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627Re: Diesel questions continued

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  • wjmfoster
    Nov 16, 2012
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      I'm no guru and I am not a mechanic. I do perform my own maintenance and I am an engineer by day. Here are a few thoughts first, mantras if you will, based on my experience.

      • Start simple/cheap first working up to the most complicated expensive potential problems.
      • Don't borrow trouble. (personally I have a hard time following this, tending to worry about the things that never happen but might)

      First off do you know if the coolant level was topped off this past spring?
      Was the overflow container full of coolant this past spring?

      Barring the answers to the above its hard to say what to do.

      If the answers to the above questions are, you don't know/don't recall or never checked, then following the mantra, start simple I would suggest you top off the coolant, draining the overflow tank for now. Then run the engine up to temperature/load and monitor the situation. This of course may mean waiting until spring and if you do find a problem then you will have to deal with it at that time. I know this may not be ideal as you have all the time in the world now over the winter.

      When you do run the engine, monitor the coolant level closely after running the engine for a few hours at temp. Keeping in mind the coolant expands considerably when hot. Ie: if it's cold when you check first and top it off, as it should be, you will need to wait for it to fully cool off again to actually be able to compare levels. This is also one reason why you may not have had your high temp alarm sound. As the engine warms that fluid level will rise as the coolant expands, more than you think too. This rise may have been sufficient in your case to fully cover the tube stack and permit effective cooling to take place, and if so then I doubt any harm was done on that side of things to the engine.

      Another thing to consider first, before topping off the coolant is, are all the peacock drains on the coolant system fully closed? There are some on the side of the engine for draining it, did you accidently open one while winterizing the engine? Drain it into the bilge? They are on the starboard side of the engine near the lift pump/dip stick, it's all in that same area. Do you have a hot water heater? If so, are the connections here sound or do they leak?

      Next, the drip pan under the engine, is it clean/dry? Or is coolant here, I'm assuming no coolant is here as you sound the sort that would have noticed and commented.

      What about the bilge? Is there any coolant there? I'm thinking if you accidently opened the drain on the engine it might have not been something you saw in the darkness of the engine compartment, the drains have little hoses on them that take the coolant down to the bilge beside the engine foundation. Does the bilge smell of coolant?

      Next, as you suggest, the radiator cap is a relatively cheap/easy place to start. It can be replaced.

      After the above is all verified, then I would suggest seeing about a possible coolant leak in the cooler itself. Ie: pressure test the tube stack, the coolant might just be going out with the seawater via a pin hole leak. This is a relatively easy thing to check.

      Then I would move onto worrying about the head gasket and coolant consumption via the engine. But I personally don't think this is nearly as likely as any of the above. Plus, you note you do not see white smoke/steam in your exhaust. But again, if this were a very tiny leak it might have taken all season with all the hours you use your boat to consume the coolant and at the same time why no visible steam was noted in your exhaust. Pure conjecture and not trying to make you worry but just offering a possible cause/effect, again, after ruling out the easy stuff is my suggestion.

      A mechanic may also be able to offer some advice on intermediate causes/sources of the issue I may be overlooking.

      Your comment re: over propped is a very good one. I too bought my boat last fall and this is my first season with the boat and I agree the 16" x 14" martec is far too much prop. I max out at about 2400 rpm blowing smoke. So I would like to drop down to a 14 x 12, but it sounds like you are doing ok with a 16 x 12? Is this a martec elliptic or the older style martec folding wheel? Just interested in what change I should make as I want to follow your lead on this. Do you find the vibration/noise a problem at the higher rpm's? What speed do you make under power and at what rpm?

      I too have a ton of black smoke when the engine Is loaded above 2200 rpm to 2400 rpm. I operate at 1800 to 2000 rpm now, and still have grim on my stern, but personally I have traced this to my engine having been hard to start this fall. My issue was my engine pull/stop/fuel shut off cable even when pressed in still had the fuel shut off lever on the fuel pump partially closed. So my engine even with wide open throttle would not start. Once I found the problem and manually pulled the fuel stop lever on the fuel pump she would fire right up, but still bump out some black smoke and un-burned fuel onto the water. The source of my dirty transom. I hope to rectify the problem this winter, but I at least know what it is.

      Also a possible source of smoke/unburned fuel stains you might consider being your cause, can be rapid throttling up and down, common during maneuvering. The diesel fuel pump will try to cram more fuel via the injectors into the cylinders to throttle up and the engine will try to burn it and accelerate, but this takes time, and only so much fuel can be burned per stroke. If you throttle up rapidly there will be lag and during this time unburned fuel will be exhausted. This is the same sort of thing as overloading the engine, temporarily.

      What I'm getting at here, is that, regardless of the boat, I tend to see black stains around the exhaust, especially if the boat is white and used a lot. It certainly sounds like you put some hours on your boat/engine and I'm jealous of that, so I would keep it in mind that you have been using the boat and it might as much be the number of hours and combustion by products and unburned fuel at start up that is the source.

      I do hope some of this helps, sorry for the verbal diarrhea.


      --- In J28Sailors@yahoogroups.com, "John" <sailingmaster@...> wrote:
      > I need some advice from the Yanmar gurus amongst the group.
      > I was winterizing the engine last week and found that the anti freeze in the engine was empty. The overflow reservoir was full but there was barely any coolent in the heat exchanger.
      > Last summer the engine ran fine and the temp gauge never got up more than 120 degrees.
      > I am hoping that 1) i have a bad radiator cap and am losing some coolant to evaporation or 2) possibly a bad thermostat causing the coolant to boil out and into the overflow reservoir.
      > I am troubled though that I still get some black residue on the transom from the exhaust....this is the bad news as I know another possible cause could be the head gasket....I hope this is not the case and am seeking some experienced advice before I jump to conclusions..
      > Originally, when I got the boat. It was over-propped and could not even reach 2600 rpm, at that point I would get a lot of black smoke in the exhaust. This summer I changed to a martec 16X12 and the engine runs great and maxes out at 32-3400 (yanmar tach) and there is a slight amount of grey/black smoke in the exhaust. It does however result in a grimey looking transom...is this normal?
      > I never see white smoke at start up (anti freeze?) or blue (oil) although I do burn about .75 -1 quart of oil per season (April 1-Nov 1 and running the diesel 2-3 days in spring and fall and 4-5 days per week in summer - I live aboard July and Aug) I mention all of this in the hopes that this is normal on a 27 yo engine and the hopes that you guys can help me zero in on the mystery of the coolant..
      > Finaly, When I check the oil, I see no sign of bubbles/foam or water
      > Where should I start?
      > Thanks in advance and happy winter
      > JP
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