Heat lightly greased dutch oven over medium-high heat.  Add ham and cook for 3 to 4 minutes or until beginning to brown, stirring occasionally.  Remove from dutch oven and place in large bowl.

Add water to dutch oven and bring to boil.  Add potatoes, return to boil, and continue to boil for 5 minutes or until potatoes are tender.

Meanwhile; in bowl with ham, add mayonnaise, mustard, celery and onion.  Stir until well blended.

Drain potatoes in colandar and run under cold water until cool.  Shake off any excess liquid and add to ham mixture.  Stir gently until well blended.  Add pepper to taste.