SD50 Drive Legs
26 October 2007 | Grenada Marine
The Yanmar diesel is an impressive piece of gear. I have been very happy with mine and I have found few folks who don't speak highly, if not reverently, of them. The Yanmar Saildrive is not quite of the same status.
Perhaps it is just my perception, but Saildrives in general seem to need a little more polish to achieve the levels of reliability and low maintenance of the diesels they are attached to. Among the lot the SD50 seem to be some of the better out there. Ours have served us well so far but there are a few distinct issues that seem to be universal which I thought I would try to address during our annual service session in the yard.
The first thing that seems a little under engineered is the rubber flap that is designed to streamline the hull area around the cut out that the drive leg comes through. Many factories simply glue this to the hull. In my experience this is fine for about one good passage or perhaps a month of hops. I can't recall seeing it any other way than as pictured here, hanging on the leg.
Some outfits make their boats with a bracket that screws the flap onto the hull. This seems like the only durable way to keep it on. So I was faced with a choice, just get rid of them, or come up with a bracket of some sort. Apparently this issue is common enough that Granada Marine has fiberglass brackets premade. I decided to go with the brackets. Time will tell if this was the right choice.
The rubber flaps cover a rectangular hole in the boats hull. The top bezel of the drive leg is circular. If the Yanmar template was circular the existing flap and bell housing attachments would still cover the area perfectly but you could drop the leg down from under the boat rather than toting it through the interior. Per previous blog, a friend rounded out this area to allow the leg to come straight down and it made installing the drive leg (which we hauled out from above) quite easy.
I talk to the factory about this and they did not seem completely comfortable with the modification. I am going to try to get a hold of Yanmar to see if there is any real practical reason not to make the rather small circular expansion in the center of the existing rectangle's sides. I have decided to leave things as is unless I need to pull the drive legs. If I get the green light from Yanmar and need to pull the legs I think I will do so from below with a marginally widened opening.
I changed the zincs out on our drives. I had considered going with the two part kit but several factors changed my mind. First and foremost was the fact that our Varifold props were so easy to remove; three hex nuts to remove the blade bumper, three more to free the hinge pins and one big nut on the shaft and she's loose. Add to those fasteners the blade bumper, the three blades and their pins and the hub and you have everything in hand. Given the fact that the one piece zincs are cheaper and easier to come by and may make better contact with the drive leg I decided to stick with the one part zincs.
The existing zincs both had more than 50% of their material but not by much. I believe that the zincs were stock and if so they lasted almost two years. They did not wear completely evenly which I found interesting. More interesting however was the fact that the factory paint seems to have completely pitted out in some small shallow patches where it looks like aluminum was exposed and gnawed at a bit. Someone suggested that the last haul out paint shop used copper paint. I find that hard to believe (copper paint on an aluminum drive leg?!?) but who knows.
I was going to have the yard do the drive legs with the bottom paint but seeing as how there was still no activity at the end of week one I decided I'd better start knocking bottom prep items off myself. I used an Interlux solution to get things in shape. If this fairs no better by our next haul out I'll have the drive legs pulled and stripped so that I can do a complete set of coatings from scratch.
This time around I used an Interlux solvent to strip most of the nasty bits down to the metal or factory paint at least, and then sanded things clean with 80 grit. There was still a bit of factory paint on the legs but it looked fair and free of aftermarket stuff. I then used the Interlux etcher (a little heavily from what I hear). Followed that with two coats of Primocon Primer (almost ran out as well because someone stole one of my cans from under the boat). I finished the drive legs off with Trilux. It looked good on the hard, we'll see how it fairs in the corrosive sea.