Tranona
Well-Known Member
I am based in Poole. Appreciate your concern about corrosion - even if I think it is misplaced. Just because your ancient engine suffers from it does not mean it is an issue on new engines - as I said things have moved on. The Beta has a pencil anode because the particular design leaves open the possibility of galvanic action between the stack and housing. Change the anode (easily accessible on the side of the HE) and no problems. The Nanni marinisation of the same basic engine in the lower HP range does not have an anode because of the different construction of the HE, but does in the larger sizes. I have explained the situation with Volvo - no anodes and generally no problems. Not 100% sure about Yanmars latest engines, but older ones I am familiar with do not have anodes in the HE.
As to access for maintenance, that is easy to see from the drawings and specs. Most have all the key points at the top and front of the engine and left hand side looking from the front. Volvo have the filters low down on the LH side which was one of the reasons why I decided not to go Volvo again despite over 20 years good service with 2 engines (plus an unhelpful dealer). The Yanmar you mention also has the oil filter low down on the left hand side - incidentally this is also a common rail engine so given your unfounded aversion to electric fuel pumps would not be on your list!
I am not surprised you get such poor motoring performance given your choice of inappropriate propellers. If you are going to spend the money on a new engine then buy a decent propeller - there are no "benefits" of choosing different propellers for different conditions except perhaps if you do a lot of long distance motor sailing when a variable pitch propeller like a Bruntons may offer some advantage over a fixed pitch (but folding or feathering). My choice was a Featherstream, although a Maxprop would also be on the list. The key benefits of these propellers is that the pitch is adjustable so you can fine tune and you can have a different pitch in forward and reverse - essential with some gearboxes (like Yanmar and TMC) where there can be a big difference between reduction ratios in forward and reverse. As you have space for a folding propeller then a Flexofold would be a good choice.
It really is not difficult to get it right as you don't have to do the hard sums (if it was difficult I could not do it!) as they are done by the computer programme. All you need is the basic data on the boat including the space you have to spin the prop and a ball park engine/box combination to establish the hp required for hull speed. This will give you a starting point, and you can then try different combinations of engines and reduction ratio to achieve the maximum speed at close to maximum revs and the largest propeller that will fit the space. With a feathering or folding propeller there is no drag penalty for a larger diameter. This is exactly the process I followed then checked with Darglow who make the propeller and their calculation was virtually the same as mine. Important to go with the manufacturers recommendation as if it is wrong they will correct.
So, this is what I ended up with. The original engine was a 20hp Lister and a 15" propeller which gave barely 6 knots. The new is a Beta 30 with a 17" propeller which gives 7,4 knots (hull speed is around 7) and cruises comfortably at 5.5 knots at 2200rpm.
Hope you find these ramblings useful