View Full Version : Should boat tach be checked with hand-held tach?

05-15-2010, 10:32 AM
Have Yanmar 4JH3-TE with about 350 hrs. Have type B panel. Max. rpms under load now is 3750 (max for engine acc. to Yanmar is 3800) according to boat tach. Not sure if this is close enough not to worry. I am not aware of any particular problems. Engine seems to idle best around 800 rpm (specs for engine are 700-725 rpms) or slightly lower. Is there a need to buy a hand-held tach and check the boat tach? If so, are the digital hand-held tachs that are priced around $30 worth it. Are the boat tachs (type B panel) reasonably accurate? Comments?



05-15-2010, 12:54 PM
I'm not sure what a type B panel is but the new digital instruments are extremely accurate, not so much so with the analog stuff. If you have access to a HH unit it is always a good idea to check it.

05-29-2010, 05:56 PM
I just finished checking the boat tach with a hand held tach. Looks like the hand held tach reads lower than the boat tach from idle up to max rpms. This was done in neutral. At 3800 rpms (boat tach), I got a reading of 3650 rpms with the hand held tach. Therefore, I need to gain about 200 rpms. This Fall, I will bring the prop in and have them reduce the pitch and gain 200 + rpms in order to achieve 3800 rpms under load.