Need tach for 75 hp

[eddy622611]

Hi,

I have a 20' Crest pontoon with a 1975 75hp Chrysler. I'm very pleased with the way this motor runs. I have two props. The one that was on the boat when I bought it is a 13x15, it will run the boat 18 to 20 mph WOT. I can pull my kids on a 6' diameter tube with no problem and the fuel consumption isn't all that bad - about 10 to 15 gallons a day.

Last night I thought that I would try the spare which is a 13x17, at low throttle it ran smooth and a little faster at the same setting, but at WOT the motor sounded different with boat only reaching 17 mph on the gps.

So I would like to hook up tach and compare the two, also I feel it would be convinent for general usage. Which leads to all my questions:

1.Can you buy one new or would you have to find one second hand
2.How much can I expect to pay
3.Can someone explain what is 20 pole, and is that what I need
4.Can you supply me with a wiring diagram

Thank you very much. I have already learned a lot from reading the previous posts. This is a great group.

Brian M. Olsen
Youngsville, PA
Kinzua Dam

 

[Frank Acampora]

Re: Need tach for 75 hp

You need a 12 pole tach. 20 pole is for newer chrysler and Force engines with the one piece lower unit and 20 pole alternators.

I would shop around and buy a new one. I boats sells them, Teleflex sells them and there is a Tiny Tach that is cheaper and seems by consensus to work well.

I would not buy used electronics because they ALWAYS "worked when shipped." The extra cost for a new one is in my opinion, well worth it in this case unless you absolutely trust the seller.

Wiring is quite simple and self explanatory with the instructions packed with a new tach. However: Power comes from the "I" terminal of the ignition switch, Ground goes to any ground wire, and Signal is from the WHITE wire off the CD box on the engine terminal board. This white wire runs through the cable up to the ignition switch but is not connected and unused on your engine unless you have a tach installed. Since your 75 is a three cylinder engine, you set the switch on the back of the Teleflex to "3"

Other tachs may have a setting of "3" for 12 pole alternator and "4" for 20 pole. If the tach you buy is like this, then take signal from the purple wire which is also unused on your engine, and again, set the switch to "3". Not sure about wiring Tiny Tach but I suspect it is also simple--maybe someone else will jump in.

By the way: Props for that engine are getting difficult to find. If you ever need one, try over at The Chrysler Crew.

Where is Youngsville in relation to Philly?

 

[eddy622611]

Re: Need tach for 75 hp

Frank,
Youngsville is in N.W. PA about 40 miles east of Erie. I have lived here for the last 18 years, but I was raised in Gilbertsville, PA. We did alot of boating at Black Rock and Blue Marsh. Your advice to buy new over used makes alot of sense. I bought a water pump kit and some seals from Franz Marine at the Chrysler Crew. Very pleasant experience.
Between the two sites I learned everthing that I needed to fix the few small problems that I have had with this motor. Good thing too, because nobody around here will work on an old Chrysler. Thanks, Brian