03-31-2010 11:39 AM
I have twin 3126 350HP in my tiara
I now have 1600 hrs on them
over the past year i have had problems with a small to moderate amount of steam in the wet exhaust that dissipates within 2-5 seconds
it occurs more often when the engines are working hard (80% of power 2250rpm/ pulling jetski/ full fuel tanks ect)
engine temps are always unchanged right at 185 as they have always been once engines are warmed up
the boat tends to burn through impellers ( as a result of being in our socal kelp beds) and that is always the first thing i check and replace
but i am wondering if i am missing something else like maybe the oil coolers or heat exchanger needs to be boiled out?
I have never serviced the heat exchangers or oil coolers since i bought the boat 1100 hrs ago (4 yrs)
again steam is with normal engine temps
03-31-2010 11:31 PM
could you noticed a water flow decreasing at the wet exhaust ? Many time the cause of failure is at the strainer itself or entry of the blocking valve , the one you close to service the pump . Other thing could be a restriction in the raiser , this reduce the amount of water to cool the exhaust , as result the exhaust temp keep high enough to steam more water than normal.
04-09-2010 05:44 AM
It would be advisable to clean your raw water cooling system after each impeller failure as debris goes through the system and tends to block the faces of the coolers. This can lead to poor water flow through the engine resulting in higher exhaust temperatures. This is a common problem following impeller failures.
04-28-2010 12:03 PM
Thanks for your suggestions
i had the transmission oil coolers boiled out the heat exchangers are clean the impellers are intact the raw water strainers are clean and all the hoses were back flushed
and i still have steam
i spoke to another mechanic that suggested the exhaust risers could be plugged with an impeller blade or have similar scaling deposits so that is the next thing that i will look at