Re: 2004 42 mariner/ 2007 SS
Running diesel or gas will have to be a decision based on your personal abilities and the way you use your boat. I can only give you my reasonings for going gasoline, but see how my determination affects your vessel choice.
Usage - Frequent use (2-3 times per week) or hard use, such as a fishing charter, tow boat, or long distant cruiser = go diesel. Diesel engines are work horses and don't require the frequent maintenance that a gas engine does. Good fuel (which equals clean injectors) and better filters are the main points. Oil is in greater quantity and is more expensive.
I use mine on weekends, closer to home with trips averaging 10 miles (round trip). Once a year gets a 250 mile trip with the return trip 4 months later. Oil changes once a year and fuel/oil filter go with it. i also do water impellors at the same time.
Cost - Diesel engines are more expensive to purchase and maintain, but will last longer than gas engines. A replacement long block diesel is 10-15,000 dollars where a gas engine is a third of that. However, properly maintained, a diesel engine sees 15,000 hours before major overhaul where a gas engine might get 2-3,000 hours under it. There are always exceptions, of course.
Maintenance - I don't know crap about a diesel engine, but I can work on most parts of a gas engine as it is essentially an automotive engine. However, the diesel tends to last a little longer and isn't nearly as fickle as a gas engine. Parts are cheaper for the gas engines, but diesels are pretty bullet proof. Diesels also seem to be quieter and cleaner, but some of that is maintenance as well.
Your purchase is going to depend on your needs and use. Either way, have fun with it.
