What do you mean 13 hp rated engine is 13 hp surely not 11 ponies as you put it?So what you are saying in effect is all 13 hp driven 21 lpm washers that have been sold or still being advertised by suppliers don't or can't run at 21 lpm?
Hi I have sealed a number of drives over the past few years along with using the smartseal products along with many others.The smartseal products are ok but not neccessarily worth the upilift in price I now tend to agree with the other posters though and try to avoid sealing if possible,. I normally inform the customer that they will need their drive done again in around 2/3 years if unsealed but if sealed it will still need doing again in 4/5 years and will also require resealing. When they see the difference in price they generally are happy just to clean and sand. Whatever you do, do not seal clay pavior drives !!