Hello
Sorry for using English. Stevie - feel free to translate this. I have navigated through Ardnacrusha to Limerick many times. It is easy to do and safe if you go at the right time in the riight conditions. Normally during summer Ardnacrusha run zero or only one turbine, so the flow is normally ok even for single engined boats during summer. However this year in Ireland we had "freak" rain fall all summer and unusually Ardnacrusha were running 4 turbines for much of July and August. This is not normal. Therefore navigating to Limerick was difficult and only possible early in the mornings because there was only one turbine running. Limerick is tidal so you must check the time of High Tide so that you can fit under the bridges.
Normally the Limerick navigation is wonderful and going through Ardnacrusha in a boat is an amazing experience. It is the best kept secret in Ireland's waterways.
1. Only go down to Limerick if ZERO or ONE turbine is running. Only very experienced skippers in twin engined boats should go down if 2 turbines are running. Never with 3 or 4 turbines. The current is too much to steer down the Abbey River under the bridges.
2. Check the times of HW Limerick (High Water) for airdraft under the bridges. You must be 100% sure you will easily fit under because if there is fast flow you may not be able to stop.
3. Always request assistance from Pat Lysaght of Waterways Ireland who will act as a pilot for you and guide you safely to Limerick. He will check airdraft guages for you and advise on the flow. He comes up to Ardnacrusha in his small boat and will guide you down if asked.
4. If coming upstearm in a powerful boat and you have much experience of Limerick navigation it may be possible for safe passage with 2 or 3 turbines running - BUT not recommended. This is because you are pushing against the flow. Better to do this 1 hour before HW as the flooding tide will slow the current a little.
During winter months of high rain fall when 4 turbines are running, and a spring tide is ebbing down the Abbey river the current can reach 12kts at Georges Quay. There can be a 1 meter step in the water under Mathew bridge. A single engine boat would be going backwards.
This may sound scary, but normally during summer the Abbey river is very tame because of slow current and it is very pleasant. We have gone down many times in both single engine and twin engine boats with no problem. This August I had to come upstream from Limerick with all 4 turbines running. It was hard work and I would not do it again.
Here is a warning I posted on CPB earlier this month.
http://www.powerboat.ie/forums/showthread.php?t=1973The reasons boats have were damaged in Limerick this summer and at Killaloe bridge are:
1. Inexperienced boaters were not used to fast flow
2. Boaters did not ring ESB to check how many turbines were running
3. Boaters ignored advice or did not ask Pat Lysaght for assistance
There is a feasability study being done to reopen the old navigation from Killaloe down to Limerick using the old course of the Shannon and the disused Limerick canal system. This would be safe for all boats at all times.

Some usefull links about Ardnacrusha and Limerick
http://www.powerboat.ie/forums/showpost.php?p=14554&postcount=5http://www.powerboat.ie/forums/showpost.php?p=13362&postcount=1http://www.powerboat.ie/forums/showpost.php?p=13672&postcount=9Hope this was of interest.
Noel