|Posted: September 25 2008 at 11:41 | IP Logged
If that's all you changed and the rpm specs changed after tab removal, then I would say the trim tabs are the cause. I could see the lowered RPMs at WOT if the boat is not planing, but it could be other factors. Did you have spec WOT RPMs before removing the trim tabs? If so, go new trim tabs.
I have trim tabs on my boat and I can plane with then up, but it just takes longer to do so. Your hull is different than mine, so I can't say for sure, but I would think that it should plane without them. Trim tabs are not the only dynamic in performance. This and the difference between the engines could be due to linkage adjustment or prop, shaft, and strut issues.
I have a Carver 3207 with 270hp Crusaders and had the same problem with reaching full RPM @ WOT. My primary problem was in the props. Previous owner replaced both props after a foul with a chain. The replacements had same size and pitch, but a larger blade area than the originals, so held the water longer (more work for the engines) which lowered the WOT RPMs. I had the props scoped, tuned, and resized 1/2 inch shorter (total circumference) and that got me back on spec. I still had a difference between engines that went away with truing the lower RPM engine's prop shaft (slightly bent) and re-aligning both engines. Now I'm pretty close (maybe I'll fiddle with the linkage next).
If everything else is running well, props improperly sized or shaped, or props, shafts, or struts out of true could be culprets. And variation between the two sides on these factors can be the reason for RPM differences.
If they haven't been checked off the boat in a while, it might be best to have your props scoped by a good computerized analysis (just becaust it's time) and trued if needed this off season.
"It's always sumthin', ain't it?!!"