8V71TI steam/smoking problem

[oldhatt]

I have a problem that I have been chasing around for a couple of weeks, and I now feel that I am going in circles. Anyone have suggestions.
My starboard engine in our 1975 45-C starts and runs fine. The boat stayed at the dock for three months as we spent most of our time reparing huricane damage to the house. A couple of weeks ago we took her out for a run, and I noticed some white smoke or steam from the exaust. Also at anything over 1800 rpms the temp would start to creap up. Engines usually run @ around 175. I cleaned the cooling system using the phiosophoric flush method for a couple of hours. This worked great and stopped any heating problem. Now exhausts are clear up to 1900rpms. Anything over that I start to see steam or white smoke. This increases with rpms, but the temp holds steady under 180. The temp of this engine falls rapidly when rpms redused to 1000. 150 degrees. The smoke goes away all most immediately when rpms reduced to 1800 or lower. I feel that this is steam as it dissapates all most immediately, within 15 feet of the boat and I see no haze behind us.
Any ideas?

 

[Genesis]

If the temperature is normal on the engines it may just be atmospheric conditions and of no consequence.

If not, then you have to find the restriction in raw water flow. There is one, and its findable - but you may have 'fun' locating it.

While you're at it take an IR thermometer and shoot the elbows post water-injection, along with the hose connections. Report back here with the temps so we can tell if you have a real problem or are chasing your tail....

 

[Nonchalant1]

You can tell steam from smoke by the way it dissapates in the air without hanging around much. Smoke hangs or blows in the air.
On my inboard gas engine ski boat, it steams before it overheats when there's a restriction in the incoming raw water system. Maybe you have enough raw water running to cool the heat exchanger, but not enough going through the "shower head" inlet for raw water into the exhaust system. The hot exhaust is converting it to steam too much. If so, check for a plugged shower head, after you've checked the likely suspects like raw water impeller blades stuck in the raw water pipes, bad or partially closed seacock, etc.

Doug

 

[oldhatt]

Well, it took me a while to get this done, and I probably have too much info, but here goes.
Running the engines @ 1900rpm bay water temp 75 deg. Taking readings with an IR gauge Raw water temps.
bronze thru hull valve 90
jabsco pump, in side 101
" out side 104
stb side intercooler in 122
" out 103
port side intercooler in 111
" out 96
pipe to fuel cooler 95
fuel cooler [ locater over exhaust manafold] 137

pipe comming in to heat exchanger 92
pipe going out of heat exchanger 120
metal tee dividing water flow between
each side of exhaust 106
stb side exhaust at turbo 144
port side " 127
stb side shwr head 112
port " 115
Fresh water temps.
stb side t'stat housing top half 184
" bottom half 179
top pipe into heat. exc. 180
bottom pipe into heat exchanger 168
top water out of heat exchanger 182


bottom water out of heat exchanger,
"J" pipe to water pump 180

This engine is producing steam out of the exaust at thest temps.
Any ideas?
I have now discovered that there is visibally less water flow from the exhaust of this engine than the other.
Have flushed the raw water side, changed the impeller, and had the through hull strainer cleaned.


Any help and advice appreciated.
Safe Boating
Sam

 

[Genesis]

Get under the boat and see if there's a restriction in the through-hull.

This may require removing the clamshell, which is loads of fun to do in the water.

 

[divert00]

Similar difference in raw water outflow and steam on lower flow engine on my 1979 43C with 6v92s. Found oysters love my raw water intakes (inside of the clamshell cover). But item that cured was cleaning exhaust showerhead; it was about 25% blocked. Not difficult, but a 2 man job to handle large SS Y-shaped exhaust manifold.

 

[oldhatt]

Well,
Thanks to all for your input. The problem is now solved. Had the through hull strainers cleaned. They were partially blocked. That did not solve the steam. On the KISS theory decided to go back to the pump. Took the pump off , opened it and found no real problem. Bearings and seals good and working. BUT, several small problems. Slight cam wear. Same with cover and wear plate. Also impeller did not seem to be wearing evenly. Bottom line, The nice people at Fl. Detroit Diesel in Ft. Myers gave me a great price on a new pump, Got it installed, and the problem is solved. I guess that 30 years of service life is enough for the pump body to just wear out.
Thank you all again for the input.
Safe Boating
Sam