That’s as straight forward as it gets – no graphs, no spreadsheets, no data to interpolate. On the mechanical engine it is one number you need to verify and verify it 100% – RPM at Wide Open Throttle (WOT).
But before you do that you need to be 100% certain of your actual rpm’s vs. what your helm gauges are reading. This is done with a handheld laser tach. Usually this is just done at the dock at idle, mid range and high rpm. However, if your engine room allows, the most accurate way to do this might be at the engine at WOT out at sea on the right day. Not as easy and may not be necessary but I recently inspected a set of 6BTA’s and the tachs were very erratic so taking the reading at one or two rpms and using the delta was not a close enough approach as the delta was not constant and it was just easier to do it on the run but we had the right folks and right conditions to do so. You don’t by chance have Aetna digitals as in my pic do you?
When you are out on that sea trial you need to be sure you have a clean or normal bottom, not a fouled bottom, and make the boat heavy. At least as heavy as you normally plan to use it – full fuel and water tanks, all the gear and all the persons. You can simulate some of this with garbage pails and/or coolers full of water.
These engines needs to be propped to make an honest 3-5% over rated rpm. Your rated rpm is 3,000.
So what do you have now for tachs and what WOT rpm are you seeing?
Let’s see a pic of your helm station. You may have tachs that can be calibrated.
You should also check your no load WOT (neutral at the dock with an engine that is up to temp, not cold) and on your engine that should be close to 3.400 rpms.
Spend time searching and reading here, a lot of this is covered but maybe more in dribs and drabs here and there, not all inclusive, so this was good…
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