Re: Universal M25 losing power
"Even with our engine looooong out of warranty Joe Joyce of Westerbeke flat out told me I was damaging my engine by running it 275-300 RPM off max rated with the prop we had. In the short time we ran the boat that way the soot on the transom was considerably more than with the right prop. I hauled the boat, sent the prop back and had it re-pitched. It now sings within 25-50 RPM of max rated just as it had for the previous 2700 hours.. "
The suggestion that you're going to damage an engine by loading it such that it will only reach 90% of max rpm does not stand up to scrutiny. This is a tractor engine!. I hope no-one will be connecting any kind of heavy load to their tractors.... last time I checked the manual for my diesel car, it did not forbid driving up gentle gradients.... or putting some luggage and passengers in the car.... or driving into a headwind...or just driving on the freeway in 6th gear.
If the Universal in my Bristol (3 bladed prop, only reaches 2400rpm) is being damaged, it's taking a while for that damage to make itself obvious... it's 28 years old, the hourmeter broke at 3700 hours years ago, and it shows no signs of wear.
Mechanical wear rises rapidly with rpm so the lower your cruising rpms, the better (with reason, of course).
Bristol 31.1, San Francisco Bay