Yanmar Diesel Question

[Dick Dixon]

For all the Yanmar diesel folks.....I have a 1993 30 HP three-cylinder raw water cooled diesel. The engine has approximately 1800 hours. Over the past few months her power has diminished while under load from 2800 down to no more 2400 RPM. Along with a obvious loss of power, she produced some white/grey smoke at normal RPM but when a real load was required black smoke would exit and the engine would bog down. I pulled the injectors and had them tested....they were found to be in great shape...a cleaning was performed however. When I removed No. 1 cyclinder's injector, I found the O-ring to be in bad shape with apparent "blow by" occurring. I replaced the O-ring. There is no smoking now. I also changed both fuel filters (which is done annually anyway)and bled the system. All three cylinders are firing; the engine runs exceptionally well when no load is present, easily reaching 2800-2900 RPM's with no problem. But once load is engaged she will not climb beyond 2400 RPM's. Also, no coolent is escaping into the engine. Additionally, the raw water impeller has been changed recently. The propeller is clean and there appears to be no mechanical prolem in the shafting. The breather is clean and clear.

Today I plan to pull the mixing elbow and perform cleaning maintenance. Since I've only owned the boat for 4-1/2 years, I'm unsure of its age.

If it isn't the mixing elbow, does anyone have an idea as to what may be happening?

Thanks,

Dick

 

[Ed Schenck]

Bet is on the elbow.

Pretty certain that you will find the elbow all coked up. If not then most certainly something else in the exhaust system. We will wait for you to report back.

 

[kloudie1]

Yanmar Diesel

I am in agreement with Ed.. My exhaust elbow on a 3GMF had coked enough that the opening was less than a half inch in diameter. It also caused some overheating if run at high power settings for some time.

 

[Dick Dixon]

Seems To Be the Problem

Today I pulled the mixing elbow and found what I suspected. The first thing I found was the small rubber hose from the heat exchanger was chocked with deposits. The mixing elbow itself was clogged down to less that 1/4" or less on the downstream side of the exhaust portion. Tapping it with a hammer along with using a screw driver as a pick caused large chunks of carbon and corrosion to fall out of the chamber. Flushing it with water really caused additional debris to come out. While attempting to remove the screwed fitting that attaches the mixing elbow to the engine exhaust fitting, the elbow cracked and eventually broke open. We were then able to see other corrosion deep inside. None the less, it is time to replace the mixing elbow.

Thanks for the advice.

Dick

 

[Ed A]

boy these guys are good

they always get it right!

 

[Paul Akers]

When You Get the Elbow Off...

...you would be better off replacing the elbow because it won't be long before you will need to do it again. Take my word - invest in a new one to replace the old one.