What did I do on my boat today? Changed the impeller in my Bukh 10 HP diesel. It seems simple;
1 Remove four screws holding the cover plate
2 Remove cover plate
3 Pull out old impeller
4 Push in new impeller
5 Replace cover plate
6 Replace four screws.
Allow about 2 hours.
1 About 15 minutes finding that the cover plate is down the right hand side in a location that is accessible by one hand only, becoming invisible when hand is at the plate
2 About 15 minutes finding the shortest Philips head screw driver you have and engaging it onto the four screws without being able to see said screws. Add additional time for hot conditions in which your hands become covered with sweat and oil such that everything, screw drivers, screws etc, slips out of your hands into the bilge (I have an old paint tray under the engine, which catches dripping oil and dropped screws nicely)
3 About 5 minutes pulling the old impeller out with thin-nosed pliers, and using the same pliers to put the new one in.
4 About 5 minutes getting some Butyl off the roll to put around the edge of the cover to form a new seal.
This is when the fun really starts
5 About an hour and a half trying to replace the cover and its four screws. Rookie mistake Number 1 - thinking that the screw holes are placed symmetrically around the plate (they are not). Rookie mistake Number 2 - thinking that you can use the writing on the plate to orient the "up" side of the round plate (in the correct orientation, the writing is rotated 90 degrees anti-clockwise). Use choice language when the first two screws go in, but the remainder obstinately refuse to engage into the (wrong location for the) screw hole and regularly drop into paint tray off the end of your screw driver which, of course, you can't actually see. Being stainless, the screws are not magnetic so they don't stick to the end of the screwdriver, but I found a small blob of butyl helped keep them on the end of the screw driver as I poked around blindly trying to find the screw holes.
6 Finally find the right orientation and get the screws in. Promise yourself to buy a decent Phillips head screw driver, and throw out the useless cheap lump with worn flukes that you bought from the Big Green Hardware Store.
7 Decide to clean the water intake filter. My boat has an "Osculum" filter (I think its latin for "kiss"). Get it apart but don't realise that you have to ensure the seal is good when you put it back together again, so that the impeller can suck the water through it. (Yes, I know there is no such thing as "suction" force, so don't flame me here). Turn over engine and witness a disappointing dribble of water and small clouds of steam at the exhaust. Turn off engine.
8 Get a hose and flush out the intake stop-cock with the jet, getting wet in the process. Mop out resulting puddles and find two old cigarette filters that could have been jammed in the pipes. Clean boat grime off Osculum cover and gasket and look admiringly at how transparent the cover has become (you can actually see inside, now)
9 Fire up the engine and stare in wonder, for a gratuitous number of minutes, at the free flow of water through the exhaust.
10 Pack up and go home to a long shower and a glass of Tempranillo (or two).
The photo shows the replaced cover. The wire dangling in front is not fixed and I don't know what it does, apart from partially obscuring the fourth screw.
(PS Maybe the wire attaches to the bare lug in the photo - I had not seen the lug until I looked closely at the photo. Heaven only knows how the engine has been running up to now).