Way back some place, Arl, you put your RPM at highway speeds as..hold on,gotta find it again...reply #22
"1. Is the ISB a 2-stroke? Why the high rpms? 3000? That sounds high, even for me, who is used to 2300 rpm cruising speed at 64mph. I thought THAT was high. The poor 8v71 sounds like its hurting itself."
With all the "chatter", everyone missed it. 2300 rpm at 64 mph doesn't sound right at all.
An MC9 with 3.7 differential gear should turn 2100 rpm at 70 mph.
Tachometer maybe out of whack...or?
As for noise, how is that getting into the coach? The access holes down the back properly sealed up? Muffler blown out?
And on the oil consumption, what oil are you using?
My low mileage 8V71 burned oil badly when I got it from the previous owner, as a hired hand had put 15W40 in it. After I changed it to low ash CF2 40wt, consumption pretty much vanished.
I'm partial to keeping my money and energy outputs to a minimum when possible. There may be simple solutions short of a re-power. And your fuel economy is good, so how much can be wrong?