Thread Tools Search this Thread Display Modes
Old 10-01-2017, 11:33 PM   #1
Senior Member
BrisHamish's Avatar
City: Brisbane
Vessel Name: Beluga
Vessel Model: Grand Banks 46eu 2006 hull#289
Join Date: Apr 2016
Posts: 207
Mystery regarding raw water on CAT C7s

Hi all,

I am on a mission to have a dry bilge. I am sort of winning the battle...

I have gotten rid of all the fresh water (it took many months to trace all the aircon units draining to the bilge...).

And now I am left with a small amount of raw water ingress. I assume it is coming from one or both of the raw water engine loops.

Engines are CAT C7s, 2006, 1400 hours. Always serviced by CAT annually. Aftercoolers are checked and good, raw water loops flushed with Rydlyme in Feb this year, all raw water hoses new this year in April. When I visually check the engines whilst idling at dock I cannot see any leaks...yet there are new crystal salt deposits under each engine after running out on the bay, plus a small amount of liquid saltwater.

Thoughts as to where or how to check next. Is there some sort of pressure test I could get done??

Thanks all,


BrisHamish is offline   Reply With Quote
Old 10-02-2017, 05:17 AM   #2
TF Site Team
Insequent's Avatar
City: Brisbane
Vessel Name: Insequent
Vessel Model: Ocean Alexander 50 Mk I
Join Date: Mar 2012
Posts: 3,291
Whenever I have had leaks I have always been able to trace back, and see the area of the engine where the leak is occurring by the white salt, or if longer term some vertigris. If your engines are spotlessly clean you may still be able to trace leaks by putting paper towel around potential suspects. This might include raw water pump and oil/transmission coolers, and exhaust mixer elbows. What puzzles me though is when you say under both engines.

Other seawater leak candidates are shaft packing glands and also rudder shafts. I tolerate some water ingress in the former rather than have the packing get too hot underway. Shaft glands may not drip at the dock, but allow water in when under way.

Insequent is offline   Reply With Quote
Old 10-02-2017, 06:02 AM   #3
Technical Guru
Ski in NC's Avatar
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,176
Check condensate drains from aftercoolers. A fair amount of condensation can drain depending on operating modes. And yes, check shaft seals, often they do not leak until you get to a certain rpm.
Ski in NC is offline   Reply With Quote
Old 10-02-2017, 06:51 AM   #4
High Wire's Avatar
City: Cape May, NJ and Englewood, FL
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 3,899
Salt spray from air intakes on the side of the hull?
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May NJ
High Wire is offline   Reply With Quote
Old 10-02-2017, 08:10 AM   #5
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 9,253
As a subset to Ski's suggestion -

Per chance the last time the after coolers were serviced the "0" rings were not installed properly allowing salt water to pass to the condensate drains. Cat after coolers can get problematic if not done right. Salt water check in oil?

Also, maybe the Ridlyme sat in system too long and ate away exhaust elbows that only show leakage at higher RPMs. Paper towels are your friend for locating water leaks.
sunchaser is offline   Reply With Quote
Old 10-02-2017, 10:40 PM   #6
Senior Member
BrisHamish's Avatar
City: Brisbane
Vessel Name: Beluga
Vessel Model: Grand Banks 46eu 2006 hull#289
Join Date: Apr 2016
Posts: 207
Thanks all for those helpful responses.

We ran both engines up to 2000 rpm today (about 50% load), had some well positioned (and secured) paper towels in place, and here are the results:
On port, at that higher rpm, there is a visible and reasonably significant leak from the main raw water hose basically in underneath the engine where it connects to the engine. One of the clamps had given up the ghost, and the second clamp wasn't much better either. Solution will be to replace all hose clamps on both engines.
On starboard it is more interesting. At higher rpm a faint salt mist eminates out from the mechanical seal on the Sherwood raw water pump, which explains why I find only salt crystals on that side (the mist itself evaporates from the engine heat, so by the time I dock and get down into the engine room there are only crystals left).

So all in all, nothing that $$ cant cure!!

Thanks again for your replies.


BrisHamish is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program

All times are GMT -5. The time now is 08:48 AM.

Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012