We extend to you a cordial "WELCOME ABOARD !" Come on in, make yourself at home, we are a friendly group of enthusiasts, and we also appreciate the classic Chris Craft Roamer, Corsair, and Lancer boats too , as they are all on the same family tree and share much in common !
It's great to see another 27' commander in the forum! I also have a 27' commander (see linked thread above) that I picked up a few years back. It has been great fun for me and the family. The folks in this forum have been tremendously helpful (and entertaining) with these boats and provide fantastic ideas and insight when asked.
These boats are great but - I too like to get some speed out of it on occasion. We are located on the coast just north of Boston where not only are the car drivers rude and crazy but the boat drivers are too. We had upgraded to the CC from an 18' ski type boat from my younger days to better fit the family (now of 5). My first ski boat was a Glastron Carlson CVX16 150HP O/B and I could get about 50 MPH out of it all trimmed out and skipping on a few inches of the hull in the water (like a potato chip with a motor). More recently we had an 18' Regal 3.0L I/O would get about 35 MPH.
I have seen my 27' Commander at 30 but only under perfect conditions and WOT of 4000+RPM. It has a 327F, 1.5:1tranny, 15x16 prop. I would love to be able to run 25 all day and 35+ on demand. Although not realistic with the current setup; I can easily over-rev the 327 leaving me thinking I can try another notch or two up on my prop pitch to squeak another MPH or two. I have been keeping an eye out for a 15x17 or 15x18 prop to try out. Even if I get more speed it'll only make me want more again. Maybe when I blow my motor I can try a big-block & 1:1 tranny combo to get my prop RPMs up and see some more speed.... even then I'm not sure the numbers work out - now I'm really talking crazy.
All that ranting aside what is your speed and RPM at WOT now? I'm not sure that you'll get 30MPH @ 3500RPM with your current setup but in my experience you should get 25MPH in decent conditions (flat water) at 3500RPM. My 27 starts to feel real nice at about 19MPH @ 3000RPM and keeps feeling better all the way till WOT - then it sound great too!!
I agree with Paul on the trim tabs - the only reason I would go with them is to bring your bow down when you are plowing or to adjust for uneven weight distribution.
Regarding the transducer, I am installing one this spring as well. I upgraded my hand held GPS (seen in the video from the linked thread above) to a Garmin 541s. I agree with Paul on the transducer and opted for a Airmar B117 bronze thru hull model. From my research, I am hearing that these types when installed properly do not experience the underway accuracy issues often seen with the transom mount models. I would love to know where others have mounted their thru hull transducers if anyone has done so in a commander??
Below are a couple of pics and vids of great times and memories from last season - I can't wait to get back in the water!