That's okay since no post should be considered long winded when important information is needed to try and help with some sort of a resolution...The more info the better.
In most cases with later model boats like yours you could try locating the original engine model by using the boats hull identification number and calling the boat manufacturer to see if they have a record of the build sheet that might be able to help ID the engine model from new. Four-Winns is pretty good with keeping record. I also believe you might be able to get some basic info using your hull ID number looking up boat parts online from F - W....
http://parts.fwdealer.com/
^ They may be able to tell you about the horn location as well.
With Volvo it's a 50/50 of where the horn could be... In the early years the horn was more communally found on the engine like your other boat had. As the years went on it was slowly moved up to the helm area so it could be heard better. In 2000 it could be either or.
On your old boat, like you mentioned it was on the engine like seen here,
http://www.volvopentastore.com/10-Pi...view_id.790283
On your new 2011 engine it requires a horn to be mounted at the helm area that looks like item number 16,
http://www.volvopentastore.com/Engin...view_id.783773
If you need a good photo of the horn that goes under the helm area, search the part number online under "images" and you should be able to see it...You may even see a place where it's mounted on a boat under the helm to help give you a better idea...Was thinking of this photo as an idea
http://www.bing.com/images/search?q...d44b503521b4a8b5d5cd623bf027ac72o0&ajaxhist=0
If the old engine had a horn mounted on the engine then there's a chance that one was never mounted under the helm area for the new engine.
To test for a horn, try finding one of the engine water temp switches, turn the key to on/run (engine not running) and using a jumper wire connected to ground, touch the temp switch wire and see if the horn sounds.
