Staying more than 6 months on a turist visa

[tocanada67]

I' m here in Canada from the beginning of January and I plan to stay till the end of april , then I was planning to come back to Canada for other 3 months next winter . It' s all in the two turists visas the one I have now and the one I will have in October .
My doubt is : I will be staying more than 6 months in Canada during 2011 , is that OK ? Can that be a problem if I decide in the future to apply for immigration ?
Is there a number I can call to ask this question ?
Any help is very welcome