Raw water cooled exhaust - required...

[wingless]

Raw water cooled exhaust - required inspections

These are the required inspections for boats like mine, that were built w/ raw water cooled exhaust and operated in salt water. My 2000 380DA w/ 454 MAG MPI Horizon engines had many undocumented maintenance requirements to ensure proper operation, that took me years to understand, then effect appropriate solutions.

There are many owners discarding engines because the raw water exhaust has not been properly maintained. Those failures should be prevented.

Hand Hold Test - It should be possible to continuously hold the exhaust elbows w/ the engine running at normal operating temperature. Excessive temperature is indicative of internal corrosion. This is the fastest and easiest test. I perform this at every usage.

Disassembly Inspection - Remove the elbow(s) for internal raw water passage inspection. There should be minimal corrosion. The SOLID wall thickness between raw water passages and the central exhaust gas passage MUST be sufficiently thick to prevent water ingress into the exhaust. Do NOT be fooled by metal of the correct thickness that is not solid, that has deteriorated and detached from the casting. A dead giveaway is a shadow surface appearance on the cleaned gasket surface. The same inspection may be performed between the riser and the exhaust manifold. Note that new gaskets are required for reassembly. It is good practice to stock a pile of the correct elbow / riser gaskets and to perform this disassembly inspection on an annual basis.

Raw Water Hose Inspection - The raw water hoses feeding the bottoms of the exhaust manifold should be supple, like a car radiator hose. It should be possible to pinch and flex the hose. It should not be hard. It should not have a stiff crunchy feel when pinched.

Side Hull Exhaust Port - The above water side hull exhaust port should not be rust stained after operating the engines. This is an EASY dead giveaway of raw water cooled exhaust problems.

Failure of any of these inspections is indicative of a significant problem requiring immediate attention. The risk from these symptoms is total engine failure.

I would love to have a discussion w/ the Mercruiser engineer who thought running salt water through cast iron was a good idea, Same meeting for designing / supplying engines that are impossible to drain, impossible to flush, that retain salt water 24/7/365.

My obscenely expensive OEM exhaust components would last for 3-5 years before requiring replacement.

At the last replacement cycle, over four years ago, I had enough. I redesigned my exhaust system, so now I can drain, flush w/ fresh water, soapy water, Salt Away, then drain bone dry until next usage. The boat is wet-stored and is operated w/ all UL-certified OEM parts, no kludge plumbing or modifications that can silently fail, sending the boat to the bottom.

[wingless]

At my last disassembly for internal raw water passage inspection, after four years of service, the internal passages still look new.

My guess is that these exhaust parts will now last the life of the engines.

[RaceCarRich]

How about posting some pics or diagrams of your design?

[Burntundra]

I have your exact boat wingless, a 2000 380DA. You are privy to my engine problems from another post. I too am interested in your flush solution! I will have an opportunity to modify my exhaust while my boat is out of the water next month.

[Smils]

Hi Wingless, very clever of you to sort the corroding manifolds. Also very decent of you to share the info. Like to ask why the soapy water between flushing and Salt Away? Thanks,
smils

[Chris-380]

bump, this would be great info, i would like to move my boat to salt, but before doing so i need to upgrade to what you have figured out....

[gregk]

I am in salt water with a raw water cooled 2003 350 Mag engine and use the Perko inline flush kit and use the salt away mixer every time I get back to the dock. I get 8-10 years out of exhaust manifold, risers, and elbows with with the dry joint system.