You promise? OK, here's the photo. The blue and red valves are a ballcock a PO put in to keep from having to crank the gate valve every time he wanted to use the motor (yes, I know, and the gate valve turns very easily but is awkwardly placed and takes a while to open and close), and the ballcock I added for the convenience of having a simple way to provide alternative coolant from a bucket or wherever (there's a garden hose fitting on the end of that valve).
Ok, I promise, and will keep it specifically to the seacock system..
Honestly I could care less about the dirt but that seacock configuration is about the most manifestly unsafe one I've seen in a long time! Even if that were a bronze or Marelon, flanged seacock I would still feel uncomfortable with the height and sheer length and the miscellany of nipples and valves that create the hard lever you have working against that seacock.
The raw height of the combination of fittings combined with the non-Marelon gate valve makes this totally scary. Marelon, Bronze or stainless but NOT nylon, PVC or acetal. Seacocks designed to meet UL1121 & ABYC must be able to withstand a 500 pound static load at the inner most hard fitting. Yours is nearly 12" high, guessing here, before it even makes a right ancgle and continues and may not even withstand 20 pounds of force before snapping that plastic, most likely PVC, valve...
I would guess that you do have a bronze flush mount thru-hull based on the lock nut in contact with the well weathered, apossibly saturated and potentially punky backing plate. You may be able to thread that contraption off and replace it with a bronze UL marine rated ball valve but you may also break the seal and need to re do the whole thing. If it is a recessed flush mount thru-hull be VERY careful removing and re-bedding it as many of the companies that made them are now long gone and replacement sizes are not always the same..
Please do yourself a favor and fix this as soon as possible and shorten your overall hard piping height and length.. Whenever possible the last hard fitting on the inside of a seacock should be a pipe to hose adapter. No nipples, tees or multiple valves etc. etc.. You want to get to soft piping as soon as possible to reduce the lever effect on the valve.
It also appears you have a venerable corrosion cocktail with what looks to be a mix of brass, bronze and non UL marine rated ball valves of questionable metalurgic makup. All metals in a seacock system should be galvanically compatible. Yellow brass nipples and bronze elbows are not very well suited for each other, when mixed together, in this environment. I have seen home ceneter brass valves corroded away in less than a years time yet the bronze thru-hulls they were connected to were still perfectly fine..
P.S. NEVER connect a pressurized garden hose directly to that fitting!! It is ok to let the motor suck from a bucket but not ok to pressure feed it. That is if you don't want a motor full of water...