280 verses 260 for recreational use

[Jay Smith]

I build tons of both.. The stock ROS 280 is a torque beast but will not turn the RPM's because of weak ignition and a 1.625" port height verses the 260 thats 1.565" port height. The reason the low port height on the 280 is that LOW is Mercury wanted to make but one 2.5 block and with the chest removed from the Drag/F1 type blocks it had NO torque on the bottom with recreational pump gas heads thus they found the torque the Drag didn't have with pump gas compression by lowering the port mappings... Both are great motors , I am building 3 260's and 1 280 in the shop now as well as 2 225 Pro Max's .. IMO the ROS 280 is hard to beat IF you do the proper maintenance, use premium oils and clean high test fuels as well as have the correct pistons clearances and parts installed at rebuilds.. I am getting GOOD leak down % with Wizard Pistons with TiN rings until 120-140 hours on my 280 rebuilds and mods after I hone them and start off with a bore that is with in 1/2 a thou. being perfectly round at the rebuild. If the bores are not within that spec I can bend them to that tolerance and have a great seal and leak down through out the run cycle, I find that the .006" spec that Mercury claims to be run able at the high side of THEIR tolerance is beyond STUPID and the motor will NEVER seal nor make power.. Motors can only make their utmost power with round holes and round pistons with the correct piston manufacturers clearances and piston ring end gaps.

The charging system on the 280 FAR out performs the 16 amp 260 style charging system. A fully charged battery on a 260 at the lake running with the fuel pump, trim and engine running voltage draws will only perform to top potential no more than 3 to 4 hours continious running, every 260 I build I check on my run stand before I ship and with a HOT 12.75 volt charged battery checking with a fluke meter will at 1500 to 2000 rpms only yield 13.5 to 13.8 volts FAR short of what the demands of the motor trim and fuel pump demands thats even with the voltage regulator removed, and if there are other draws on the voltage systems such as a radio its gets even shorter run times before a lack luster performance can be felt at the end of the run cycle..

Peace
Jay