rustoleum paint is not that expensive and last a long time.you should use a hardner,such as valspar from tractor supply.this makes the paint hard as a rock.i have done a few boats and motors and never had a problem with it.sand it all down,use the etching primer ans spray or roll on.
paint
Final WET Sanding with 180 Grit
Wash Down with 50/50 mix of White Vinegar and Water.
Prime with Rustoleum Self Etching Primer
Paint with Rustoleum Professional Oil Based Paint using the following formula.
1 qt paint
1/2 cup Acetone
2 oz Valspar Acrylic Enamel Hardener (Sold @ Tractor Supply)
Applied using the Roll n' Roll Method. (If Spraying thin with 2 Cups of Acetone and use HVLP Gun with 1.8mm Tip)