Friday, April 11, 2014

New Exhaust Riser

On our last trip out we had noticed that the engine water temp would climb above 180F anytime we pushed the engine beyond about 2,200 RPM which really puts a drag on our speed.  Having dealt with this problem about two years ago we knew exactly where to look, the wet exhaust riser.  About two years ago we had pulled it off and soaked it in muriatic acid to remove the carbon build up inside the yanmar mixing elbow which resolved the problem up until about now.  Knowing that these are considered wear items and that we managed to get an extra two years of service out of the elbow it was time to fit a replacement.

One of our goals for our boat is to be able to service it ourself anywhere and to be able to find reliable parts easily which meant that the expensive yanmar elbow was off the list and that we were not doing a direct replacement so we would have to build an entirely new exhaust riser.

Our first step was to pull off the existing riser and bring it home to work on building a replacement.

<Picture of Old Here>

Knowing that the exhaust flage was likely never to come off the old riser we opted to order a new one and start from the beginning, this was universal part number 298599.

After that I spent a good deal looking for new parts at the local hardware store and plumbing supply houses.  I tried my best to build the new riser out of black iron fittings to not have to deal with the burn off of the galvanization, however it is rather difficult to find larger fittings locally and I wanted to get this put back together by the end of the week so I ended up with a mix of galvanized and black iron.  The following is the list of parts that I used.

1.  1-1/4" Black Iron Street elbow
2.  1-1/4" x 2" Galvanized Nipple
3.  1-1/4" -> 1-1/2 Galvanized Reducer
4.  1-1/2" x 4" Galvanized Nipple
5. (2)  1-1/2" Galvanized Street Elbow
6.  1-1/2" Black Iron Wye
7.  1-1/2" x 3" Black Iron Nipple
8.  1-1/2" x 3/4" Galvanized Bushing
9.  5/8" x 3/4" Watts Brass Nipple Adapter

I then painted the entire assembly with a High Temp Spray Coating I got from home depot, wrapped it in titanium exhaust wrap and installed it.

The outcome was a significant improvement.  Engine temps were back to normal, the exhaust seemed to flow more freely and there was a significant increase in the quantity of water being ejected from the wet exhaust.