calculating correct pot odds

[2Fast2Furious]

I think I'm making mistakes on my pot odds calculations for outs to making a flush. As I understand it, you can guess your percentage of making your flush by multiplying outs by 4 on the turn and 2 on the river, assuming you need one card to hit. So say you hold A [img]/images/graemlins/heart.gif[/img] 8 [img]/images/graemlins/heart.gif[/img] pre-flop and flop comes 4 [img]/images/graemlins/heart.gif[/img] 5 [img]/images/graemlins/heart.gif[/img] 3 [img]/images/graemlins/spade.gif[/img] You've essentially got 9 outs to your nut flush which equals ~ 36% or c. 2.75:1 (this excludes any other outs you think are good, but in this case and A might be bad since it gives a straight draw life, so I exclued any A as an "out"). So if I'm being offered anything better than 2.75-1 on my pot odds I should call (implied odds probably would lower that to 2-1 if I do hit flush correct?)

If a blank comes on the turn I still have those 9 outs, but now it's more like 1/2 the 36% chance so pot would have to be offering me 5-1 essentially to call a big bet.....

Is that right? thx!