How Do I Know If My Boat Is Too Noisy
  • If you drive by at speed, 200 feet from shore or more, and people sitting on shore find it hard to hear each other, or have to raise their voices to be heard, then your boat probably does not meet the proposed decibel limits.
  • If you have through the hull exhausts without any muffler, then your boat is illegal today.
  • If you have through the hull exhausts with mufflers but do not meet the first point or the proposed dB limits.
  • You can use a decibel meter to measure the sound pressure of your boat.
    • SAE J2005 – Standstill: Proposed limit is 88 dB(AS) three feet behind your transom at idle.
    • SAE J1970 – Pass-by: Proposed limit is 75 dB(AS) at pass-by at any distance, measured from shore.
How Do I Make My Boat Quiet Enough to Meet Proposed Legislation
  • If you have a Captains Choice, have it permanently disengaged ie. on quiet mode
  • If you have through the hull exhaust you have a few options:
    • Install mufflers either inside the engine box or on the pipe externally. This may or may not be effective enough to meet the standards. Large capacity engines and twin engines may be problematic. Costs for this range from $500 to $1500 per engine and may be able to be done without a mechanic.
    • Change the risers on your manifold so that the exhaust is directed via the out-drive to exit through the prop or below the water line when traveling at speed. Costs can vary significantly depending on the current configuration of your engine and exhaust.
  • There may be some boats that are designed as racing boats/ocean racers that cannot be adapted to comply. These boats are not legal today on smaller inland waterways, but can be operated 5 nautical miles from land, typically in the Great Lakes.
Products Available to Help Muffle Boat Noise

Gibson Performance makes mufflers that attach to the pipe as it exits the transom. They are tested up to 1,200 HP with minimal or no power loss and the vendor warrants that they will make your boat compliant with SAE J2005 at 88 dB(AS).

Harden Marine makes mufflers and bypass systems designed to reduce decibels.

Clamp on silencers

In-line silencers

Exhaust Diverters (Captains Choice)

Pictures of Various Exhaust and Muffler Systems

Captains Choice installed in a Donzi

Merc Stern Drive Engine with “through-the-prop” muffler

High performance racing engine without through-the-prop configuration. Note: there is no capability to divert the pipe to through-the-prop.

Note: there is no capability to divert the pipe to through-the-prop.

Gibson High Performance Bullet Muffler installed. The manufacturer warrants that this will make your boat comply with SAE J2005 – 88 dBA decibel reading