Older Evinrude V4 Tachometer technical question

[John Bett]

Hello. I have a '69 Evinrude 85 with the spark amplifier points ignition that runs a tachometer off of the spark amplifier and (forgive me for not knowing the correct terminology)I call it a heavy tach, because at the boat parts dismantler, there are heavier tachs with a switch on the back for 4,6, or 8 cyllinders outboards and those are the ones that work for this application, and one I use now, but there are also the lighter tachometers which are for the I/O 4,6,and 8 motors with no switches and about 3 wires that dont work with this system. My question is, I also have a '72 125 with a pulse pack breakerless ignition system that the tach is supposed to run off of the alternator. Can I use the lighter style tach in this application as there are nicer tachs for the(as previously stated) I/O 4,6,and 8 cyl. motors. Thank you for your time!!

 

[John Bett]

Re: Older Evinrude V4 Tachometer technical question

Hello again. Sorry to ramble on, but I thought of 2 more related questions. First, if the lighter tach(as i spoke of above {bare with me on terminalogy, thanks})wont work, is there a circut I can build that will allow its use. Also, I notice that the alternator on my points type spark amplifier ignition system(69 85hp) looks identical to the one on my breakerless pulse pack ignition system(72 125hp).The points style system had spark amplifiers that had the tach circut and some that did not. so if the alternators are the same, and on the '72 125hp, you run the tach off of the alternator, couldnt you run a tach off of the alternator on the points system motor ('69 85hp) (Question being that why did they put a tach circut in the spark amplifier if you can run the tach off the alternator)? Thank you.

 

[Laddies]

Re: Older Evinrude V4 Tachometer technical question

Yes a alternator driven tach. will work on any system with a 12 pole alternator even a car alt. with a 12 pole stator

 

[John Bett]

Re: Older Evinrude V4 Tachometer technical question

Ok, I know my questions are confusing, but as I have gathered information, please let me revise my questions. The tachometers that I called the "light ones" are apparently for inboard conventional motors with distributors like in automobiles. Apparently they count the # of times that the spark plugs fire to give rpm. And the tachometers for the older OMC V4's (the ones I called the heavy ones because they are considerably heavier) operate from alternator impulses. My question is, Is there any way to use the automotive tachometers on the older OMC V4's (i.e. an electronic circut I could build)?<br />Thank You all..