Understanding tides for boat launch from marina

[9greej10]

Hi All

I finally took delivery of my Seapro inflatable with 20hp engine and I am looking to take the family out on it for our firs trip in September. Whilst I could launch from the beach (I have launch wheels) I have decided to launch from a slipway in a marina for ease. However, the marina is tidal and they have send me the following info as I need to allow enough time either side of high tide to launch and recovery the boat. Please could someone explain exactly what this means in terms of what time I can launch the boat and and when we would have to be back to recover the boat at the marina:

18th September – high water is at 10.49 and 2306 – 1.7 metres over the sill

Many thanks

[Tyger]

Obviously high water ( tide in) is at 10.49. The rest I'm assuming is that the marina if its like a couple here has a barrier across the entrance to keep a minimum water level in the Mariana to stop it emptying at low water. So at high water you have 1.7 meters clearance over the barrier / sill, at low water you cant get into the Marina .
Dont hold me to that, but thats how I would understand it.

[sonny1]

every slipway is different . if at all possible i would suggest you hang about at your chosen slipway and observe other people launching and try to start up a chat . explain you are new and im sure other boaters will be only to happy to explain what they are doing and why . also ask about local conditions and what to watch out for ... good luck and enjoy it , launch and recovery is part of the fun

[harrison]

Some help but not enough info from the Marina to work out times for adequate water depth over the sill.

If you know the tidal range (high and low water depths) on the day and depth over sill at hw then you can approximate water levels at any given time in between using the ‘rule of twelfths’

“During the first hour, the water level rises by 1/12th of the total tidal range. In the second hour, it rises by an additional 2/12ths of the total. During the third and fourth hour, it rises by 3/12ths. Then the increase begins to slow down. In the fifth hour, the water only rises by 2/12ths, and in the sixth hour it rises by 1/12th. The pattern is 1,2,3,3,2,1.“

Bear in mind it’s only an approximation and for more accurate predictions you’d really need to use the tidal curve on the chart for that area.

All this is a bit over the top, and as @sonny1 suggested, just have a chat with the locals, they’ll know. You won’t need much depth over the sill for a sib, but reckon I’d be looking at 60cm minimum for peace of mind and a bit of leeway.

[9greej10]

Great - thanks everyone for your help.
Looking at the timetable they have given me I think I can launch the boat at 9am and then recover at 12.30pm as that's essentially 2 hours either side of high tide. 3 hours is probably enough for the first outing on the boat anyway!

[sonny1]

hi @9greej10 , let us know how you get on and some pictures are always good

[9greej10]

Will do

Does anyone have any tips re: anything I should do after the trip before the engine is stored away for a long period of time? Someone mentioned draining the engine before a long period in storage without use? also draining the fuel nose if its being left for a while? The engine will be stored upright in my shed but any tips/gotchas I should be aware of will be greatly appreciated! thanks again!

[CRF999]

My routine after sea water use, and not planning using for a week or two , is.

Good fresh water wash all over, particularly under the power head.
run the engine to flush it out in a suitable container of fresh water for AT LEAST 5 min ideally 10.
Take out of container and let it drain for at least a further 10 min.
With kill cord removed pull it over slowly to turn over the pump and release any trapped water.
oil or grease any moving parts and exercise.

For over winter I would also drain all fuel from carb and onboard tanks.
Or you can run the fuel out until the engine stops whilst flushing it out.

Check it a few weeks later for any signs of remaining salt and deal with it.

Some may fog the engine. I choose not to.

Regards Clive

[9greej10]

Fantastic - thanks for the info Clive.
To drain the carb of fuel do I literally detach the fuel hose from the engine and let it run dry until the engine stops? Thanks again!

[CRF999]

Either drain it manually or just turn the fuel tap off and let it run dry.

I find run dry to be cleaner and easier. If done as part of the flushing operation its a doddle.

Clive