Originally Posted by joemac4sail
I'm curious, what type of boat do you have. Its just that running at 3000 continuously seems high and usually for very little gain. Joe
I can tell you about my engine
. It's a new diesel
-- a Yanmar 3gm
The instructions (and the tech who installed it) BOTH say to break the engine in at HIGH RPM and to run it HIGH, not low. It's not good for diesels to run them below their optimal cruising RPM. For my engine, that IS ... 3000 RPM. If I'm running it all day I'm supposed to run it at 3200 for an hour or so. The manual couldn't be more clear.
However, because of a fouled tank, if I run it at 3000 RPM, the suction is enough to clog the screen
. Then the engine dies. The last time I limped in, we sailed as far as we could, started the engine and ran her at 2000 RPM up to the bridge, and then goosed her up to 3000 to go under the bridge.
The engine died before we were completely through the bridge. We thought that might happen and someone was on the bow ready to drop anchor
We sat at anchor
for a while, let the clump of whatever free itself from the screen, and then limped back to home at 2000 rpm.
The boat will not be used again until I have cleaned the tank, and then I will follow Yanmar's instructions and run that engine at 3000, and occasionally 3200, RPM.
I know someone who did a lot of damage to his diesel by idling it way too much. He would do this to charge his batteries when there wasn't enough sun for his solar panels
to do the job. at 2 years 5 mo. the engine threw a rod. The mechanic/tech told him that the thrown rod was the LAST bit of damage done, that he almost certainly had a variety of other damage done to the engine including burnt rings and scored pistons.
I had lots of people tell me that I'm running my engine too high, but it's my warranty, not theirs. They all have older engines and probably haven't looked at the manual in years.
And, by the way, with the right prop, for me, there IS a significant gain in speed at 2500 compared to 3000.
One thing that I have noticed with my fuel problem is that I had less power at the lower RPM's as well since it developed. Unless you're being fanatical about paying attention to RPM to speed to conditions (wind on the nose, current
with you or against you, etc.) these variances can be explained way and go unnoticed. "You had less speed? You *probably* had a current against you."
You can damage your engine without it overheating
an without an oil
pressure problem by running it too long, too slow.