Draining the muffler before trailering D3 or D4

[BB marine]

After completing our trip and getting ready to tow the boat back to our Storage facility approx. 400 mile trip. I was going over my trailering checklist with an other Cutwater owner. He said he was told by his dealer that the muffler has to be drained for trailering to stop water from entering the exhaust manifold and turbo. I had never heard this before and questioned this. I have trailered the boat close to 2000 miles and never done this and had no problems. He said that the dealer told him if you hit the brakes hard the water can migrate up the exhaust and do damage to the turbo. "Salt water will take out the turbo " Statement made by his dealer. I took his word on this and drained the muffler before trailering back. The problem I see is the drain plug at the bottom of the muffler is a self tapping screw that screws into fiberglass. The fiberglass is thicker at the drain plug area but I fear over time this will not seal properly. If it is a necessity to drain the muffler I will figure out a way to install an true drain petcock in the base of the muffler instead of the self tapping screw. I'm looking for any comments or knowledge to this subject. Thank you in advance.
Brian Brown
26 Cutwater
PORT-A-GEE

 

[S. Todd]

My dealer never gave me these instructions for our D3 and I have been unable to find a drain plug on my muffler. Where is the drain plug located? Picture? Like you, I have trailered for about that many miles with no issues to date.

 

[BB marine]

Drain plug on my muffler is located right under the intake side of the muffler (where the exhaust goes in) below that there is a "nub" sticking out, below that is the drain plug. I used a 3/8 socket to remove it. I was never told about this either, that's what is nice about this forum someone will know the answer.
Brian Brown
26 Cutwater
PORT-A-GEE

 

[S. Todd]

Found it once you told me what I was looking for and where to find it. You are correct it sure does not look like a drain plug one should remove and replace on a regular basis.

 

[Brian B]

I would ask this question directly to the factory. If they do not know the answer they can go directly to Volvo.

 

[Andrew Custis]

I have never removed a plug on the muffler prior to trailering. There were some early models that we didn't adapt what we call a surge tube too which prevented this but they were all corrected. I would say that it doesn't hurt anything to remove the plug but certainly not necessary.

 

[BB marine]

Thank you Andrew for the response. I thought that what I call a Nub had a purpose, and figured the water would Flow in that before going up to and past the mixing elbow. I didn't know so I drained the muffler. If there is no issues, I'm not draining it.
Brian Brown
26 Cutwater
PORT-A-GEE