The first thing you need to do is remove all exposed sillycone.  The next is sand out any chips, dings and whatevers.  Then start sanding the whole pump with 220 grit, make it smooth and nice to the touch.  The next thing is to get some paint, you have a couple choices. 

One, you can spend a bunch of money and get two or three part automotive paint, a spray gun and an air compressor (if you don't have one now). 

Two, you can get some Duplicolor Ceramic engine paint, the only draw back with this paint is after the first hour you can not recoat, you have a five day waiting period. 

Third, you can get some Duplicolor Truck & Van paint, Pure White/Linen White, this is the exact same color as the Place Diverter powder coating white.  Spray it with white Duplicolor Primer, sand with 320 or 400, then clean thoroughly and then paint.  After it is all painted and dried for a minimum of one day, light sanding, recoat with white to fix any minor imperfections and then spray it with Duplicolor Truck & Van Clear.  you will have to put about five light coats of clear to get the appropriate finish and look.

Good Luck !  If you have any questions give me a call after 6pm.

Jim

cant see it under the water any way

i think i would try paint stripper first, wire wheel will leave deep marks and you will be sanding forever

jim, prior in thread you say that ceramic white works well but takes days of drying, what primer and sanding do you need and which clearcoat was used and did you sand prior to each clear and i cant find the thread which shows your paint work with installed engine.

i think i would try paint stripper first, wire wheel will leave deep marks and you will be sanding forever

If you must use power tools, a duel action sander, quick and easy.