Just got my injectors back from service and they have the following numbers (cc):

Static
1: 390
2: 389
3: 393
4: 394
5: 391
6: 375
7: 389
8: 390

Dynamic
1: 341
2: 340
3: 343
4: 344
5: 343
6: 329
7: 340
8: 340

Should I be concerned about number 6? The engine is in a 30ft cruiser that won't do much (or any) WOT. It'll probably live its life around 2000-3800 rpm. Yeah model 2003, 300 hrs.

I've read that the fueldelivery is critical on these engines due to a kind of weak spot on the pistons, hence why I sent them for a check and service. I don't want it to blow up...

I wouldn't be worried. It appears to be the same percentage difference before cleaned and after cleaned. Looks like you sent in some good injectors to be cleaned and they came back a little cleaner.

It's really a question of what's the lowest limit of flow rate can be before there's a reason for concern.

Imo static flow doesn't mean anything. Did they test them at different pw?

I bought a injector flow machine a few weeks ago. Was always wondering what the injectors were doing. The lower pw is where you see a bigger discrepancy from what i have seen. When i flow them at lower pw, there can be a bigger difference.

Your lowest injector is flowing about 4% lower than your highest. Which one is closer to spec? A 4% spread isn't bad. Merc runs a safe tune.

Also each cylinder will have a different fuel requirement because the air flow isn't the same across all the cylinders. If you can, put that injector in the cylinder that the plug reads the richest/ coolest.

Most average older style injectors new were +/- 3-4% of mean average out of box. When I have tested new oem 496 injectors they were within +/-2% of the average. It looks like your mean average of flow on that dynamic test is about 340 so # 6 at 328 is about 4% low. If I was doing them and had a new identical injector available, Id say its a option to replace the low one but its not as dramatic as the graph makes it appear. As mentioned, their test doesnt appear to be that "through", when I do them, I run them thru 8 different test after running them for 20 minutes to fully warm them up to make sure they dont decay hot. Also as mentioned, they tend to flow further apart at lower rpms/on/off time BUT its also not as critical because no one going to melt a piston at 1000 or 2500 rpms at 10 or 15% throttle.