Via Facebook I obtained some photos, from a Ukranian friend, of how a couple of the five Ukranian 110 foot Island class cutters have been rearmed.
The intention was to rearm the ships with the MSI Seahawk 30mm, which reportedly will be the new USN Mk38 Mod4, but apparently it is not yet available, so instead, the ships have been armed with a Soviet era 25mm gun, the 110 PM. As can be seen, control is entirely manual and lacks stabilization, sensors, electro-optics, or any kind of firecontrol computer.
It’s not much, for a Navy facing off the Russian Black Sea Fleet, but at least it essentially restores the capability they had before the transfer. In some respects, it may be superior with a higher rate of fire and a heavier projectile.
Chuck Hill's CG Blog 
This was the original source of the photos. It is in Ukranian. https://www.facebook.com/morskyysvobodivets/posts/603809937517258
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I linked to this page in a comment to a news video, on YouTube, that said the USA had provided ARMED patrol boats to Ukraine…
and what if we had?
Well, in retrospect, it now seems like it should have been obvious to give the vessels to the Ukraine Navy with more powerful and more modern weapons than those carried in USCG service.
I liked knowing, from your blog, that that news service got it wrong. I thought you would like to know that.
Presumably disarming the vessels was standard procedure, several years ago. About fifteen years ago Canada provided 100 surplus armoured vehicles to African Union peacekeepers in South Sudan. Their armament was a puny one man turret with a .30 and .50 machine gun – the same turret as originally used on those big old USMC amphibious vehicles.
When Canada purchased the turrets for those vehicles it agreed the vehicles would have to be disarmed if they were sold to a third country – unless the USA gave explicit permission. The US eventually gave that permission.
The Ukrainians did have plans to improve their armament. The Gun they did have is pretty similar to the way they were armed in USCG service, so leaving the 25mm Mk38 on board would probably have made no difference.
when we first commissioned the 110s we had a 20mm manual weapon, rumor said from ww2. well rumor control central you know how that works, but we used to have to oil the rounds before the entered the weapon. just sayin.
I think this was the original armament:
http://navweaps.com/Weapons/WNUS_20mm_mk16.php
Coast Guard Cutters and Craft 1946-1990 says it was a 20mm/80 so it was not the WWII vintage Oerlikon 20mm.
Not a good gun.