Dee and I just returned from two weeks on our Bristol 29.9 cruising the coast of
Maine. I am happy to report that our little
Yanmar SB12 is running perfectly. The modifications that I made to the
fuel system are also working well. There were no air
leaks and no
fuel leaks. The
engine starts on the first rotation every time. We even had a situation with a low
battery (different story) and could just get the
engine to barely turn over. One
compression cycle and it was running!
I watched the
oil use carefully. Though the
oil consumption is way down from where it was before the
rebuild, the engine is still using some oil. Last year, before the
rebuild, it was using about 5 ounces of oil an hour. In the first thirty hours of operation after the rebuild, the engine used a bit less than a pint of oil. This equates to about 0.48 ounces per hour. In the next twenty hours of operation, the engine again used about a pint of oil, which equates to about 0.74 ounces per hour. In that twenty hour period, ten hours were spent trying to keep up with another, faster
boat. We ran the engine at a steady 2,850
rpm. Normally we keep the engine at about 2,600 to 2,750 where it is much quieter. At 2,800
rpm and above every bolt and bulkhead on the
boat vibrates and resonates. It's quite a cacophony of sound! But, this higher speed use may account for the increased oil use.
Does anyone understand the governor mechanism on this engine? If I put the throttle all the way forward, the engine goes to 3,000 rpm but settles back to 2,850. It then hunts a bit between 2,800 and 2,850. As noted, I don't like to run the
motor at it highest possible speed, but I'd like to know what keeps bringing the speed down from 3,000 to 2,850.