Upping Distance Sprint to Oly. How long will it take?

That's hard if not impossible to say without knowing your training miles. The training log feature of BT is wonderful. Try it. When you have a question like this, the experts (not me) can look at your logs and give you an educated guess.My first Olympic was harder than I thought. Pacing makes a huge difference.

your run is definitely fine, since you are training for a marathon - like the above poster said without knowing how much you are swimming and biking tough to say.

I ended up last season (my first) changing Chicago from sprint to olympic, but my training level even for the sprints was olympic distance time/distance of training so I was encouraged by all around me to do it.....

Thanks for advice. I am still only doing sprint cycle and swim miles. only really started thinking about this in last few days. coming close to end of the season in ireland and just thought it might be something I'd like to do. May well still give it a go as i am a bit stubborn about this sort of thing. once i get something in my head cant really back out.

any more advice would be gratefully received

Ray 

The biggest difference between a sprint compared to an OLY is the relative swim distance. The 1.5K (.93 mile) swim takes some signifiant effort and could be trouble if you are not prepared for it. You can adjust the effort for the bike if needed to finish the bike leg even if you have under trained to go the 40K (24.9 miles). The 10K run should not be any problem since you are already training for a marathon later this year.

General fitness does not translate directly to swimming. It takes actual practice using good technique to move up to an OLY distance. Unless you feel comfortable swimming the 1.5K distance you may not even get to the bike or run part of the OLY tri. Only you know if you are ready for the swim.

Good luck if you go for it.