Henry, I'm glad you chimed in to this topic. It has been on my list for some time and I am still not comfortable as to the best approach.
I have studied the cooling diagrams and I see substantial differences between the closed cooling (CC) and raw water (RW) systems.
For starts, the thermostats are on opposite sides of the engine. In the RW system: water comes in, splits into the feed to the PRVs on the risers and the rest is immediately redirected to the logs by the recirculating pump and after the logs goes into the block.
By contrast, the CC system takes water in, goes to PRVs, to the heat exchanger, the thermostat, the engine block, and finally to the logs at the end of the cycle. Not an insignificant difference between the two systems.
So if one adds a heat exchanger, where should it go? before the cycle as in the CC system? After the cycle as in RW? Does it matter? Should the thermostat be relocated front to back? Can a Chris Craft Closed Cooling thermostat housing be sourced at reasonable cost?
The Chris Craft heat exchanger has one port in and six out. I have not seen an aftermarket heat exchanger with that configuration, if one where to try to replicate the Chris Craft closed cooling.
I have spoken with suppliers of "cooling kits" and got very tentative "wishy-washy" responses. My mechanic who is good at marine engines does not want to get into the subject. So given the expense and possibility to mess things up I am a bit cautious, reason why I started this thread to find out if there are ANY outdrives with closed cooling out there.
Given the lack of positive response, I conclude there are NO outdrives with closed cooling. Chris Craft does not seem to have offered the option for outdrives...
...And this bears some reason. What the inboard people on this forum may not realize is that a Q engine sits extremely close to the transom. The outdrive's steering tiller swings in between the risers and there would be NO room for the thermostat housing, associated plumbing, and never mind a heat exchanger, between the risers, the tiller and the transom as Chris Craft has it in their own Closed Cooling system. The picture below of my engine shows how tight things are.
Chris Craft possibly did not want to have yet another cooling system for the Q with outdrive configuration, so outdrive boats were produced with the standard Q raw water system only. My theory, I would love to be proved wrong.
Henry, if you want to email me ( pitjean1"at"gmail.com ) we can share other ideas on this.. Thanks.