Stuck in the Mud - Yanmar 3HM35F

[hkstone]

Question: why would air get into the fuel when a load is incurred? Getting out on my boat (88' Legend 37 - Yanmar 3HM35F) has recently become more difficult since mud has replaced most water in my marina. Once the tide is high enough, it's possible to get out, though the motors labors. The motor pushes through the mud and I can tell it's being over-worked by the exhaust sounding somewhat muffled and a little black smoke. If this continues for say four minutes, the engine starts to degrade I have to increase the throttle and soon it will conk out (I'm not sure if the engine is over heating, since no alarm sounds and no overflow). To get the engine restarted, I have to bleed the system (usually at the fuel injection pump). I have replaced the hoses from the fuel tank,primary/secondary filters, crush washers and there is about 1/4 tank of fuel and by all indications everything is dry (no diesel drips). Any suggestions would be appreciated.

 

[Warren M]

Mud...

I'm not sure that air in your fuel system if the problem. Sounds to me like you are pushing your boat thru mud as opposed to thru muddy water. If the former is the case, I think you are risking serious damage to your engine and associated systems and running gear, including your prop, shaft, and strut. If you are going thru mud, you are adding an unknowable load on your engine to overcome the resistance. You are also probably sucking a lot of mud and gunk into your raw water cooling system that could cause serious damage to your water pump and heat exchanger, as a minimum. I wish I had a positive suggestion, but all it would be is to council caution on your part -- and to look for a deeper water marina.

 

[Daryl2400]

Here's what I think

Tie the boat to a dock and try to recreate the rpm's and time. I doubt the engine stalling has anything to do with mud. Air in the fuel line will stop any diesel.I'd shut off the fuel valve at the tank and disconnect the fuel line at the final filter. Then put air pressure in the fuel line and look for leaks in the system using a snoop type fluid (soapy water in a squirt bottle) Seems like there must be an air leak somewhere in the system

 

[hkstone]

Good Suggestions

Thanks for the responses to this odd problem. One thing I saw in another posting on a Legend 37 was an issue with the fuel tank that may have relevance. The tank (35 gallons) is fairly flat and the pickup tube is outboard, so that it's possible to suck air if the tank is not full and heeled. This might be part of the issue, since before returning, I had been heeled over fairly far and had motored briefly until the sails were set. The solution to the problem was to move the pickup tube to the center of the tank - makes sense.