Ok I went and picked them up, but am a little confused now. The right side manifold does not say Mercruiser and the casting plugs all say Gil. The left side has Mercruiser in the side of it and also has the casting plugs that say Gil. Whats the deal here? Are these the Gil produced HP500 manifolds?
Also the risers are about 15" long which I believe will be too long. So how do you determine what the right riser length is for your boat?

Read post 7. Most likely the Merc manifold went bad and was replaced by one Gil. Gil made them but supposedly the Merc was different and failure-prone.

ok, thanks Chris I'll keep looking.

My Merc/Gils did crack at the wedge divider. They were 8 years old and had spent the first 200 hours in salt water.

if the risers are 15" long, they may have been for a TRS setup. Or dry all the wayto the tip. With the riser end going thru a boot at the transome.They can be shortened by a competent welding shop or I understand Gil will do it for you also.
I shortened my own and added a downward turn to match my tips.

So as far as riser length goes it's whatever fits between the engine and the transom/tips? I do like the long risers it looks better than the black hose.

Most manufacturers will do whatever you want with the pipes. Some come up into an elbow and mix water in, then go thru rubber to transom tips. Some go all the way out. What complicates things when looking at used exhaust is that different setups use different tails. For example, on the Gil you can get Bravo tails and you can get TRS tails. Since the TRS is longer, their pipes are too.

Ok what are tails and what are the difference between bravo and TRS tails.
It seems I really opened a can of worms here and I apologize for the 20 questions, but before I spend money I need to educate myself.
All I really want to do is get some good used manifolds with some stainless risers to angle cut short tips.
Am I making this more complicated than I need to?

Here is what I bought, TRS risers. Thesecond pics is what I changed them to, Bravo risers. The tails would be any pipes you need for getting the exhaust to the transome tips, or thru the transome, third pic.

note wedges ... long tails .... water exits end of pipes ...m