Jumping tach on Vessel View 7 - 6.2L Mercruiser (2004)

[Zixxer]

Hi, I've read through endless postings and most of the data is related to analog gauges, but I understand the underlying troubleshooting may be the same.

Situation:
Just replaced a 6.2L MerCruiser on my 2007 Sea Ray 310 - only 130 hours on both motors, but the port engine scorched a piston after overheating when we sucked up something on the Potomac River. It was very sudden and the guardian system kicked in, but not quick enough to avoid the temps that basically seized a wrist pin. The engine ran, but had piston slap. Sorry, not really the issue, just explaining how we got here.

So, replaced the setup with a MerCruiser factory long block. Did some preventive maintenance and replaced the transom water pickup tube assembly with the new version, replaced the cool fuel 3 module and injectors (found paint in the module and MerCruiser replaced it under a customer care program), new plugs, new wires, new cap, new rotor, oil, etc. Initially I didn't pickup on it as I keep the motor at 3,000 RPMs and below for the first five to ten hours, but the tach would jump a bit on the port (nothing on the starboard) and I would feel a slight miss as we went higher in the RPM range. That prompted the fuel module and injector change, the mechanic suspected the injectors were bad and attempts to clean them ended up with just replacing them. Thought for sure that would address the issue but it hasn't. Mechanic says he swapped the ignition coil from the other motor and no change.

So I've personally checked every plug wire to ensure they are installed correctly and not just resting across other wires. Unplugged and rechecked every connection on the engine harness, honestly they all look pristine. The mechanic says his diagnostics show the engine is running fine and no codes are throwing.

I call to MerCruiser yields something about a "filter" in the vessel view setup that either accounts for or creates this variation. I don't buy it, and it wasn't an issue before. I think if anything the Vessel View is more sensitive to showing issues and there's something amiss (no pun intended).

So I intend to check the following after reading for weeks online:

1. Grounds to the block. Since this can easily get sloppy by moving parts over, perhaps it's that simple and some greasy hands or poor surface prep is in play.

2. Swap the ignition coil myself, I'm not sure that was really done as I believe the mechanic was betting solely on the fuel injectors as being the issue. He's a super great guy, but so busy that I think these issues can just overwhelm the business.

3. I cannot confirm if I have a hall effects sensor - parts catalog says it's not sold separately. If one is present, I will either test it or swap from the good engine.

4. Cam sensor - long shot, but perhaps it's dirty, either the connection or the sensor face.

5. Swap the vessel view plugs at the helm to display on the opposite side just to eliminate the wiring harness. I think this is long shot as well given it was working perfectly before.

I'm convinced it's something simple and related to the motor installation.

I welcome any advice in this troubleshooting process.

Video link to what it looks like:

https://1drv.ms/f/s!Apeu2tS2JTo2hup01kXpsyzcbKDX_g

 

[alldodge]

Howdy and sorry for not responding sooner.

port engine scorched a piston after overheating when we sucked up something on the Potomac River. It was very sudden and the guardian system kicked in, but not quick enough to avoid the temps that basically seized a wrist pin

First engine scorched a piston do to overheat. but its the sized a wrist pin is not found in an overheat issue. The overheat does burn a piston, gall rings and others, but the wrist pin is my puzzler. In many cases the mechanic states all kinds of first impressions and some are right but I find in most cases there not. Not saying their lying, just not enough info to make an evaluation, just enough to get Merc or someone else to say OK.

Sense this goes on at 3K and above rpm, I would lean more to fuel pressure related. I would be interested in seeing what the fuel pressure is throughout the rpm range

 

[Zixxer]

I have the scorched piston on my desk at work, just know that's the item that failed or took the toll on the engine when it over heated. It's really not the issue at hand.

Fuel pressure on the VV7 display is 46.2 (going off memory, but that sticks in my mind) and it's steady.

This weekend I checked all of the harness connectors, removed some of the dielectric grease that I know was coil wire leads (v. boots) and no change. The wires and connectors are spotless and I applied dielectric grease to the coil post (outside) as indicated in the manual.

I do note the orientation of the distributors are about 10 degrees different from engine to engine?

Had a short weekend but will put the Diacom software on it next weekend to get a tach reading to see if I'm hearing a miss or just imaging it.

 

[Zixxer]

Checked my videos last night and fuel pressure is 42.9 on each side and steady. Those readings are consistent from last year as well.

 

[alldodge]

Checked my videos last night and fuel pressure is 42.9 on each side and steady. Those readings are consistent from last year as well.

Recon I can forget fuel pressure. Next thing I would look at would be the cam and crank sensors.