Last Spring when I purchased my 1996 C-30, the surveyor was able to get a maximum RPM of 2900 on the Universal M25 engine. He indicated that given the age and hours (1000 hours) 2900 rpm is quite normal. My first question is: Since this is lower than the specd RPM, what should my normal cruising rpm be? The second question has to do with the Tachometer. At the survey it registered 1900 rpm when the engine was running at 2900. What is involved in getting the tach calibrated or replaced?
Engine Speed
- Thread starter Mikes Oasis
- Start date
- Status
These Tachs are notorious for unreliability,
and most of us are dubious re: their accuracy. We used to calibrate electric tachs on big diesels by comparing them to a calibrated hand tach that we placed on a mechanical drive off the engine at 1/2 crankspeed provided for the purpose. I am not aware of any similar method for doing our tachs on small engines. Mine is more reliable if I remember to wait a second after I pull fuel shut off before turning off key to allow needle to return to 0. Hope somebody can shade more light then me. I motor at what seems like ~ 80% of full thottle as a max, regardless of what actual numbers on tach read.
and most of us are dubious re: their accuracy. We used to calibrate electric tachs on big diesels by comparing them to a calibrated hand tach that we placed on a mechanical drive off the engine at 1/2 crankspeed provided for the purpose. I am not aware of any similar method for doing our tachs on small engines. Mine is more reliable if I remember to wait a second after I pull fuel shut off before turning off key to allow needle to return to 0. Hope somebody can shade more light then me. I motor at what seems like ~ 80% of full thottle as a max, regardless of what actual numbers on tach read.
It doesn't matter
The tach runs off the alternator, not the engine. It all becomes relative. Try the teleflex website to find out about setting the tach with the adjustments on the back. This is a very common issue, and there's tons of stuff on this site's forum archive (try "teleflex") and any other website for Catalina's with Universal engines, so also try the C30, C34 and C36 websites. Stu
The tach runs off the alternator, not the engine. It all becomes relative. Try the teleflex website to find out about setting the tach with the adjustments on the back. This is a very common issue, and there's tons of stuff on this site's forum archive (try "teleflex") and any other website for Catalina's with Universal engines, so also try the C30, C34 and C36 websites. Stu
Tachs
I agree that the tachs on these boats are not accurate...check the owner's forum: http://www.catalina30.com/
I agree that the tachs on these boats are not accurate...check the owner's forum: http://www.catalina30.com/
Calibrating tach
I had my Teleflex tach calibrated about 4 years ago. When I bought the boat, the tach would read about 2000 rpm when the throttle was pushed to the pins. At first, I thought it was an engine throttle problem, but decided to have the tach checked. I had my mechanic check it out, and the tach was off significantly. As I recall, there is a series of pins inside the Teleflex tach. Depending upon your engine/alternator combination, the pins are set to a particular combination. If one or more is in the wrong position, you will get an inaccurate reading. After calibrating, the tach reads properly, and my max indicated rpm is about 3200. I cruise any where from 1800 to 2600, depending upon conditions, desired speed, etc. A good mechanic should be able to do this in an hour, perhaps less. I did not attempt it myself since I did not have the timing light, or the manual showing the pin positions. Good luck. Randy
I had my Teleflex tach calibrated about 4 years ago. When I bought the boat, the tach would read about 2000 rpm when the throttle was pushed to the pins. At first, I thought it was an engine throttle problem, but decided to have the tach checked. I had my mechanic check it out, and the tach was off significantly. As I recall, there is a series of pins inside the Teleflex tach. Depending upon your engine/alternator combination, the pins are set to a particular combination. If one or more is in the wrong position, you will get an inaccurate reading. After calibrating, the tach reads properly, and my max indicated rpm is about 3200. I cruise any where from 1800 to 2600, depending upon conditions, desired speed, etc. A good mechanic should be able to do this in an hour, perhaps less. I did not attempt it myself since I did not have the timing light, or the manual showing the pin positions. Good luck. Randy
Tach Calibration
The Teleflex tach's have an internal adjustment based upon the number of "poles" in your alternator. The Tach directions explain the calibration and you can check your engine manual or manufacturer for the pole count. The following DIY tach calibration method really works. Tachometer Timing: Place strip of white tape near outer edge of the face of the crankshaft pulley. Shine a shore powered (60 cycle AC) fluorescent lamp on the pulley with engine running. At 1,800 RPM you should see four steady, stable tape marks hovering at 90 degrees from each other. Adjust Tach. At 3,600 RPM (if your engine can get that high)there will be two steady marks hovering at 180 degrees from each other.
The Teleflex tach's have an internal adjustment based upon the number of "poles" in your alternator. The Tach directions explain the calibration and you can check your engine manual or manufacturer for the pole count. The following DIY tach calibration method really works. Tachometer Timing: Place strip of white tape near outer edge of the face of the crankshaft pulley. Shine a shore powered (60 cycle AC) fluorescent lamp on the pulley with engine running. At 1,800 RPM you should see four steady, stable tape marks hovering at 90 degrees from each other. Adjust Tach. At 3,600 RPM (if your engine can get that high)there will be two steady marks hovering at 180 degrees from each other.
It's a lot easier
to do if you just run the engine (in neutral) to max revs. Make that 3,000 rpm on your tach. You are done. No need to measure anything. Stu
to do if you just run the engine (in neutral) to max revs. Make that 3,000 rpm on your tach. You are done. No need to measure anything. Stu
- Status