2003 225 HPDI running rich ?

So Im boat shopping and just got off the phone with a seller. He has a 2003 HPDI on his Champion for sale and says it prolly needs a "tuneup" Last time he ran it 3 weeks ago he said it smelled like it was running rich and was a lil sluggish out of the hole. But once he got it on plane it was fine for two 6 mile runs. He hasnt run it since cuz he actually has another bassboat he just bought which he said was a deal he couldnt pass up on a Ranger which is why he's selling his Champion.

I do appreciate his honesty but it's got me thinkin what could be wrong with it. Dont wanna make a huge mistake, tryin to learn as much as i can before i make a drive from Virginia to Alabama. What are the pros and cons of this motor in general and what could be going on with it ? Will a compression test be good enough to know if it's healthy or not ? Maybe a timing issue ? I dont know alot bout outboards , have some experience with engines in cars but even that is limited to basic wrench turning i have done here and there. help please http://www.bassboatcentral.com/smileys/sweating.gif