steam from diesel exhaust

[Burnham Bob]

before we start examining everything in sight does anyope have any suggestions? there are clouds of steam in from my friend's boat's exhaust. It's definitely steam - no trace of diesel exhaust and the steam is pure white. The engine is not overheating - at least not enough to set off the alarm. the oil is not emulsified so its not the head gasket and with the steam we are getting some water out of the exhaust

Our inexpert opinion is that maybe the raw water flow is not as much as it should be making the engine run hot or, as the alarm isn't going off, not being enough to cool the exhasut gases as much as it used to.

Possible causes therefore are partially blocked heat exchanger, partially blocked raw water inlet or impellor having lost a fin.

Or do the experts have any other suggestions?

 

[NormanS]

It could be any of these things. Another possibility is a partially blocked exhaust elbow (where the cooling water mixes with the exhaust gases).

Another. Apparently, on our boat, shortly before our ownership, lots of hair was pulled out trying to solve similar symptoms. It turned out to be internal delamination of a rubber tube between the water strainer, and the gearbox cooling. Being on the suction to the pump, the delamination had the effect of blocking the hose, but on examination, there was nothing to see. Good luck.

 

[SparkySailor]

What type of engine/transmission?
My Penta MD2030 with Saildrive did the steam thing and only +5hour hard runs set off the alarm... Made a seperate thruhull for coolingwater Teed together with the hose from the saildrive, did the trick LOADS more water with the exhaust gas.
Cant say the thruhull idea was my own, was our local marine mechanic who said the saildrive usually fouls up ad reduces flow.

Hope that will sort your friend

 

[ianat182]

Suggest that first you check the raw water filter for weed and detrius.Next, if filter is clear detach the raw water hosewhic is fitted to the seacock and raise this hose above the water level. I use a inflatable pump to blow through,usually two or three pumps clear anybasny mmuuels or weedy obstruction from the inlet hose. Lower the height of the hose and checkthe volume of the incoming flow, if still poor it may need a wire brush about foot or so long to thoroughly scrub any remaining blockage. If you inlet is covered by grid you may still have a problem forcing the blockage through .Finally purchase the correct gasket for your raw water pump make,then remove its faceplate to inspect for impeller failure and or renewal, and inpteect the face plate for any excessive wear . Some faceplates are reversible or you could get it refaced .
I have very recently had a similar raw water failure and tackled it as above,fortunately the first step was sufficient to get the engine restarted and properly cooled but the heat exchanger also was topped up with fresh water before restarting and later addng the correct antifreeze for the winter.I hope this is of some assistance.

ianat182

 

[ianat182]

Suggest that first you check the raw water filter for weed and detriuts.Next, if filter is clear detach the raw water hosewhic is fitted to the seacock and raise this hose above the water level. I use a inflatable pump to blow through,usually two or three pumps clear any mussels or weedy obstruction from the inlet hose. Lower the height of the hose and checkthe volume of the incoming flow, if still poor it may need a wire brush about foot or so long to thoroughly scrub any remaining blockage. If your inlet is covered by grid you may still have a problem forcing the blockage through .Finally purchase the correct gasket for your raw water pump make,then remove its faceplate to inspect for impeller failure and or renewal, and inspect the face plate for any excessive wear . Some faceplates are reversible or you could get it refaced .
I have very recently had a similar raw water failure and tackled it as above,fortunately the first step was sufficient to get the engine restarted and properly cooled but the heat exchanger also was topped up with fresh water before restarting, and later addng the correct antifreeze for the winter.I hope this is of some assistance.

ianat182