Re: AQ170 Carb issues
Same was Roger, haven't heard of any replacement carbs. The carbs aren't really hard to clean and rebuild but be careful with them since it's almost impossible to find new replacement parts. Don't know if Volvo even makes rebuild kits for them anymore but you can find the aftermarket ones on ebay at a reasonable price. Just be aware that the aftermarket kits don't contain new floats, inlet screen, or screws.
Not sure if Volvo still makes the kits or not either. Found some kicking around the interweb for stupid prices.
Volvo Penta P/N 856470 is the gasket kit, and is just that, a gasket kit. No hard parts for rebuild. Cheapest I found was $23.95 (didn't look too hard), and you would need to multiply that by 3.
Volvo Penta P/N 856471 is a carburetor repair kit that comes with the brass parts and a float (no gaskets). People want decent money for 1 kit, never mind the 3 that the OP needs.
Volvo Penta P/N 856472 is a repair kit with the accelerator pump diaphragm and operating rod (no float, no gaskets), again big money.
I got away with taking mine apart, carefully inspecting everything, cleaning the garbage out of them, then using the Sierra carb kits. Floats are original, and looked OK. Has been running like a top since then.