Yanmar 2GM20F rpms go down and no power

[Brinky63]

My yanmar 2Gm20f starts fine but when I give it more gas it goes to under 2000 rpm then starts heading back to zero. I get no power whatsoever from the engine, no overheating.

The engine does not give the same knocking sound as customary. When below I noticed that air was coming out of the air intake on the side. When I removed the air cover it showed that air pressure is coming out instead of air going in. I'm not an engine expert but believe this has to do with the valves or pistons.

Anyone else ever experienced this and if so what were the next steps?
Appreciate any help or input.

Saludos from Aruba

 

[Davidasailor26]

Any smoke, either in the exhaust or the air from the intake? Also, did this start suddenly our worsen over time? My first suspicion given the air coming out the intake is lost compression and blow-by, but that's just a guess.

 

[kloudie1]

Couple of things to check.. Make sure the valve clearances are set correctly and make sure your exhaust elbow is clear..

 

[Charles Erwin]

I am with Koudie. Could be a hung up (open) intake valve - hence air draws in and air goes right back out. Check them for sure.

I would still start with ruling out a mixing elbow obstruction and examine whether there is some other exhaust path obstruction. If the motor cannot exhaust it cannot intake and you will have some blow back - probably.

Charles

 

[Benny17441]

Ok it sounds like the engine may be running on a single cylinder. You may have a stuck intake valve on the cylinder that is not firing and it just pumping air in and out to the intake manifold. Engine may not have the same knocking sound as the valve tappet may not have any clearance.

 

[NYSail]

What’s coming out of exhaust pipe at rear??

Mixing elbows can cause a heap of trouble if completely blocked.

Start simple.......

Greg

 

[Brinky63]

Thanks all for the input, answers to your responses are:

Smoke – exhaust or intake

o Nothing out of the ordinary from the exhaust

o No smoke from the intake

This started suddenly, earlier that day I ran in the engine in the slip in gear @ 2000 and had good power. Lines were good an tight as in previous runs.

From the responses sounds like I have to look into

o Exhaust elbow or mixing elbow obstruction

o Intake valve

Will get back with the findings, thanks again for the help.

Brinky

 

[MitchM]

sure sounds like your 2 cyl is only running on 1 cyl. that would explain loss of power , too. it’s been my experience that a clogged mix elbowgradually reduces the max rpm sso your engine can no longer hit the power curve. sounds like time for a valve job and while you are at it, exhaust el clean or replace , engine mount check and adjust, and p shaft coupler face out. i envy you being in aruba, there’s a large commercial shipping terminal there that should have some decent diesel mechanics . how many hours on your engine ? what’s its maintenance / service history?

 

[Brinky63]

Mitch,

thanks for the input. yes we have several good diesel mechanics on island. not sure on the hours, i've owned the boat for 7 years and have done yearly general maintenance on it, had a complete check done when I purchased the boat.

 

[Mickstr]

Hate to go crazy unless I need to... have you ruled out a fuel issue? Checked or replaced filters? Checked for a screen in the fuel pickup tube that may be clogged? (This could permit start after sitting awhile, but starve the engine as it runs). Have you checked all fuel line fittings (as in check with a wrench). Have you looked for any air bubbles at all fuel line fittings?
I'd exhaust all of these possibilities before hiring a mechanic.

 

[Tally Ho]

You could open each of the compression levers (1 at a time) to see if either one changes the engine sound. May pinpoint if on of the cylinders isn’t working. If one of them kills the engine, that cylinder is the one working.

But based on some of the other threads on similar subjects, I would pull the exhaust elbow first.

Greg

 

[sailcapt340]

How old is your engine to you, what year is it, and have you ever changed the mixing elbow?
Just went through this, except I had black smoke and fine soot.
Check the Elbow first.

 

[Brinky63]

plan on looking at the filters tomorrow.

 

[Brinky63]

thanks. never changed the elbow. boat and engine are from 2003

 

[Brinky63]

So the verdict is in and it seems with overwhelming proof that the culprit is the mixing elbow. It is completely stuffed, no water was able to run thru it.

The pictures tell the story…….the unit broke in two when we tried turning the elbow in a vice grip.

Any advise on where to order with a good price and fast?

Have a great weekend and thanks again for the help.

 

[Charles Erwin]

Best price superior materials. Call them. https://hdimarine.net/

Charles

 

[jssailem]

The pictures tell the story

Yup... It is a tale of woe and misery often told by boat owners of preowned boats.

 

[Tally Ho]

But hey, hopefully no engine problem! Much easier to replace the mixing elbow and manifold.

Greg

 

[sailcapt340]

Br

 

[sailcapt340]

Brinky63,
I purchased all my parts locally in Rhode Island (smmarine.com) and needed the same parts as your pictures show. $401.00.
Try toadmarine.com they have the parts, not in stainless as HDImarine. When I contacted HDI they were our of stock for my model engine (3GM30F), so I opted for the original replacement parts.
At least you could separate your elbow. I'm still trying to do that with mine so I can get inside pictures.
I'm sure it will solve your situation.