My 30 year old but new to me Sparkman and Stephens 34 needs an engine replacement. Despite throwing god money at the old Volvo MD11C, it's finally come to an end. The old Volvo is a 23hp rated engine which powered the boat OK most of the time but I could imagine might struggle a little in tough conditions. It was coupled to the 110s saildrive sitting under the companionway steps - as opposed to many that had the engine further forward over the keel.
The local Beta dealer has suggested the Beta 25 coupled to a SeaProp 60 saildrive, but having read much about similar yachts, it seems that some people would go for an engine with a little more power. Alternative replacements for example would be the 27hp Volvo D1-30 or the 3YM30 29hp Yanmar.
I know Beta does a 30hp engine of course, but the 25hp is considerably lighter. All are much lighter than the old Volvo. There was a Beta 28hp, is that now discontinued. It's not listed at least here in Australia.
S&S34's have a displacement varying between 11 and 13000lbs and a waterline length of 24'5" to 25'3" depending on fitout.
So the questions is, I know the 25hp would do the job but would a 30hp be better. Long distance cruising will be in its future.
As to the prop, I haven't even started thinking about that yet.
Hello and welcome to the forum. My prop calc shows that you need 18 to 20HP to achieve waterline speed so you have been given the correct advice as far as power requirement is concerned. The HP variation comes about with the choice of propellers. Using something like a 3 blade Flexofold the HP requirement is 18HP whereas using a 2 blade folding with a smaller blade area calls for more HP because the 2 blade prop is less efficient than the 3 blade.
The 30 HP engine wont be better as far as performance goes, but if you want to go cruising and have a high output alternator and mabye an engine driven refrigeration compressor, the 30 will be the better choice. It has a larger engine block so it is easier to fit a large alternator. Beta Marine offer a 70 amp alternator as the upgrade on the 25 whereas the upgrade on the 30 is now 120 amp.
The Beta 28 engine is still available in the US but it actually only develops 25HP in the latest edition. This downgrade was made by Kubota to keep the engine compliant with the latest EPA emissions requirements. This engine has more torque than the 25 so is well suited to turning a larger propeller.
I hope that this helps, have fun, Stanley
-- Edited by Stanley on Monday 25th of June 2012 08:40:09 AM
I repowered my S&S34 with the BD722 which is 20HP. works fine. The advantage for me with the Beta was it exactly fitted where the old Volvo MD2 was located without the need to change the engine cover dimensions or mess with the flooring.
