Does your engine have bad breath?

[robertsapp]

I'm trying to define "normal" so that I don't drive myself crazy trying to fix something that isn't broken. After fixing some hidden diesel leaks and other things that the PO let go, and then following Peggy's advice about scrubbing everything and then using a garden sprayer full of PureAyr, we have our boat smelling nice and April fresh. Among other things, we had a pretty bad exhaust odor in the aft cabin that would bother us while sleeping, and to try and fix that, I replaced everything in the exhaust system except the manifold/heat exchanger and muffler. So here's the thing - when the engine is running, there's no odor in the rear cabin at all. Absolutely no exhaust or other acrid odor. But after turning off the engine, a definite acrid odor will fill the aft cabin. It's as if the engine exhales something for a while after it's shut down that finds its way into the aft cabin. I've taken to dealing with it by going below, turning on the bulkhead fan, and pumping a few squirts of PureAyr or Febreeze into the air after shutting down the engine. The fan cirulates it around and 10 minutes later things smell fine again back there. So my question is, is this normal? Or is there something wrong here? I do have a carbon monoxide detector back there, and it has never alarmed. Does my engine have bad breath?

 

[kloudie1]

Might be the smell of the hot motor oil exhaling through the breather.. or the hot transmission oil .. Ya might want to check to be sure someone didn't put gear oil in the transmission.. Try changing oil in engine and transmission with the correct stuff and see if the smell gets better?? I dunno..

 

[robertsapp]

Engine and transmission both filled last October with Shell Rotella 15w-40. I'm thinking though you're on the right track - maybe some exhaust drifting out the intake and breather once the engine is shut down and no longer pulling fresh air into the engine box. Makes me wonder if I should install an exhaust fan similar to what gas powered boats use to exhaust gasoline fumes prior to starting. Maybe run it for 10 or 15 minutes after shutdown. Anyway, like I asked before, is this normal?

 

[kloudie1]

Not normal for my engine, Robert.. sounds like ya have the correct oil.. The blower sounds like a solution but I am curious about the real cause.. When you pull the stop button or turn off the fuel solenoid, the engine should consume all its fuel before it stops and should not exhale exhaust.. In coasting to a stop, it will continue to pump clean air from intake through exhaust..

 

[Jay Meyer]

Got your fix !!

Robert. -

I put a inline blower on my 2001 H380 for the same reason. I flip it on for a few mins on long runs (I really never have any over 30 mins.) and let it run for 10 mins after I shut the horse down.

Take a look I my installation as I know it will work for you. At the home page go over to SEARCH and choose Owner Mods, then search Blower, under Jay Meyer you will find it. Feel free to email me at sailing84@aol should you have any questions. Took me about 4 hours, and $65 worth of parts + one cold beer.

 

[kloudie1]

Nice work, Jay.. I am getting ready to install a blower as well but to get rid of the heat and not smell..

 

[Dan Johnson]

Hey Claude...

I've had a 4" bilge blower sitting in a v-berth cabinet for two seasons trying to figure out where to install it and where to route the hoses in and out. Let us know and take pics of what you decide.

 

[Bill Roosa]

I'd invest in a CO warning "badge" till you can confirm that the smell is not something that is going to kill sombody. Smells like you describe would have to be exhaust leaks (very bad) or oil burning off after the engine stops and you experience the normal temp spike upon shutdown.
One thing to try to determine if it is the latter is to idle the engine for about 5 minutes before shutting it down. This gives the whole engine time to cool off and you do not get nearly the temp spike upon shutdown.
Course, you say everything has been scrubbed down so that would lead me to believe exhaust leak. The CO "badges" are pretty cheap insurance.

 

[robertsapp]

Jay, your mod looks exactly like what I was thinking. Good to hear it works for you, I might have to add that to my summer projects list. Regarding an exhaust leak, we've done runs on the intracoastal where we've motored for three or four hours, and we don't get any odor in the aft cabin. It's only when we shut the engine down that the smell appears. I would think an active exhaust leak would be most noticeable when the engine is running, rather than after it is shut down...? I follow the logic about how the engine coasting down should purge the system, but my latest theory goes something like this: after shutdown, the final exhaust fumes collect in the riser downstream of the mixing elbow. As exhaust pressure drops to zero, water in the muffler flows back toward the engine and up the riser to the level of the surrounding seawater, in the process pushing a couple of liters of exhaust gasses back through the mixing elbow, exhaust manifold, and then through any cylinders that may have an open exhaust and intake valve (how many degrees of crank rotation are both valves open? Is this likely?). Then out the intake and breather, and into the surrounding air. Hey, it could happen, right?

