Stopping marine growth on the skeg and lower gearbox of an outboard

N

nigelstgeorge

Well-Known Member
Joined
13 May 2007
Messages
124
Location
France
www.iledere-france.com
We have a RHEA 23 with a 150 HP Outboard. Sadly the engine will not completely lift clear of the water when moored and the bottom skeg and lower gearbox are submerged. This means weed and algae growth which is a pain to scrape off. We have tried with limited success putting a large blue IKEA bag over the lower unit and this helped but the bag is disintegrating and I suspect being blue not keep the UVA completely out.

Ideas so far range from a totally impracticable put a large lorry inner tube between the engine leg and boat and inflate to lift the rear our of the water to large plastic dustbins. Also suggested putting swimming pool anti algae tablets in the bag. (Various aluminium primers and antifoul have been suggested by the boat distributer's engineers are really anti this.) I have thought of maybe something like a large black dry sac but the 50 litre one I have is not wide enough to test.

Whatever, if put over the lower leg there will always seawater trapped but maybe without sunlight getting to the water and leg growth will be minimised.

Anybody got a view on this or an idea that is practical ie easy to deploy. Many thanks.
 
Paint it with International Trilux which is formulated for use on aluminium and is commonly used on outdrive legs.
 
Like nigelstgeorge my first thought was some sort of trunking, but very tricky to organise.

I've seen sizeable Rib's ' afloat dry ' on apparently specially made rafts with a vee for the hull, I'm not sure of the process to arrive in that situation or get out of it - either a lot of throttle or some sort of buoyancy adjustment, the former looked more likely - or the supplier as I'm not a mobo-er, but the end result is boat inc large outboard out of the water, a floating dock - maybe someone on the mobo forum will know what I'm on about ?

Edit; I've seen Rib's raised on rubber sponsons at East Cowes Marina, but at Emsworth Marina there's a Rib completely high and dry on what looks like a plastic raft - neither look particularly cheap solutions but I'm sure they'd work better than Trilux, unless upended in an exposed harbour...
 
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I have pondered this question myself. Weed needs light so if you exclude light it won't grow, however excluding light completely will be very difficult, and only a small amount of light is needed. Weed can grow with the low light available in our waters at up to 30 metres.
 
Saw a lot of dayboats in a French Marina had all seemed to have raised their engines, then put a large plastic trug-like thing over the leg, then lowered again. This, I think, was then filled with fresh water.
 
Firstly as said paint the area with a/f paint made for ali. Then if necessary attach a bag around the leg. The bag will concentrate the a/f to keep growth at bay. Or alternatively just put a bag around the leg and add a bit of pool chlorine type chemical.
Re floats for mobos. One guy at our club uses a float with long plastic cylinders which can be flooded to accept the boat then water pumped out compressed air in to raise the whole boat above the water. Used as an alternative to a/f.
Our club rescue boats one a 6m RIB and one a 5m ali centre cockpit. They are kept on floats consisting of a series of about 30cm cube plastic boxes. With a keel groove up the centre. The o/b leg is raised after boat is stowed. The o/b leg when down hits the float so boat can not go further forward. It is alarming at first putting these boats on the floats. You have to line the boat up square with the float with o/b in straight ahead. Usually going forward slowly. You then open up the throttle, the bow rears up often not straight then drops into the slot. You need then to hold power on while a helper attaches a bow winch. It can be quite alarming to watch even more so to be driving but it has been in use for quite a few years now without mishap. Departure involves lowering and starting the motor. Disconnect the bow attach then with some rocking and lots of wellie in reverse she slides off. Certainly a lot easier than stowage on a trailer. olewill
 
It's a bit unusual that you can't get an outboard tilted enough to get everything but the bottom of the skeg out of the water. Is this because of the transom design or is the tilt limit switch stopping it too soon? Either way, the most practical solution is anti-foul or an alternative such as aqua-cote. be careful with buckets dosed with chlorine as you are adding an oxidiser which will accelerate corrosion.
 
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