Am I missing anything that could be bringing water into the double hull?

[FSH 210 Sport]

So if I understand this correctly, you had a new transducer installed and the installers removed the clean out tray to gain access to that area where the transducer wires come through, that would explain the dislodged clean out plug. I’m going to guess that they left the the drain line off of the clean out tray that goes from the clean out tray to the bottom of the swim step above the jet pump where it mounts to the transom. This could easily be forgotten when re installing the clean out tray.

Pull the mechanical access hatch off and reach down under the clean out tray and make sure this 3/4” drain line is attached.

The next thing after that is to seal up the clean out tray while it is installed.

I’m also assuming that there was no such leakage before the new transducer was installed.

 

[MilesPrower]

I’m going to guess that they left the the drain line off of the clean out tray that goes from the clean out tray to the bottom of the swim step above the jet pump where it mounts to the transom.

I was going to same the say thing.

BTW, even after you re-install the drain line to its corresponding fitting in the cleanout tray, that drain line will still lead to a ton of water landing in your bilge. When you're running the boat, water comes up that drain line and spills into the cleanout area. When enough water gets in, the little hatch between the cleanout ports has no chance of preventing water from falling into the bilge.

Three things that will help:

1. Seal the edges of the whole cleanout tray, as @FSH 210 Sport has already mentioned.

2. Mount an inline one-way float valve in that drain line to prevent water from being pushed up and into the cleanout area.

3. Install a cleanout hatch riser:

Yamaha Mechanical Access Port Riser

Add vertical height to the location of your clean out port compartment's mechanical access port. Adding this custom "STARBOARD" CNC fabricated riser will raise your boat's mechanical access port 3/4" above the deck. Raising the access port up off the deck has the effect of keeping the bilge...

jetboatpilot.com