I need to calibrate my tachometer on my Yanmar 3JH3E.. What is the most inexpensive way to do this? I have been looking on line for a tool (tach gun etc) but I am not sure what I am looking for. Can anybody tell me the specific name of the piece of equipment to use? Thanks Brian s/v CREW REST
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Don't think that you can calibrate them.
Brian: I think that this has come up before. As I remember these tachs cannot be calibrated. You should contact a Yanmar mechanic or one of the Yanmar distributors and pose this question. They are usually off about 100-200 rpms. Why do you want to do this?
Brian: I think that this has come up before. As I remember these tachs cannot be calibrated. You should contact a Yanmar mechanic or one of the Yanmar distributors and pose this question. They are usually off about 100-200 rpms. Why do you want to do this?
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Brian C.
Because....
I changed props on the boat and shortly there after my RPM's dropped quite a bit. The prop manufacturer said he had put the same prop on the same boat with a much, much smaller drop in rpm's. He will be happy to adjust the prop, but he wants to make sure that the tach is accurate... The reason we have any doubt in the first place is because when the engine reaches it's max rpm of about 3200 (it is rated and used to do 3800 underway) It doesn't seem to be loading up (no black smoke) when the throttle is advanced further. (the throttle is advancing to the stop on the engine itself, and will advance normally when not under load) There was a span of about 2 weeks from running the boat with the old prop and running with the new prop.. I doubt that anything would have changed with the engine during that time, but I went ahead and changed filters etc to be sure, but no luck... Some options are having a diver take off the new prop, put on the old one, run it and see if it spools up like before, or getting a some sort of verification of my engine rpm's...Hence the question. I would bet the boat (not really) that the prop is over pitched, but the lack of black smoke has me at a loss.. Thanks, Brian
I changed props on the boat and shortly there after my RPM's dropped quite a bit. The prop manufacturer said he had put the same prop on the same boat with a much, much smaller drop in rpm's. He will be happy to adjust the prop, but he wants to make sure that the tach is accurate... The reason we have any doubt in the first place is because when the engine reaches it's max rpm of about 3200 (it is rated and used to do 3800 underway) It doesn't seem to be loading up (no black smoke) when the throttle is advanced further. (the throttle is advancing to the stop on the engine itself, and will advance normally when not under load) There was a span of about 2 weeks from running the boat with the old prop and running with the new prop.. I doubt that anything would have changed with the engine during that time, but I went ahead and changed filters etc to be sure, but no luck... Some options are having a diver take off the new prop, put on the old one, run it and see if it spools up like before, or getting a some sort of verification of my engine rpm's...Hence the question. I would bet the boat (not really) that the prop is over pitched, but the lack of black smoke has me at a loss.. Thanks, Brian
Oh
Brian: Ya, you don't want to bet the boat. The RPM's is a relative thing. If your relative RPM's was 3800 and now it 3200 then I would guess they need to take about 1-2 deg of pitch out of the prop. What prop did you have and what did you change to.
Brian: Ya, you don't want to bet the boat. The RPM's is a relative thing. If your relative RPM's was 3800 and now it 3200 then I would guess they need to take about 1-2 deg of pitch out of the prop. What prop did you have and what did you change to.
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Ron Mills
Steve is correct
The true Yanmar tachos do not have a calibration screw. I understand you can cut a hole in the back if you know where but the adjustment is minor. If you have one on the other aftermarket tachos you may be able to adjust. The 3JH has 114 teeth on the flywheel. I would suggest posing the question to Dick at Yanmarhelp link www.yanmarhelp.com
The true Yanmar tachos do not have a calibration screw. I understand you can cut a hole in the back if you know where but the adjustment is minor. If you have one on the other aftermarket tachos you may be able to adjust. The 3JH has 114 teeth on the flywheel. I would suggest posing the question to Dick at Yanmarhelp link www.yanmarhelp.com
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Brian C.
Thanks guys
I am pretty sure the pitch adjustment is gonna be the deal.. Just going to verify the RPM for the prop guys sake.. I switched to the Campbell Sailer prop. I am seeing more speed under sail with the prop and have been very happy with it except for the RPM issue. Thanks Brian
I am pretty sure the pitch adjustment is gonna be the deal.. Just going to verify the RPM for the prop guys sake.. I switched to the Campbell Sailer prop. I am seeing more speed under sail with the prop and have been very happy with it except for the RPM issue. Thanks Brian
This has been an issue before.
Brian: This has been an issue with them before. Check the archives.
Brian: This has been an issue with them before. Check the archives.
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Rich Wallace
Revolution Counter
When I was a kid my father had a little device that counted revolutions. I have looked for one for years but have not found one. Anyway, you held it against the end of the shaft (crankshaft) you were checking, and waited for a minute. The counter showed the RPM's. Even though the tack may be off, you would be able to set up a chart of indicated to actual. Sorry, I don't know where to find one of those devices.
When I was a kid my father had a little device that counted revolutions. I have looked for one for years but have not found one. Anyway, you held it against the end of the shaft (crankshaft) you were checking, and waited for a minute. The counter showed the RPM's. Even though the tack may be off, you would be able to set up a chart of indicated to actual. Sorry, I don't know where to find one of those devices.
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