Engine warm up question

[nightvision]

Hi all,<br />I have a general question on warming up an engine. I have an 2005 I/O, 3.0l,135 hp, Mercruiser Alpha1. Part of my boating procedure is to start the engine on the muff at home for about 3-5 minutes before I leave for the lake. The lake is about 40 minutes away. Let say one hour after I warmed up the engine at home, do I still need to warm it up again for a few minutes before taking off? <br /><br />Thanks.