Evolution Marine Shaft System

Well, I wouldn't have guessed that engine. Belt driven timing, balanced engine... They have specifically addressed the inherant lack of balance in a straight four and I know a little lobsterboat with that same engine that does not vibrate much at idle in fact, it appears a well-muffled gas ungine at idle. I will ask today about his mounts but I consider it quite vibratory as the RPMs come up. Hard to find a mount composition that does all things at all speeds. Most reduction gears have no problem with twice the recommended idle of that engine. I like a slow idle, too - less clunk on shift, more relaxed feel. Glad to hear of your experience with Evolution.

[BKay]

I confirmed the mounts are Aquadrive mounts. Similar to the Cushyfloat series recommended by Evolution and much softer that the standard Yanmar provided mounts. As I recall there was about 50 RPM range for idle speed to remain within factory specs. I was at the low end of that range on the tac and advanced it slightly to get vibration to something tolerable. I found a great article on vibration control that gave a good technical description on how to calculate the point that harmonic vibrations occur - but the bottom line was to change your RPM setting as one means of interrupting the vibrations. I'll mess with her a little more when I get her in the water this spring and talk to some tech folks to confirm my tac is reading accurately. I too was unpleasantly suprised to find this much vibration in that particular setup.

To OP, sorry for the hijack. I'll bring in my construction notebook and see if I can answer any of your specific questions on the EMSS. I wish I had access to someone with hands on experience with the system before I made my decision. Since they are a little pricey and I'm kinda cheap, it would have made the decision making a lot less stressful.

[BKay]

The EMSS does use oil - 75-90 Synthetic Gear Oil. The oil is fed from a header tank that uses pressure (1.5 - 4 lbs) so it does not need to be above the thrust bearing. But as a practical matter I've never seen one installed below the highest point in the thrust bearing. Oil is fed to the shaft log from a single 1/4" line - since this is in the keel and runs cool, there is little breakdown of this oil. Nevertheless the guys at Evolution recommend annual changes. This must be drained while the boat is out of the water. However, they told me they have commercial guys go several years without changing this oil becuase of no haulouts. Oil is also circulated from the tank to the thrust bearing and back to the tank using two 3/8" lines. The thrust bearing operates at around 180 degrees so this oil does break down and must be changed. This is the area where Evolution says you can't skimp on the maintenance schedule. However, it is changed in the boat at the header tank and takes longer to type it out than to actually do it. My whole system holds less than about 3 quarts of gear oil.

The EMSS on my 29 footer cost about $4500 more than the cost of a conventional shaft and stuffing box arrangement. It's a pretty slick piece of kit, but I can't say with any confidence know how it performs relative to a conventional system. As I mentioned earlier, if I were to start cutting costs, this would be one of the first things to go on my boat.

My impression of Allan at Evolution is that he's pretty proud of this system and wants buyers to be happy with it. He gets personally involved in selection and ensuring builder has the right installation instructions. He has spent a fair amount of time on the phone with me both before and after purchase to make sure I knew how it worked, materials, and how to maintain it.

[Tigawave]

There is also the Seatorque drive, another oil filled tube with integral roller bearings, thrust bearings and aft oil seals.

They use quicKutter shaft rope/line cutters (we supply them) to protect the seals from monofilament line, they will also cut stainless steel wire traces as they have hardened blades. This combination is used by commercial boats in the Uk as well as makes such as Fleming. Same advantages as people have mentioned. These cutters would also work well on the evolution system and could be retro fitted, although there are some issues if you have a feathering/folding prop.