: 0
ETC Motor Open: 0
ETC Motor Short: 0
Fuel Pressure Sensor Input High: 0
Fuel Pressure Sensor Input Low: 0
Guardian Strategy: 0
Knock Sensor 1: 0
Knock Sensor 2: 0
Low Oil Pressure Strategy: 0
Low Oil Remote Strategy: 0
Low Oil Reserve Strategy: 0
MAP Sensor 1 Input High: 0
MAP Sensor 1 Input Low: 0
MAP Sensor 1 Idle Rational: 0
Oil Pump Output: 0
Overspeed: 14
Port Clnt Overheat: 0
Starboard Clnt Overheat: 7
Warning Horn Output: 270
Water In Fuel: 0
Engine Run Time History:
Total engine run time: 326.63 Hours

0 - 749 RPM: 147.70 Hours
750 - 1499 RPM: 87.93 Hours
1500 - 2999 RPM: 53.80 Hours
3000 - 3499 RPM: 26.92 Hours
3500 - 3999 RPM: 7.78 Hours
4000 - 4499 RPM: 1.73 Hours
4500 - 4999 RPM: 0.70 Hours
5000 - 5499 RPM: 0.07 Hours
Over 5499 RPM: 0.00 Hours

​

 

[alldodge]

Your motor is working as it should.

Motor hit something between 5000 and 5499, so meaning 5000 exactly or anything above it like 5001 or above. This was also just .07 tenths of 1 second

Over Rev can happen when the motor is trimmed up to much. IMO don't worry about it unless it keeps happening.

 

[JCJC]

Your motor is working as it should.

Motor hit something between 5000 and 5499, so meaning 5000 exactly or anything above it like 5001 or above. This was also just .07 tenths of 1 second

Over Rev can happen when the motor is trimmed up to much. IMO don't worry about it unless it keeps happening.

Isn't it .07 of an hour, or 4.2 minutes? But I agree that it might have been just 5000 rpm. At what rpm does the rev limiter and/or an alarm kick in? When I pushed it to full throttle, I didn't feel any deceleration, didn't hear an alarm. I would have thought that I would feel the rev limiter working. Since then, I installed VesselView but the boat is stored for the winter so all I have to go on is what I saw on the analog tach.

 

[alldodge]

Your motor is being protected
If you want the RPM lowered so this will not happen \, increase prop pitch or increase prop cup

 

[Scott Danforth]

You don't have unlimited fuel mapping to allow the motor to damage itself.

 

[JCJC]

You don't have unlimited fuel mapping to allow the motor to damage itself.

Scott. Can you explain that in a little more detail? Thanks.

 

[Scott Danforth]

Scott. Can you explain that in a little more detail? Thanks.

Your MPI engine is run by the ECU. The ECU has fuel mapping that stops at about 5400 RPM. The spark mapping stops there as well. So the motor will never be able to reach a higher RPM on its own as it stops fueling and spark.

 

[JCJC]

Your MPI engine is run by the ECU. The ECU has fuel mapping that stops at about 5400 RPM. The spark mapping stops there as well. So the motor will never be able to reach a higher RPM on its own as it stops fueling and spark.

OK. Fuel flow doesn't increase after 5400 rpm so the engine won't spin any faster than that, but is it OK to run it at that rpm for any length of time when the WOT spec is 4600 to 5000 rpm?

 

[dingbat]

O but is it OK to run it at that rpm for any length of time when the WOT spec is 4600 to 5000 rpm?

No, it’s not ok for any length of time.

Limiting top end rpm to within rated rpm range is done by prop selection.

You need to learn not to push the throttle to hard or increase the pitch of your prop

 

[JCJC]

No, it’s not ok for any length of time.

Limiting top end rpm to within rated rpm range is done by prop selection.

You need to learn not to push the throttle to hard or increase the pitch of your prop

OK. Thanks. I only had the boat out twice last season and only one time when when Lake Michigan was flat enough to go full throttle. I'll get the hang of it next year. If I post the full ECM dump, can you tell me if there are any other faults that I should look into over the winter?

 

[Fun Times]

Where it says “Engine Speed 5149 RPM” suggests you went that RPM at some point or another which is over your specifications but just shy of turning on the rev limiter by I relatively believe .1 RPM as the limit should be set to go off at 5150 which is usually written in the books at 150 over top end specifications.

What was the boat load weight wise when you went at RPM? Was it s light load?

 

[JCJC]

Where it says “Engine Speed 5149 RPM” suggests you went that RPM at some point or another which is over your specifications but just shy of turning on the rev limiter by I relatively believe .1 RPM as the limit should be set to go off at 5150 which is usually written in the books at 150 over top end specifications.

What was the boat load weight wise when you went at RPM? Was it s light load?

Just me and 1 passenger.

 

[Fun Times]

Just me and 1 passenger.

Welcome to your wide, open throttle speed run of the day.

 

[Leardriver]

What would it cost to buy a scanner that would provide that sort of data?

 

[Stinnett21]

I rarely run WOT but I have heard my 5.0 MPI reach the limiter twice in the 19 years I've owned it. As Fun Times said right around 5150 I heard a somewhat faint beeping. That was all she had and conditions had to be perfect to reach the limit. Quickly backed it off.

 

[Fun Times]

What would it cost to buy a scanner that would provide that sort of data?

Look up Rinda technologies handheld or diacom scanners...They tend to start right around $500.00...You can but direct.

Rinda Technologies Inc. Marine and Industrial Engine Diagnostic Tools

And/or, someone on ebay offers a rental program at times.

Rinda Tech for sale | eBay

Get the best deals for Rinda Tech at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

 

[JCJC]

What would it cost to buy a scanner that would provide that sort of data?

The marina charged me $135 to download the data and email it to me. There is a lot more than the bit that I posted. The scanners I've seen cost about $600. For the very few times I'd use one, it's more cost effective to let them do it.

 

[alldodge]

It took them probably 10 minutes total. A scanner is a must have for the new motors

 

[Leardriver]

I am of the belief that you can't own a modern car without a specific scanner. I have 6 different brands now.

 

[JCJC]

I am of the belief that you can't own a modern car without a specific scanner. I have 6 different brands now.

You can if you pay a qualified mechanic to work on it.