Getting ready to install an Airmar R199 "tub" and a Garmin GT51M-TH thruhull. The R199 is a 2kw shoot thru connecting to a GSD-24
R199 tub is going stbd side where an oil tank used to be. Cut the shelf out and ground down the hull. There were some air bubbles between the hull and the stringer tabbing.
This is going in with 5200 and maybe some epoxy puddy. It is really heavy so it needs a strong bond and it has to hold propylene glycol.
In this pic you see the centerline 2" hole from a removed B744. I will have to patch that and redrill a 1" hole for the GT51. Normally you would feather out the hole 12" x 1/2" deep but I have thru hull valves in the way and I'm going right over the patch with a bolted transducer. I'm going to do minimal taper inside and out, then span the area with a 1/4" flat fiberglass mounting "pad" inside & out ( like a homemade fairing). This "sandwich" with the transducer squeezing it will compensate for not doing the full feathered patch.
I can't decide the positioning of the GT51. A forward position would drill the new 1" hole thru existing hull...or I could position it further aft and drill the new 1" hole thru the 2" patch. Either way the patch is covered by the tranducer.
Edit:
Here is a full thread on the Shoot thru project.....
Shoot-thru tub in 265express?