Steamed?

[Kevin L.]

As I was motoring into the fuel dock the other day, a local marine mechanic called out to me something to the effect that there was steam coming out of my exhaust port. After some querry, he advised me that there should not be any steam exiting the exhaust system, and that steam was evidence of insufficient water flowing through the exhaust sytem. He then went on to suggest flushing the system with Muriatic acid to loosen rust, scale, etc., and of course volunteered to trouble-shoot the entire raw water cooling system, water pump, thermostat,etc.

Now, understand that my MD7A runs consistently in the bottom fourth of the temperature guage. I can even see the thermostat cycling in minor fluctuations of the guage. But I have noted that after long periods of motoring, say a couple of days pretty much non-stop, the exhaust system (aqau-lift muffler, etc.) show signs of some pretty high temperatures. Like paint flaking off the muffler and exhaust hoses showing signs of minor seepage.

Let's not talk about impellers, because I change mine every year. Could there be a blade lodged in there somewhere due to a previous Owner's sins, perhaps. But I am curious whether other Owners see steam coming from their exhaust, and what could be seen as normal in terms of system temperatures. I should probably mention that I ditched the factory's stainless steel aqualift in favor of a fiberglass unit a couple of years ago, but the geometry of the revised system is not appreciably different from the factory setup.

Gentlemen, avail me of your wisdom.

Kevin LeMans
CD30 Raconteur
San Francisco



lemans@gte.net

[Patrick Turner]

Kevin,

I have seen some steam after motoring along for a few hours at at higher rmp (2800). I mentioned it to a mechanic friend of mine and he said essentially what that fellow told you - that it was do to restricted flow. Could be the raw water filter if you have one, could be the sea stainer on the hull has lots of paint on it.. Since my engine is virtually new (last year) I suspect that my sea strainer is the culprit and will check it out next haul out.. I'm not a mechanic, but I don't get the impression that it's a serious condition......on that should be figured out tho

Pat



patrick.t@attbi.com

[John R.]

There are certainly several things that can cause white smoke and I wonder whether what is occuring is either smoke or actual steam. Since you stated engine temp is reading low and assuming you are getting normal water flow from the exhaust outlet at the transom then I would say your cooling system is fine and no need to be concerned about broken impeller blades etc. Also you state that the muffler paint is peeling so you best double check that temp gauge for accuracy and make certain you have good water flow at the transom.

If the water flow is good then it appears you are actually not seeing steam but rather white exhaust smoke. White smoke is caused by some of the following:

1) Blown head gasket (should cause engine temp to be higher than normal), or some other reason water has gotten into the cylinders.

3) You may be getting blow by of one or all valves as a result of some type of vale problem like poor clearances or guide problems.

5) You may have some piston blow by.

4) How clean is the fuel? Dirty fuel can cause white smoke and so can an air leak in the fuel line.

5) Make sure your decompression levers are in the full unengaged position.

Check the cheap obvious stuff first and if everything seems normal then get a qualified mechanic to check the compression and valves. Also be sure to replace that leaking exhaust hose. You don't want any CO getting into the boat cabin area.

As I was motoring into the fuel dock the other day, a local marine mechanic called out to me something to the effect that there was steam coming out of my exhaust port. After some querry, he advised me that there should not be any steam exiting the exhaust system, and that steam was evidence of insufficient water flowing through the exhaust sytem. He then went on to suggest flushing the system with Muriatic acid to loosen rust, scale, etc., and of course volunteered to trouble-shoot the entire raw water cooling system, water pump, thermostat,etc.

Now, understand that my MD7A runs consistently in the bottom fourth of the temperature guage. I can even see the thermostat cycling in minor fluctuations of the guage. But I have noted that after long periods of motoring, say a couple of days pretty much non-stop, the exhaust system (aqau-lift muffler, etc.) show signs of some pretty high temperatures. Like paint flaking off the muffler and exhaust hoses showing signs of minor seepage.

Let's not talk about impellers, because I change mine every year. Could there be a blade lodged in there somewhere due to a previous Owner's sins, perhaps. But I am curious whether other Owners see steam coming from their exhaust, and what could be seen as normal in terms of system temperatures. I should probably mention that I ditched the factory's stainless steel aqualift in favor of a fiberglass unit a couple of years ago, but the geometry of the revised system is not appreciably different from the factory setup.

Gentlemen, avail me of your wisdom.

Kevin LeMans
CD30 Raconteur
San Francisco

[Ben Thomas]

Kevin, On my 82 cd30 the sea water intake seacock is only 1/2" inside diameter. ( running the volvoMD7A) this limits the gallons per minute that can be drawn through that orifice. If there is an obstruction or problem within the cooling system this can only add to the hot mix. I just repowered with the beta-marine 20hp. I had to change out that seacock to a 1" to accomodate the rise of heat generated at sustained higher rpms.
It only takes a minute or less to destroy those impellors with a secock closed, the water is its lubricant. Seaweed can be drawn up very easily, a plastic baggy anything can plug the strainer to cut flow if even momentarily.
I made the mistake of not opening seacock when motoring to fuel dock recently, the engine ran less than two minutes, thereafter it was blowing steam, engine heat alarm sounded at 204*. I shut engine down (no damage) except Impellor blades were gone, lodged in heat exchanger tube stack. Don't hesitate to check the obvious. Best regards, Ben



bt@benthomaslandscapers.com

[Ken Coit]

If the engine really does run cool for days on end at cruising RPM, then I'd bet on the geometry of the head and block changing enough after hours of running to cause a leak from the water jacket to the exhaust ports/manifold. Has the head been torqued down lately? Is the engine somewhat reluctant to turn over after standing for a long time? Is your oil turning to the color of coffee-with-cream and getting frothy? If the engine is leaking water into the cylinders, you are risking a hydrostatic lock that will damage all sorts of parts, especially the crankshaft and bearings, so you ought to be certain that is not happening.

Keep on sailing,

Ken Coit, ND7N
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC

As I was motoring into the fuel dock the other day, a local marine mechanic called out to me something to the effect that there was steam coming out of my exhaust port. After some querry, he advised me that there should not be any steam exiting the exhaust system, and that steam was evidence of insufficient water flowing through the exhaust sytem. He then went on to suggest flushing the system with Muriatic acid to loosen rust, scale, etc., and of course volunteered to trouble-shoot the entire raw water cooling system, water pump, thermostat,etc.

Now, understand that my MD7A runs consistently in the bottom fourth of the temperature guage. I can even see the thermostat cycling in minor fluctuations of the guage. But I have noted that after long periods of motoring, say a couple of days pretty much non-stop, the exhaust system (aqau-lift muffler, etc.) show signs of some pretty high temperatures. Like paint flaking off the muffler and exhaust hoses showing signs of minor seepage.

Let's not talk about impellers, because I change mine every year. Could there be a blade lodged in there somewhere due to a previous Owner's sins, perhaps. But I am curious whether other Owners see steam coming from their exhaust, and what could be seen as normal in terms of system temperatures. I should probably mention that I ditched the factory's stainless steel aqualift in favor of a fiberglass unit a couple of years ago, but the geometry of the revised system is not appreciably different from the factory setup.

Gentlemen, avail me of your wisdom.

Kevin LeMans
CD30 Raconteur
San Francisco

parfaitNOSPAM@nc.rr.com