MD7a replacement advice

[nickdick]

A popular thread I know, but when it`s finally your time to replace your OWN engine you just want to get it right.

I`ve got and Oyster 26 with a dead 13.5 HP MD7a with a 11 year old Volvo 110s saildrive and 14x8 folding prop of the same age pushing the 2900kg fin keeled boat typically at 6.0 knots in flat conditions when she`s very clean.

I obviously want to do the same with the next engine, and I`m leaning towards a Beta at the moment (ease of fitting & retention of saildrive)

The potential installer (A D Marine Services at Hayling Island) suggest using the Beta 10 (10HP) rather than the Beta 14 (13.5) HP.

My point is; how do I size the engine to give me roughly what I`m used to, or just a little less power? After all I can`t believe that my old MD7a has been delivering 13.5 HP for a while now.

 

[Talulah]

Chrissie on these forums re-engined her Contessa 26 with a Beta 10.
Could be worth sending her a PM to see how she is getting along with it.

 

[Maxi84]

Nick
I have just re-engined my 1978 Maxi84 which had a MD7A/SD110 combo. As far as I can tell it was the original engine and although it ran quietly and smoothly with no obvious health issues other than a small drip from the diesel pump, it would only manage a sustained 3 knots or so at 3/4 throttle and 4 knots at full throttle for a couple of minutes before the low oil pressure warning came on despite there being plenty of oil in the engine. I was convinced that the engine was not producing the advertised power (13hp) either.

The new engine is a Yanmar 2YM15 and matching saildrive with the same 13hp output as the MD7A. In sheltered non-tidal water, running cross-wind I achieved 6.7 knots this weekend. This is pretty close to the expected hull speed (6.5 knots for a 7.2m LWL hull) so it would be pointless in going any bigger. Going smaller would very likely involve losing speed.

I must admit I have been impressed with the neatness of the installation and the layout of the new engine. The water pump and fuel filters are for example at the front and easily accessible instead of round the back and requiring to be a contortionist to get to.

I would recommend Stavanger Batsenter however whatever you have heard about Norway being expensive is an understatement and it is not exactly convenient for you either.

 

[Tranona]

Go for the 14. Exactly the same physical size etc, but higher spec, better alternator etc. The only possible downside is that the saildrive units they use are not widely used elsewhere and Volvo and Yanmar have definite advantages as they supply matched units of their own manufacture.