Fuel Sheen in exhaust water?

What do you guys make of this?

Engines are Yr 2000 Volvo Tamd74P. Two weeks ago weather turns cold. Low 30's for 3 days and actually some snow. Water temp is in mid-50's.

While running the engines at idle at the dock just after the cold snap, I notice a distinct sheen of diesel coming out of exhaust on both port and starboard motors (port a bit worse). Both were also running a bit smokey. Nothing crazy but more than normal. Did not seem to get any better as engines continued to idle, perhaps 15min before I shut down. I've never seen the fuel sheen before although, for a variety of reasons, this is the latest I've ever had the boat in. So, I chalked it up to cold weather.

Fast forward about 5 days. Air temp is now warmer, high 50's to low 60's. Water temp the same. I fire up engines again and same sheen. Now I run the boat on plane to my winter storage facility (about 50min underway). But engines run normally, come up to usual operating temp and no unusual smoke on throttle up or at cruise.

But, when I arrive at dock of winter storage facility (approx 10min idle out of channel, 20min on plane, another 20min at idle before docking), sheen is still there when we get into a slip. Perhaps a bit less but still noticeable.

I am still chalking it up to cold since water temp is lowish and it's both engines. But it seems odd that after motors are heated up it would still be an issue.

Curious your thoughts?

How many hours on the engines?
How many hours this season?

Ted

O C Diver said:

How many hours on the engines?
How many hours this season?

Ted

Click to expand...

3000hrs since new. This season pretty typical for me of about 50-60. But boat has been run very little since beginning of September.

Did you do an oil change before winter layup? Maybe oil analysis would be a good idea.

Ted

Don't pay too much attention to the air temp. The water temp is probably a more significant factor for initial start engine temp, and it was the same both times yielding similar results. 20 minutes idling at the end of the trip may have just put your engine back into the same condition as startup. Would have been good to have stopped the boat after the hard run and checked for sheen. You can do it next season, I guess.

An oil test would be a good idea assuming you have not yet changed the last years oil.. When you get the results post it here in PDF. THere are people here that can offer a decent opinion.

When the weather turns cold lots of diesels will smoke. Especially when run at idle. The combustion chamber is cold so the fuel does not burn completely.
Running at idle will NOT warm the engine appreciably so the engine will continue to smoke.
When you returned to idle after the run the engine cooled off once again into the smoking range.

If it didn't smoke or only very lightly in the warm weather that is likely what is going on. Many engines smoke at startup time , ambient cold or warm. Some only noticeably when really cold.

Don't idle your engine for any length of time. Get ready to go using only those lines needed to secure the boat, then start and go. Allow a few seconds or a minute for the engine to be stable as some will bobble a bit when first started in the cold.

Get a light load on the engine and they will warm up much faster. As the engine warms a bit more push the throttle up a bit more and the smoke should be disappearing.

As soon as I am clear of the marina I push up to about 1,000 revs and continue like that for a while. THen start pushing the engine up a couple hundred at a time.

100% normal. The water temp in the bay is low enough so your engines cool quickly when the load is removed. As soon as those engines come just a few degrees off of normal operating temp they will not burn all of the fuel and you will get residual in the exhaust / water.

Cigatoo said:

100% normal. The water temp in the bay is low enough so your engines cool quickly when the load is removed. As soon as those engines come just a few degrees off of normal operating temp they will not burn all of the fuel and you will get residual in the exhaust / water.

Click to expand...

I agree. Normal. When my boat was in San Francisco area, no smoke from the 3208. Now in the PNW, they smoke until up to temp.

Yep, normal. Charge air cooler brings intake air to whatever sea water temp is, not dependent on outside air temp. Most all TA diesels do this in the winter.

With cold charge air, not all fuel gets burned. Some comes out as a vapor making blu-ish smoke and some of that vapor condenses in the exhaust water, making a sheen.

The time to be concerned is when discrete droplets of oil start to spit out into the sheen. That could be an indication of lube oil.

Greetings,
Mr. P. When was the last time the injectors were serviced? One or two may be "slobbering" a bit.

Thanks everyone. Really appreciate the replies. I agree cold is the likely culprit, mainly because it's both engines, and appeared in both engines at the same time after the weather/water temps turned cold. Injectors were serviced about 6 years/300hrs ago. Perhaps time to do them again. But now that boat is hauled, I'll likely just wait until spring and see what happens. I've never had an issue in warmer temps so if it goes away next seasons I'll know for sure. If not, will need to pursue further.

Totally normal!

Not time for injector service at only 300 hours, but check your manual for proper intervals.

I replaced my injectors at about 5K hours and 37 years on my stb 3208. Pro’s generally said it probably wasn’t necessary, but I wanted to see if there was an appreciable decrease in smoke. Outcome....a tiny bit, not needed. Didn’t do the other engine, just keeping the extra set for spares.

I run slow a lot, so slightly gummed rings is most likely. Could also be slightly oval valve guides, but mine were not even close to ugly when I had the valves out. Nice to get a set of eyes on things, but I know that I for one often go looking for problems prematurely when anything is not perfect. With a 40 year old boat, that fruit is ripe for picking.