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Old 25-06-2021, 19:50   #1
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Tach drive part Perkins 4.236

Hello All,
I am searching for an adaptor part for a mechanical tach drive on a Perkins 4.236. Part #38 referenced in the drawing below is the required part and was on pre-1986 (?) engines. The part is not available any longer and despite an exhaustive search and many phone calls, nobody has the part or have a clue where to find one. Anyone have a lead as to where to find the part or are there any suggestions where to find the dimensions of the part to have a machine shop fabricate? Bolts to the fuel pump gear.
Thanks!

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Old 26-06-2021, 16:01   #2
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Re: Tach drive part Perkins 4.236

That’s a tricky part to find but “Aetna engineering” supply tachometer parts ....and alternative fixes... for your engine. Click image for larger version

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Old 26-06-2021, 16:04   #3
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Re: Tach drive part Perkins 4.236

Oops..... that’s from Aetna, here’s where to find emClick image for larger version

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Old 26-06-2021, 18:28   #4
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Re: Tach drive part Perkins 4.236

Thanks, SkipperPete. I have the Aetna Engineering parts, which I have used before on a previous boat that had a Westerbeke 4-107. Great product; loved it, but unfortunately I will need the part requested in the original post in order for the Aetna product I want to use to work. Aetna is aware and are "looking into it". Without the part #38 in the diagram, the Aetna product is useless. I want an alternative to the tach running off the alternator. My hunt continues.
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Old 27-06-2021, 12:34   #5
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Re: Tach drive part Perkins 4.236

Perkins was a very commonly used engine in Ford Dexta and Massey Ferguson many of the larger 6 cylinder engines were used in various trucks in the US market also, most would have had mechanical tachs. Zillions used in the USA in the past 50 years.
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Old 27-06-2021, 14:12   #6
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Re: Tach drive part Perkins 4.236

Yup. And yet, still not able to find the part I need. A bit frustration.
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Old 27-06-2021, 15:26   #7
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Re: Tach drive part Perkins 4.236

Just throwing it out there, is this something that could be produced on a 3D printer?
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Old 27-06-2021, 16:26   #8
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Re: Tach drive part Perkins 4.236

Had a similar problem ages ago with an old Ford 590 E series engine. But the problem was the actual mechanical tacho itself. It was irreparable, so I removed the mechanical cable that was attached to the engine and installed an electric one running off the alternator with a VDO instrument. The only problem I had was with the calibration process.

You will probably also have an existing wiring loom from the alternator to your instrument panel so installing wiring from the alternator can utilise this loom. Tidier than a mechanical cable.
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Old 27-06-2021, 17:02   #9
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Re: Tach drive part Perkins 4.236

I have 700 amp hours of LFP with a substantial solar array so the alternator often does not have any output. So running off the alt is not desired. If I can determine the bolt pattern, I'll get a machinist to make the part. I was hoping someone here would be familiar with the part or have access to an old 4.236 that still had the part installed (pre-1984 models had the part I've been told). As pointed out, the alt is the source for tachs for most all, but the oldies.
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Old 27-06-2021, 18:49   #10
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Re: Tach drive part Perkins 4.236

I was wondering why you were reverting to the mechanical drive.
I guess that Aetna gave you all the other options. If “tiny tach” did a better panel display I’d recommend one of them.....they work off an injector pipe pulse.
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Old 27-06-2021, 19:19   #11
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Re: Tach drive part Perkins 4.236

Quote:
Originally Posted by gscriba View Post
Thanks, SkipperPete. I have the Aetna Engineering parts, which I have used before on a previous boat that had a Westerbeke 4-107. Great product; loved it, but unfortunately I will need the part requested in the original post in order for the Aetna product I want to use to work. Aetna is aware and are "looking into it". Without the part #38 in the diagram, the Aetna product is useless. I want an alternative to the tach running off the alternator. My hunt continues.
My solution is a "Tiny Tach". Do a search. It uses a sender bolted on to the High pressure fuel line to injector and counts the pulses. Works great and quite simple to install. I ordered the wrong size transduce nd had to return for the correct diameter fuel line on my 4-236. I think I ordered 1/4 inch and needed 6MM.
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Old 27-06-2021, 22:01   #12
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Re: Tach drive part Perkins 4.236

Quote:
Originally Posted by gscriba View Post
I have 700 amp hours of LFP with a substantial solar array so the alternator often does not have any output. So running off the alt is not desired. If I can determine the bolt pattern, I'll get a machinist to make the part. I was hoping someone here would be familiar with the part or have access to an old 4.236 that still had the part installed (pre-1984 models had the part I've been told). As pointed out, the alt is the source for tachs for most all, but the oldies.
i don't understand.. I'm still getting the RPM pulses to the tach even if the alt is not producing power. Same engine...
You're sure there is nothing else wrong with the tacho?
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Old 28-06-2021, 01:24   #13
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Re: Tach drive part Perkins 4.236

Quote:
Originally Posted by gscriba View Post
Yup. And yet, still not able to find the part I need. A bit frustration.
A left field suggestion - have you tried a farm tractor wreckers/graveyard?
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