VDO Tach / Aetna Sender / Mag-Pickup Combo?

[Harry Karaoglanian]

Hey Everyone!!!

Purchased a 38 Pursuit – 2002 with a pair of 6CTA8.3 450 Diamonds (CPL 8089/2172?) back in Oct 2020. ESN – 46157332 / 46156149

I phototached the viscous damper for each engine and compared to the current VDO Tachs and I am geting +/-5% at each 100 RPM. Checked from 650 all the way to 2950. Almost a 5% variance each 100 RPM. The VDO tach is showing lower than actual. I have found a website with what appears to be my tach and the dipswitch setting based on flywheel tooth count. The VDO tach has part# 333-229B, which I can’t even find on their website but I think it is the “VANGUARD” series from 1998. I think I found a manual.

Further, I have noted that (unsure if previous owner or mfgr???) installed an AETNA 8901 sender at the front of both engines… then I checked for a mag-pickup at the flywheel, and sure enough that is there as well. I have yet to dive deep into the spiderweb of wires going from the engine room to the dash to see which one is actually hooked up – so I have a couple questions:

Is this normal? To have a Aetna 8901 sender in the front of the engine AND a mag-pickup?

If the previous owners were planning an install of aetna tachs, then all I would need is the actual gauge to convert to Aetna tachs – then wire it up?

If it is just the mag-pickup and the Aetna 8901 is not being used, is the flywheel tooth count for my engines 127?

Therefore based on the the VDO Manual (attached) the dipswitchs should be X-X-O-O-O-X-O-X with X being on(up) and O being off(down). Right now the dipswitches are O-O-O-X-O-X-X-O, which looking at the manual it doesn’t even show as an option lol.

Attached are photos of the VDO Tach and the Aetna sender. I didn’t take a picture of the mag-pickup, it looks exactly like any of the photos on this site and is located behind the aftercooler on the flywheel.

Last question – the heads on these engines are chrome – do you think they are replaced?

Thank you so much in advance!!!

Topic

[Harry Karaoglanian]

Follow up

So I went down to the boat yesterday- unplugged the tach sensor on the flywheel (just from the wire, didn’t actually remove the sensor/mag pickup) and ran the engine. Sure enough- the rpms still worked. So this makes me believe there is an Aetna sender, attached to a VDO gauge. Is this normal? I’m assuming this definitely won’t work properly as there’s no dipswitch configuration for 8 pulses / revolution for the VDO gauges.

Do I just put aetna digital tachs and call it a day?

[Harry Karaoglanian]

Haha!!

LOL! That makes sense, the old owner had passed away a year before we purchased and he was a water ski boat racing champ. Loved engines and such. They appeared to have been maintained meticulously – but as far as how they ran her because the owner was a racer, unsure. Makes me woozy just thinking about it.

Thank you on the teeth count!!! As far as the tachs and two senders, I guess I’ll unplug the aetna sender and see if it changes anything.

Thank you again guys

[Rob Schepis]

Rocker covers were likely just to satisfy someone’s need for Bling.

Yes on the link, it was to show tooth counts.

[Harry Karaoglanian]

Rob

Hey Rob! Thank you so much.

Any idea on why they would have changed those rocker covers? I have no maintenance history on the engines.

The link you provided – it is for BEEDE, not VDO. Correct? I see the flywheel teeth count is 127. Thank you for verifying that!

[Rob Schepis]

Chrome rocker covers – not original.
Have you seen this: https://www.sbmar.com/articles/beede-tach-settings-cummins-flywheel-tooth-count/

[Harry Karaoglanian]

Pics

I kept trying to add pics by editing the post but it says that I was being blocked. Trying on this post

[Author]

Replies