Tachometer replacement

[JD-MDR]

Can anyone recommend what tach I should get to replace mine." VDO" brand looks like 3-1/8" and goes to 3000 rpm. There are 4 wire connections . There are so many tach online I don't know what to get. The motor is MD7A. I had a mechanic come down to check my engine problems. He thinks the tachometer isn't working it seems to go up to 1700 and doesn't go any further. I thought I just wasn't getting power. Because of the smoke we sent the injectors in. I already did everything recommended by you all. From draining and cleaning the fuel tank and lines to cleaning the exhaust and flushing the cooling system. Thanks

[Jim Walsh]

Readily available direct replacements. Just choose a clone of what you have presently. Available here and at many other outlets I presume.
https://search.defender.com/?expression ... Trigger=ac

[Jeff and Sarah]

A different option that can serve as a back-up if your existing tach is actually still working:

https://www.tinytach.com/diesel-tinytach

It uses a transducer on your fuel line. I've never tried one of these but I've often considered ordering one to have a tach reading at my helm (which isn't critical but seems more useful than tucked away in a spot hard to see near the cockpit sole).

[Steve Laume]

Any good mechanic should have something like this kicking around his shop. https://www.harborfreight.com/digital-p ... 66632.html
Maybe not one this cheap but a way of checking to make sure the tach is correct. For less than $40.00 you could order this one to find out if it is indeed a problem with the tach or the engine is not cranking any faster than it says. My surveyor had one when he checked out Raven way back when I purchased her.

I did replace my tach when it started to read erratically. Mine was driven by the alt and was pretty simple to swap out. Any tach that is rated for a diesel engine should work. I like the analog read out as it gives you an instant idea of what the engine is doing, Steve.

[s2sailorlis]

Just be suspect with HF tools in general. Typically if it has moving parts they tend to break. If they involve electronics they tend to behave erratically. I've gone thru several meters and sensors and tachs that were plain rubbish. I did but a an infrared thermometer that does seem to work ok.

My general rule with HF is less moving parts the better!

Any good mechanic should have something like this kicking around his shop. https://www.harborfreight.com/digital-p ... 66632.html
Maybe not one this cheap but a way of checking to make sure the tach is correct. For less than $40.00 you could order this one to find out if it is indeed a problem with the tach or the engine is not cranking any faster than it says. My surveyor had one when he checked out Raven way back when I purchased her.

I did replace my tach when it started to read erratically. Mine was driven by the alt and was pretty simple to swap out. Any tach that is rated for a diesel engine should work. I like the analog read out as it gives you an instant idea of what the engine is doing, Steve.

[Sea Hunt Video]

Anyone care to guess where 98% of the stuff Harbor Freight sells is mfg.

[JD-MDR]

Hi Roberto, Chicago brand tools are probably Chinese I guess, I buy them sometimes. I call them disposable. sometimes I need something that I know I will never use again. Once in a while I get lucky. The belt sander didnt last long but the cheap demo hammer is Ok for removing tiles. Suprisingly the free voltmeter they gave me has been usefull for a few years

[Steve Laume]

I posted the hand held tach as an example of what would be needed to check the accuracy of the one that is suspect. In this instance a cheap throw away unit would be all you need for a one time use. I am sure it would do the job. If it is an ethical issue, then good luck eliminating all Chinese products from your life.

I don't buy much from HF but I did pick up a cement mixer from them last fall as I have one project I need it for. I am sure it has a Chinese motor that will fail in time but it just doesn't matter in some cases.

If you were a professional diesel mechanic you would be wise to invest in a better unit. In this case the throw away would do the job. I hate to borrow stuff but that would be another option, if you knew someone who had the tool. A third option would be to just change out what could be the perfectly functioning, existing tach.

I am a bit surprised the mechanic didn't do this check, Steve.

[JD-MDR]

The certified Volvo mechanic was confident the tach is bad . He dollied my outboard down the first trip and didn't need to go back for tools .He will be back to install the injectors and do a compression test and he will have his tach. @ $135 an HR it's probably 35 ea trip up to the truck.I guess with the smoke it was obvious I need to service the injectors considering I already did everything suggested

[JD-MDR]

There was too many variables to install a new tach and I don't want any more gadgets and wires . I found a VDO dealer who has a speedometer and clock repair shop. He will restore my original tach . It will cost about $200. I think it's is a good idea. He tested and it is definatley defective., My injectors are ready. I don't know if the mechanic plans to put them in or If I should. I don't have the special tools for pressing them in place. They didn't come out easy I pried them up with a flat bar. I hate doing things like that.

[JD-MDR]

Installed the rebuilt injectors Friday . The motor runs great. I ran it about 10 hours to Scorpion Bay and back at 2100 rpm's . I easily got 2700 RPM'S and it wasn't opened up. No Smoke . The rebuilt Tach works perfectly. I'm glad I had the old one fixed It looks new and if I got a different one I probably would've needed different wires or something. In an earlier post I asked about running without the thermostat. I got responses saying no problem. The mechanic told me that its not good to run the engine cold and it is best to use the thermostat to keep the motor at optimum temperature. One reason might be to warm the oil to flow better. anyway just a note. I got the money to finish my chain plates . I'm waiting to make sure I get more work (income) to survive. I'll post photos later of my chain plates as they are and when I get them out and then the new G-10 installed.