Good day to all,
For those of you who are fairly new to their boats and are not completely sure that the previous owner ran their generators at the proper load or whether that is effective enough, I would urge you to take the time to remove your Onan exhaust elbow and inspect for carbon build up.
We purchased our SM a little over a year ago. The previous owners were adamant with me to always run the Onan with a high load when they generously spent four weeks with me during the purchase transfer/training period, and I adhered to this regimen.
A few weeks ago, the generator started acting up. At first, it would not handle a full load, then, it would not run at all.
When I inspected the exhaust elbow, I found it was about 75% clogged with carbon, and the exit port on the exhaust manifold was nearly 100% clogged. I was hopeful that cleaning both the manifold and elbow would solve our problem, but it was too late. The back pressure from the exhaust must have broken some of the piston rings as only one of the 3 cylinders had compression that met specs.
This was an unnecessary early death for unit that only had 3300 hours on it. I read on the forum about another owner who found similar deposits at only 2000 hours, allthough I believe he was able to save his.
We could rebuild the engine, but we have decided to replace the whole unit instead and remove major components for spares. We are going to do the work in Martinique as soon as the new unit arrives.
Checking the elbow was on my ‘todo’ list, but too far down to get to in time.
As the previous owners were insistent that the unit be run at high load, I’m not sure if this is a case of them not always practicing what they preached, or if the design is just prone to clogging. For this reason I urge you all who may be unsure of current conditions to do an inspection. I am planning on checking the new one after every 500 hours or so until I can acquire enough empirical data.
All the best,
SM #466 - s/v Rita Kathryn
Rodney Bay Marina