Yes, The replacement of the18 X12 is not bad at all. I purchased the west system
https://www.amazon.com/WEST-SYSTEM-105- ... 49&sr=8-21
removed the old tabs, cleaned the service area, fliled the mounting holes for the 12 X12 planes with the West system epoxy thickened to a paste. I use the hinge bracket as a template and drilled new holes and installed the new 18 X 12. Note
🙁 this proved to be an interesting find, when the installing technician at the factory installed the trim tabs he failed to install the tabs at Bennett's recommended hight. The planes were installed to high. The other issue I found, two of the mounting screws had the screw heads broke off. I assume when the technician was installing the screws the holes were not drilled large enough and it snapped the heads off (2 of them) Then it looks like he/she tried to screw another screw into the transom right next to the broken screw and snapped that head off too. I believe he gave up and used the sealant applied to the plane bracket hinge to hold the screw head in place.
Bennett's specification is 1/4" above the bottom of the boat. This photo show the installation 5/8" above the bottom of the boat. This reduces the performance of the 12X12 factory installed plane by 20%.
This shows the epoxy repair made. The two repairs shown are the ones I made at the broken screw heads at each location. You can see the two screw holes at each location where the screws were broken off, side by side. I was able to drill the broken screws out to make a proper repair using the west system epoxy.After repairing the two broken screw holes I proceeded to fill all the holes in the same way and then drill new screw holes for the new 18 X 12 planes. The point of this description is to tell you don't be afraid to drill new holes and mount larger planes. You would probably do a better job than the factory installer did on my boat. In my case removing and installing new tab planes corrected a factory flaw and gave me a better than factory install.
I'm not sure that the drop fin is causing the issue with the lack of thrust to the aft starboard. I talked to another Cutwater C28 owner about this. The proof the theory I removed the drop fins and tested the thrust change. There was no difference. There is a difference between starboard thrust and port thrust. The difference is the location of the thruster. The trim tab is reducing the thrust. 50% of the water flow is hitting the top of the tab. The 12 X12 with drop fin will have less effect than the 18 X 12 because the top of the 18 X 12 has more surface area to block the flow. I did notice less thrust to starboard after installing the 18 X12 but not enough to worry about.
This photo shows the thruster location in relationship to the trim tab. I believe with the tab fully retracted 50% of the thrust hits the top of the plane. If the plane is in the full down position the trust is effected even more. I alway make sure I have the tabs in the full up position when docking. If the Planes are in the full down position when backing down and using the thruster too, there is a lot of pressure applied to the top of the plane and could cause the mounting hinge pin or bracket to break.
