Finally, after much to-and-fro, up-and-down and backwards-and-forwards, the new exhaust in in!
Back in August the exhaust union gave way in the shipping lanes and, in disgust, I parked the boat for a while. It’s never a good idea to procrastinate because in the end it took quite a while to extract the bits and pieces from the boat and find the parts needed to cobble together a solution.
After a quick visit to the local Yanmar agents I was pleasantly surprised that in 2019 one can still buy all the original parts needed. I was less impressed with the pricing though – R7,900 for a threaded union, mixer elbow and gasket. Thanks to Prof. Google I stumbled on several websites [here and here] showing me how others had replaced their OEM exhaust elbows with home-made solutions.
As luck would have it the local hardware store here in the deep south carries a range of galvanised irrigation pipe fittings, the 40mm range being exactly the same thread match for the existing Yanmar exhaust. The entire new mixer loop is screwed together with the only ‘difficult’ part being to weld the water injection nipple [and that’s only difficult because I weld like a sea-gull and had to find an expert to help me there].
Angle the injection nipple down to guard against back-flooding.
A new water hose was required due to the different angles and spacing.
The online recommendations were to use “Schedule-40 Black Pipe”. I’ve no idea what that is and, although I guess a dedicated dive into the engineering world of pipes and fittings may have shed light on the matter, I’ve decided to stick with my off-the-shelf irrigation pipe solution.
There are obvious concerns using galvanised pipe in a salt-water exhaust system. First and foremost is the corrosion issue. I have no idea how long the new exhaust will last. However, if anything is going to go it’s going to be the injection section and so the plan is to weld up a spare or two and keep them on board in readiness. [At R187 for the entire assembly I could keep a thousand spares on board and still not hit the agent replacement price]
Another online caution was that the galvanising gives off some kind of [toxic?] fumes when first heated to exhaust temperatures. Rather than allowing this to happen on the boat I put the assembly on the bench and let it heat up. This helped to burn off the majority of the zinc and had the added benefit of setting the exhaust paste I used to seal the joins.
After installation I spent a good hour running the motor on the dock, keeping a careful eye on the new contraption. I think I’ll still wrap the loop ahead of the injection point with exhaust tape [when I find some] just to make sure there’s a bit of a barrier between the hot parts and the water hose although I think the spacing is currently fine.
There’s a serious amount of vibration and movement on a YSB12 when running so, as part of my pre-start checks, I definitely be double checking the exhaust loop and all hose connections for fit and tightness in future.
Since installing ‘Blue has been out twice last week already and everything looks good. I’ll be keeping an eye on the installation and plan to report back on longevity or any problems encountered.
But, for now, it’s time to enjoy getting the old girl off the dock once again. 6 weeks confined hasn’t been good for her or for me!