 

[kloudie1]

Dan. mine is under the table in the main cabin !! still in the box.. Soon maybe..??

Robert, ya may be on to something there.. I hadn't thought of that.. some of the engine's valves are pretty much guaranteed to be open and if the run from the muffler is a bit long and uphill, the residual water in the uphill section could very well run back to the muffler and push some really smelly vapor through the engine.. it may also be coming out of the syphon break on the line between the manifold and the exhaust ell?? Ya might pull that little valve and make sure it is clean and free to work..

 

[robertsapp]

Long and uphill would be a pretty accurate description of the exhaust hose on my boat.

 

[marginal]

Question... Do you have what they call a Vetus neck on your exhaust line ?

 

[robertsapp]

I don't think so. The name Vetus makes me think of a vented loop, and we do have a vented loop on the seawater line from the heat exchanger to the mixing elbow, but it's a stainless loop with a plastic vent valve, not a Vetus model. Beyond that, from the mixing elbow it's 2" wet hose down to the in-line muffler, and then more 2" hose from there back to the stern, with about an 18 to 24 inch hump in the hose before it goes overboard under the stern. Total hose run is 12.5 feet, plus the muffler.

 

[marginal]

Vetus Waterlock stops water from coming back to the engine... Maby it can help if the problem is related to water coming back to the engine.

http://www.frenchmarine.com/product/Vetus-Waterlock-LP40R-LP45R-LP50R-571-97

 

[Jay Meyer]

Robert - I mostly put blower in for evac of heat from eng compartment.

Jay, your mod looks exactly like what I was thinking. Good to hear it works for you, I might have to add that to my summer projects list. Regarding an exhaust leak, we've done runs on the intracoastal where we've motored for three or four hours, and we don't get any odor in the aft cabin. It's only when we shut the engine down that the smell appears. I would think an active exhaust leak would be most noticeable when the engine is running, rather than after it is shut down...? I follow the logic about how the engine coasting down should purge the system, but my latest theory goes something like this: after shutdown, the final exhaust fumes collect in the riser downstream of the mixing elbow. As exhaust pressure drops to zero, water in the muffler flows back toward the engine and up the riser to the level of the surrounding seawater, in the process pushing a couple of liters of exhaust gasses back through the mixing elbow, exhaust manifold, and then through any cylinders that may have an open exhaust and intake valve (how many degrees of crank rotation are both valves open? Is this likely?). Then out the intake and breather, and into the surrounding air. Hey, it could happen, right?

 

[Jay Meyer]

Robert - I did add a length of 4" pvc to the hose and set it up vert. terminating about 4" from top of eng. compartment to get the "hot air".

 

[mr c]

I was always told to rev up the engine just prior to shutting down to get all exhaust gases out. This will allow the exhaust to expel and will not prematurely clog the mixing elbow.

 

[seadaddler]

Try

Try checking the mixing elbo maybe the mixing elbo is slightly clogged and some of the exhaust gases some how is leaking in the rear berth.
If you cleaned the mixing elbo will help the engine and boat to perform better any way for sure.
Nick

 

[lr172]

(how many degrees of crank rotation are both valves open? Is this likely?).

About 45 degrees or less out of 720 degrees. Further, this overlap happens at TDC and engines rarely stop in a configuation with any cylinders at TDC, especially a two or hree cylinder.

 

[Bill Roosa]

Hey Mr. C
You need to ask the friend that told you to rev up to get rid of exhaust gas how reving the engine can possibly get the exhaust out when running the produces exhaust.
Perhaps he meant gets the water out of the muffler.
Not sure I'd want to do that either as once the muffler (reving will get water out of a muffler) is nice and dry and you come back the the boat the next weekend you start the motor and the exhaust is dry, gets hot till the water starts to flow and refills the muffler then everything is OK. If you just leave it with water in it you don't have to refill upon restart. I would do this as a very last thing with the engine before pulling the boat for the winter to get as much water out of the muffler though.