Lets take Horatio Nelson and transport him back in time to the Anglo-Dutch Wars of the 17th century. Nelson will face off against famed Dutch admiral Michiel de Ruyter. Who will win? 
True, besides that it is basicly a populairity contest between the Netherlands and Britain (which Britiain probably wins).This goes into the ASB subforum.
This goes into the ASB subforum.
This goes into the ASB subforum.
While I voted Nelson the reality is the battle would be determined as much, if not more so, by the quality of the officers and crews rather than the Admiral's tactical abilities.
And that's where Nelson has a serious chance of falling down. Simply put, the Anglo-Dutch wars largelly predate the increasing 'professionalisation' of the RN officer corp... the navy list and testing for promotions up the ranks between Midshipman and Captain only really developed following the early disasters of the 2nd Anglo-Dutch war.
At the same time during the 17th century it was standard for the fleet to stand up for the campaigning season then be laid up for winter; unlike in Nelson's era when it was capable of maintianing blockading squadrons active for years and at sea for months at a time. This in turn has implications on the level of experiance and the performance of the crews... look at the difference in performance between the British (at sea most of the time) and French (largelly blockaded in port) sailors during the Napoleonic wars by way of example.
So, Nelson with late 18th century officers and sailor, even with 17th century ships will kick arse. Nelson with what's at hand in the 1660-80s would be fighting on a much more level playing field, and so has every chance of having one of his underlings f*** things up.
the dutch guy is before my period of interest, so I don't know him, but...
With a competent foe, do his tactics work so well? Or, have him born at an earlier time. Does he still develop what would be advanced tactics? Is it his mind that you want time transported, or his tactics?
I'm not very knowledgable about naval warfare.
However, looking at the three most important naval battles of Michiel de Ruyter and Trafalgar, which is all I know about Nelson, Michiel was more outnumbered than Nelson was in his battles (which I gave a cursory glance, might have missed a few) and still won all three of them, so I'm inclined to give Ruyter the benefit of the doubt.
http://en.wikipedia.org/wiki/Battle_of_Solebay
http://en.wikipedia.org/wiki/Battle_of_Schooneveld
http://en.wikipedia.org/wiki/Battle_of_Texel