First of all - I would like to thank you for The Great Site of Verado engines! I live in Norway and it is a small country compared til USA- and the dealers of Verado are few. It seams like most dealers of boat engines have many different engines brands to work on and therefore not espesially experts in any!
So, I hope I can get some help from you in a matter of my engine!
I bought an 2007-mod Uttern D66 with a Gen1 - nov 2006 225hk Verado this year. With 110h on it. It didn't start very well, because of the Float-level problem. This was repaired and I was very happy with boat and engine. But there was a few issues that I noticed after spending some time with it, the idle was going up and down a couple of hundred rpms. A few times, after driving and then putting it into idle, the engine stopped but was easy to start again. This got better after a while. I startet to notice that "suddently" the engine was making a noice from 1000-3000 rpm, like some kind of resonance. It got worse after some trips. Since the engine didn't had it's 300h maintainance I decided to change sparkplugs and filters. The spark plugs were then black, you can see that on the pictures. I have spent many hours reading in this forum, and you don't like sparkplugs to be black in color....
I am thinking-could this be a couple of issues with my engine. Like is the bearings of supercharger go bad that make the noise? Where do I start to check about the sound-it is not so easy to check while driving.... Is the black spark plugs indicating that I need to push the engine to maks rpm for a long periode of time to burn out some carbon? Like I said I have changed the sparkplugs and the rpm got a little more less up and down, but it is still going up and down a bit. If I put the motor into gear and drives at about e.g. 700rpm it doesn't keep itself at 700rpm, but goes up and down 100 rpm or so. At e.g. 1200 rpm it is very steady.
Where do I start to check things and what should I do?
Gen1-nov 2006 engine. Last owner did not use it in 2010, so it has just been started a few times on idle in 2010 and spring 2011.
Service 100h ok, not done 300h yet. The motor has now 150h, so I have used it for 40h.
Originale prop was destroyed after hitting something "hard" so prev owner changed to a smaller and engine revs to approx 5800rpm at about 40knots.
I have driven it at about 5000-5800rpms at almost all the trips, exept from the first ones because I had to get used til the boat and engine.
Gasoline was old-late 2009-but I have filled up 400liters after that so it should be fresh fuel in the tank and I'm not getting any water-in-filter warnings. In Norway we have 95octain fuel and it is said to be of very good quality. The prosessing plant for gazoline is just 10km from where I live. No one in Norway use Quickleen or other types to mix with the gazoline.
Battery ok-i have checked it the way you recommended it.
Temp water max, 65C/149F
Oil Temp max: 105C/221F
Picture of the spark plug, starting from the top:
Picture of the prop: