Mariner 60 EFI 2003 - Not reaching max rpm

Hi everyone

Earlier this year i bought a used boat with this engine.
I have some experience with boats, but not outboards.
I kinda feel like it's not running at it should.

I mounted Bluetooth smartcraft to get more than rpm tach info.
Running a little rough on idle between 800-900rpm cold and warm, sometimes 1000.
iac valve is changed.
Max 5000 rpm WOT, last owner meant he got more. I have a 10 1/18 x 15 prop. The boat is around 600-650kg with engine, 17 feet.
Oil pressure on smartcraft is around 396 kPa, which sound high for me?

The engine had service with dealer end of last season, but i changed sparks, fuel filter and hoses, iac valve, gear oil and water pump this summer too. Sparks was a little wet, i think i have some photos. There is spark on all.
Also some transparent exhaust smoke, mostly in idle.

What do you guys think?
Thanks!

Video idle https://m.youtube.com/watch?v=Umco-xOT3Zw

Next step would be a compression test both cold and hot would be good, making sure throttle wide open. Which reminds me, its time for me to get a new gauge.

timguy said:

Next step would be a compression test both cold and hot would be good, making sure throttle wide open. Which reminds me, its time for me to get a new gauge.

Click to expand...

Thanks for the tip, i will buy a compression tester. But do i test while trottle wide open?

Do you agree that it's running a little rough on idle? I think the manual says 725 +/- 25 rpm

Not bad idle. WOT for test especially important on 4 strokes.....in your case it will support slightly higher numbers. Think that's the best, most accurate procedure. All plugs out, of course, and fully charged battery. You might want to monitor spark strength, which should be a sparkling blue arc, at least 7/16 length. You can easily make a gadget for that, just use your intelligence. For me.......low intelligence......I pounded a couple nails through a piece of dry wood. I control gap with adjusting a small alligator clip. Like to see 3/8 inch jump on pre CDI stuff.

Ok, will try that. I also noticed that oil level is a little above max took off the filling cap that leads right into the block but the oil looks clean and nice, same on the level pin. What happens if the service center filled to much oil?? I also looked in the manual now and oil pressure shall be between 200-270kpa. Mine is 395kpa.

Does it seem to be running rich? The plugs do look a bit dark. What oil are you running?

Yeah they do. IF i remember correct, i believe it was original quicksilver 25W-40
Tomorrow i'll get my compression tester, i hope all is good