3GM30F loss of power and dark smoke from engine compartment

[coxjam]

Help!

Bought a used boat 2 weeks ago, 1989 hunter Vision, which has done a lot of sitting still for past 8 years. no idea how much it has been used but likely, not much. I changed all the fuels, filters, belts, water impeller (didnt change because it was soft, pliable, and intact so left in place). Motor out of harbor today in 26 kt winds to change locale of boat. after 1 hour, motor over heat light came on, we were running her at 3000 rpms or so. Pulled back on power, light went out, ran fine for 2 more hours before it lost power, and dark smoke was iminating from the cabin. Immediately shut the motor down, set sails and sailed for awhile. My friend with me suggested I got some bad diesel so I changed the primary filter again. Motor started up fine after that and ran but I did not run it long, only enough to pull into the new marina and park it in the slip.

what could be wrong?

any help would be appreciated. After changing the diesel filters yesterday, I added 9 gallons of diesel to the balance in the tank. THat diesel ran fine in January when we sea trialled the boat.

thanks,

James

 

[Steve Dion]

Re: 3GM30F loss of power and dark smoke from engine compartm

I would suggest that you have your injectors checked.

You may want to also consider replacing all of the fuel line (rubber).

The heating problem could be your mixing elbow or heat exchanger. What type of fuel filter do you have on the engine and the primary?

 

[Andy1237]

Re: 3GM30F loss of power and dark smoke from engine compartm

Make sure the air cleaner didn't deteriorate and get sucked into the intake.

 

[Ken13559]

Re: 3GM30F loss of power and dark smoke from engine compartm

Mixing elbow fouled up. Very likely black smoke coming out of your air intake. Your air silencer filter is probably gone too. Better get new replacement mixing elbow assembly and air filter.

 

[Bill Roosa]

Re: 3GM30F loss of power and dark smoke from engine compartm

Overheating is not caused by injectors or any other fuel system problem. fuel system problems make themotor not run or run badly they do not make it over heat.
Do you have raw water flow? Yea the impeller was soft but it was also old.
smoke out of an overheating engine (espically on that has sit for a while) is not an emormous concern. Most likly some crud buildup that is burning off with the elevated temps of an overheated engine.
The slow progress of the symptoms and the fact that you can throttle back ant get it to cool down some indicate the problem is in getting rid of the heat. so either the heat exchanger or water flow or lack of anti in the engine. It is also possible (but unlikly) that the fresh water pump belt is slipping. if you can spin the alternator pulley with your thumb then the belt is too loose.
Raw water flow is all about hoses being in ship shape, straners clean, pumps working correctly and that mixing elbo not offering any restriction to flow.
anti in the engine is easy just check it.
the heat exchanger should work if it has water flow on both sides so the only thing left is scale buildup on the raw water side. Pull the end cap and run a bottle brush through it.

 

[coxjam]

Re: 3GM30F loss of power and dark smoke from engine compartm

Thx all.

The raw water strainer was not checked or cleaned.

Antifreeze was topped off and added to low mark on the overflow tank from heat exchanger.

Belts were replaced before home port change on Saturday and verified still under tension when problem occurred. All water hoses "feel good" so not changed.

2hours after problem occurred and new fuel filter was replaced, we arrived at marina and motor starred right up and we were able to dock under power easily.

 

[Scott NIelsen]

Loss of Power and Black smoke.

James,

I suspect your problem is a clogged up exhaust mixing elbow. If you can get it off, take it home and chip the liven daylights out of the inside with a punch and chisel. While you are doing that go ahead and order a new one from your favorite Yanmar source. Mack Boring or torreson. I had a very similar issue a few years ago and did just what I told you to do and the problem is fixed. By the way, I chipped out the old exhaest elbow and reinstalled it to veryfy that was the issue while waiting for the new one to arrive. The new on has arrived and is still in the box. I am still using the old chipped out one. However, as soon as the power starts to wane, that new one is going on lickity split. Bet that is your problem.

Best of success.

Scott "Squatty" Nielsen
S/V PAX (2001 Hunter 320).

 

[kloudie1]

Re: 3GM30F loss of power and dark smoke from engine compartm

I am with the elbow folks.. When ya get it out, make sure the passages for exhaust and water are totally clear.. Check the water inlet fitting carefully.. I found my exhaust passage had coked up so the opening was only about a half inch in diameter.. I chipped it open but it rusted through two years later.. The new one has been in for about 15 years now and is probably about ready for some inspection.. Good luck with it.

 

[coxjam]

Re: 3GM30F loss of power and dark smoke from engine compartm

thank you all for the comments and suggestions. I'll get on it and let you all know what I find. won't be back to the boat for at least a month.

 

[redhead78]

Re: 3GM30F loss of power and dark smoke from engine compartm

I had a similar situation years ago,my partner forgot to open raw water intake an black smoke pouring out of the engine compartment was that nice soft impeller burning up. maybe one of those other problems mentioned cut back water supply. Check your impeller again. good luck Red

 

[RonRelyea]

similar problem - loss of power and black exhaust

I had a similar problem with loss of power and heavy black exhaust last year - although very temporary ... I believe my problem was when I ran through a bunch of seaweed and it hung up on my prop ... after jockeying from froward to reverse a couple of times the prop freed up and problem disappeared ...

maybe your prop is fouled???

 

[sailnteacher77]

Another silent killer is the circulation pump for the antifreeze. 2 hours is long enough for the engine to cool enough to run again. How hot did it get? I had the same thing happen once. Dark smoke from the cabin and dark blue smoke from the exhaust.

 

[coxjam]

Ok, here's the follow up, changed mixing elbow (old one was not that clogged) and heat exchanger was really clogged and motor started right up. Service center recommended thinking about putting a scrubber in the fuel line to help filter the diesel fuel. I ll post again if I have problems starting motor after sailing.

Thanks for all the replies.



QUOTE=sailnteacher77;808600]Another silent killer is the circulation pump for the antifreeze. 2 hours is long enough for the engine to cool enough to run again. How hot did it get? I had the same thing happen once. Dark smoke from the cabin and dark blue smoke from the exhaust.[/QUOTE]