Engine trouble - los of power

[Dixon Hemphill]

Hopefully someone can tell me why my Yanmar 2GM20F diesel engine acted up today. We motored over 2 hours into Chesapeake Bay at 2800 rpm normal speed with the engine running smoothly as usual al summer. After a great 2 hour sail we headed back to the marine.

1. The throtle was pushed to max but top speed was 2000 rpm
2. Some white smoke showed at the exhaust
3. After a 1/2 hour the rpm dropped to 15000
4. After an hour of motoring max speed was 1000 --- whth engine running smoothly and no white smoke.

No engine lights came on, oil level was OK, no fuel was added today. Any ideas, sailors?

[Oswego John]

Rule of thumb:

Blue or dark exhaust smoke - oil.

White smoke - steam - water. Check your oil dipstick. Look for water bubbles on it. Oil floating on water in oil pan could give a false reading of oil the level. Possible cause,- blown head gasket. Take a compression check.

Dixon, these are random, first thoughts I had. It is very possible that something else could be causing the trouble.

Also check your fuel filter from being clogged.

Good luck.
O J

[Jim Evans]

I wonder if someone inadvertently partially pulled out your fuel shutoff knob during your sail? Or perhaps your air intake is partially blocked?

I'll be interested to hear what you find - I'm quite confident the solution is relatively simple (I hope!).

[Klem]

An engine that won't rev up usually either has too much load on it or not enough fuel.

How does the engine perform in neutral? Will it rev normally?

Too much load is caused by a fouled prop, seized cutlass bearing, transmission problems, etc but generally won't gradually get worse, it tends to just happen. In your case, it sounds unlikely. A dead giveaway that it is too much load is a lot of black smoke out of the exhaust which it sounds like you don't have. A quick dive overboard to look at the prop and then some manual turning of the shaft with the transmission in neutral will rule out most of this stuff.

Too little fuel has many possible causes, some of which are easy to diagnose, others are more difficult. The most obvious one is the shutdown on the engine, if it is partially engaged, the engine will have reduced power. Another likely culprit along the same lines is a throttle cable that is coming unhooked at one end, the easy way to check this is to disconnect it from the engine and hand throttle it. Did you just fuel up? You do show some signs of badly plugged fuel filters. As they plug up more and more, less and less fuel can pass through and the engine revs less and less with nothing seeming to be wrong otherwise. If nothing else, it may be worth changing them and then cutting open the old ones to make sure there isn't junk in there. Air leaks in the fuel lines can cause some problems like this but usually the engine runs pretty rough. There are also some more complicated problems inside the IP but they are unlikely and you should rule out all of the easy stuff first.

You did mention one strange thing which is white smoke. White smoke is either poorly combusted fuel or water. Water would get into the combustion chamber through a leaking headgasket but I have never seen it get bad enough for the engine to loose significant power. The other thing that it often means is slipped timing. I have not heard of these engines having this reputation and it would be very strange for it to gradually get worse (it tends to slip and stay there).

Good luck.

[grajmahal]

I got to know that little engine pretty well during the years that I lived with one in my Beneteau. Others have mentioned your fuel filters - diesels like their fuel clean, especially the mechanically injected ones, so there should be several filters in this system. Hopefully you have a large, clear-bowled Racor or equivalent that will allow you to see if there is a lot of stuff in the fuel. Dirt and water will get you every time, and sometimes you don't know it is in there until you have some heavy weather that stirs up sludge in the tank. Diesel in the summer heat can also develop a fungus that grows right in the tank and makes a mess of everything.

If you find stuff in there, check the small factory fuel strainer just adjacent to the lift pump on the upper starboard side of the engine. It is in a small cylinder about the size of a can of tomato paste. You just remove it, blow it out, and put it back (it is reusable)

I agree that white smoke in the exhaust sounds like water, but if you are saltwater cooled, there is always going to be some steam mixed in with your exhaust. The injection elbow on the exhaust causes problems on these things, but usually that results in some sooty discharge instead. Still, it doesn't cost a thing to take it off and have a look inside. They fill up with salt residue and become constricted, and all you have to do is scrape the crud out of there.

A blown head gasket can also have this effect, but you want to rule out everything else before you go tearing off the head. (It is actually surprisingly easy to replace - I did it in a marina in the Bahamas with tools on board and a torque wrench) . The edges of the gasket on that motor are aluminum, and they are very thin - the presence of salt water in the water jacket eventually eats them away and the gasket fails. If this is the case, you will find that the engine becomes harder and harder to start. If it gets to the point that you can only get it to pop over by holding the decompression lever for one (but not the other) cylinder, then you probably have a blown gasket.

Best of luck and PM me if I can be of any help! My memory of these things is starting to fade now, but as I said, I was married to one for a couple of years.

John B

[Dixon Hemphill]

Many thanks for the helpful suggestions you experts have sent me. I'm sure one or two of the many solutions you have suggested are the answer.

I will go to the boat this Wed and one by one will investigate each suggested solution. Thursday I will tell you what I find was the problem --- I hope!

[Dixon Hemphill]

It turned out to be a dirty fuel filter that caused my engine to slow down to 1000 rpm. I don't recall how long it had been since this filter was replaced but it sure was time to do it today. Engine now works like a charm!

Thanks to those of you who made the various suggestions as to what caused the problem.

[Klem]

That is great news. Did you happen to cut open the filter and see what was in it? Hopefully it was just years of accumulated crud but you want to make sure that you also don't have a bad fuel problem.

[grajmahal]

Klem, that would be my worry as well. Usually if the problem surfaces after a daysail, it was crud in the bottom of the tank that got stirred up by your angle of heel. Where there's crud, there's usually more crud. A tank inspection is in order.

John

Typhoon weekender #108

[Dixon Hemphill]

Valid suggestions, Klem and John. I may have crud in my fuel tank so the next chance I get I will try to clean out the tank.