Hi A.~
We also did not have the luxury of a dishwasher for many many years. (When I was in the hospital having our 6th child, my parents bought us one! Although it was a trade off - our tiny 1000 sqft house had only two upper cabinets and two lower cabinets in the kitchen, and I had to give up a lower cabinet to push the washer under the counter.) I had the kids washing dishes as early as 4 yrs old. They thought it was a treat to push the chair up to the sink and have one side full of soapy water and bubbles, and rinse water on the other side. They would play until all the bubbles were gone. They would scoop up the bubbles in the cups and call it a bubble sundae, or pretend to show me 'food creations' that were plates with a stack of bubbles on them. To them, it was a variation on playdoh! Then when the water was getting cold, and the bubbles were flat, they would wash the dishes and cups, rinse them, and put them in the dish drainer. Sometimes if I only had a few items in the sink to wash, they would ask me to toss in a few clean cups and plates so they would have more to 'play with'. Anyway, as they got older, I cut down on the amount of playing, and they just washed, rinsed, and dried the dishes. My first 5 boys were 7 when I expected them to do the dinner dishes, dry them, and put them away. I paired them up so one would wash and one would dry. They had to learn that a family works together as a team, and if they expected me to shop for the meal, prepare and cook it, then they were going to set the table and clean up afterwards. My husband helps wrapping or condensing the leftovers into smaller containers and putting them away. Then he helps with the larger pots, or glass baking dishes, or he helps put away things they can't reach. I usually clean up the younger children/baby and take them to the other room for the evening.
We moved to a bigger house (9 people + their beds, dressers, closet space, rest of the furnature, and a kitchen table to seat us all doesn't fit well in 1000 sqft.) and it came with a dishwasher, but the kids, the ones that are ages 4-up, still wash dishes, pots and pans. I don't use the dishwasher all the time when we have time to do them by hand, and the valuable lesson of teamwork can be reinforced.
Among other things, my 6,9,11,13,& 15 yr old also take turns each night pealing 7 lbs of potatoes, or 2 lbs of carrots. They have to be part of helping to make the evening meal, or taking care of the two youngest while I'm making dinner.
When they act like they don't know how to do something, I just take the time to teach or re-teach them. They are not going to get away with acting like they can't do it, or not do a good job in order to get out of doing it at all. If anything, they have learned that the ones who apparently aren't good at it need the most practice to get it right, and they in turn get more work than the ones who do it well. So once they catch on to that, they all strive to do it well and do it right.
They don't get paid for doing their part in the family, any more than I get paid for washing clothes, cleaning the house, or making the meals.
I know what you're saying about boys developing motor skills later than girls, but I think yours is a case where your son doesn't want to do, and he's holding out and hoping you'll give in and take him off of dish duty. I don't think he's too young at all.
What other jobs does he do aroung the house? and does he do them well?
Like stripping the sheets off the bed for the laundry and putting the clean ones on? or tying up the kitchen trash bag, taking it out to the cans, and coming back in to put a clean bag in the kitchen garbage? or dusting, vaccuming, sweeping the floors? Folding his own laundry? Bringing in groceries and helping to put them away?
Maybe he doesn't understand that this is the beginning of a new time frame in his life where more is expected of him??? I don't know - just throwing out some thought.
Good luck and don't give up!