The ballast pumps are slow but can be upgraded fairly easy. That engine is known to vapor lock on really hot days, but all it take to fix it is pour cold water on the fuel filter.
BUT with that said
I have the same engine in my 06 24V and in 6 years mine as only vapor locked once and that was on a 100+ day in a heated lake with a power plant. I took a bottle of water and poured it on the fuel filter and it fired it right up and ran fine the rest of the day.
That engine also get my pig of a boat on plan with 3300# of ballast with no problem with an up graded prop. So in a 21V it would be even better.
Here is how to up grade the ballast. I did it on my boat.
http://www.supraboats.com/bbs/showth...pgrade-project