Yanmar mixing elbow again

[Icetug]

The maintenance of Yanmar diesel engine mixing elbows is a continuing topic. This is a situation I ran into that I haven't seen discussed before. The engine raw water pump discharge hose popped off the pump while running at 2700 rpm. No damage to anything, and I was able to put the hose back on and come home at a slower speed. At no time did the engine overheat.

After a search of Yanmar forums and some thought, I decided that the mixing elbow was clogged enough to force the pump pressure to get high enough to pop the hose off of the pump.

I ordered all new parts from Torresen Marine. I did not want to try to mess with getting the exhaust elbow, joint coupling, mixing elbow apart so I just bought all new parts. Total cost (including new water hose) $420.

I inspected the parts after removal and found the small barbed elbow on the mixing elbow had narrowed from 1/2" to 1/8" with mineral deposits. So I feel pretty sure that the high pressure from this clog did cause the hose to pop off.

I will be putting the inspection of this small fitting on a regular schedule from now on. This won't keep the large mixing elbow from slowly clogging but may slow down the process. If you have a Yanmar and run it in salt or brackish water, do yourself a favor and give this item some love before it overheats your engine or pops a hose and fills your bilge.

 

[BroadReach]

Mineral Deposits

The clogging of your small elbow was from salt water.
Salt water has a lot of fun with items such as this when it is heated over 160 degrees F. such as clogging pipe lines.
You may also want to ream out the heat exchanger on the upper left side of the engine. Get a .22 rifle barrel cleaning kit for $8.00 at Wal-Mart
Your may want to check the opening value of your thermostat to insure it is below 160 degrees F.
Living in the New York area chances are your previous owner put a higher heat value thermostat in the engine for winter motoring.
If you ream out the elbow with a screw driver it will work for a good while

Sail On
Broad Reach

 

[Ed Schenck]

Curious. Are the new parts stainless rather than cast? A recent post suggested that a stainless elbow will not coke up like the original cast elbow.

See response #10. Maybe you have to get them custom made: http://forums.hunter.sailboatowners.com/showthread.php?t=130910 .

 

[Alan]

To be honest you probably should have at least attempted to separate the parts. I did this job a few months ago. I replaced the elbow, coupling, and gasket for $200. I reused the exhaust elbow which rarely will need to be replaced. When you assemble the new parts use a good quality anti seize compound and teflon tape to make the dismantle next time a lot easier.

 

[davjonLegend]

Icetug, I am assuming your mixing elbow is U-shaped (like in Alan's picture). And since, you mentioned the "small barbed elbow", I assume you mean the 90-degree fitting for the water injection. Given that, I'll point this out -- the 90-degree fitting that came with the Yanmar mixing elbow was smaller diameter that the one on my boat (a 37.5). So I think Hunter (or someone) had replaced the original 90-degree fitting (your barbed elbow) with a larger diameter one to increase water flow and reduce the effect of mineral deposits. So I had a machine shop easily bore out/thread the hole for the larger fitting. It works well, and the old one had been on there at least 10 years.

 

[Alex Dare]

I've found impeller blades in that "small barbed elbow" that had somehow made it through the heat exchanger.