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Tachometer installation method found!

Aug 25, 2015
28
San Juan 28 Sequim, WA
I found installing a new tach to be quite challenging with not enough info on line to make it simple for me so I want to share my weeks of experience to help the next guy wanting to do the same. My engine happens to be a Yanmar 2QM15 but I think this instruction will work for most diesel inboards. The RPM output can be found from the alternator if there is an electrical connector on it which sends a signal (my alternator needed an "R" which it didn't have so I needed a sensor which is no longer made by Yanmar. I think other alternators may be labeled "AC" for that connection. It's also possible to have an alternator shop install the tach output on the alternator but I found that to be expensive so I chose the sensor which was the original installation method. I found a diesel tach with an hour meter as well as the tach sensor on Amazon manufactured by a Chinese company called KUS and distributed by Springautoparts (see links below). If your boat never had a tach you'll need to pull the tach plug from the engine which will be above the flywheel where it senses the engine's rotation and order a sensor to match the plug. I went to ACE hardware and matched up my size and thread there. Springautoparts has a variety of sensors to match your plug size. Mine was an 18mm fine thread and it fit perfectly. I just screwed it in until it touched the fly then backed it off a quarter turn.
Maybe you can order these together and save shipping by contacting Springsautoparts directly. The shipping is pricey but fast....two days to us near Seattle.
https://www.amazon.com/gp/product/B01DKCDCZO/ref=od_aui_detailpages00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B01DP6FJ6K/ref=od_aui_detailpages00?ie=UTF8&psc=1
 
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Likes: tfox2069
Nov 25, 2015
45
Endeavour 32 Middle River, Md
Pretty cool..Thanks for sharing your info and upgrade.
I would love to add a tach to my tach-less 2QM20 but don't know how to locate the "tach plug" you spoke about...do you have any pics?
 

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Aug 25, 2015
28
San Juan 28 Sequim, WA
My plug looks like what you'd see to drain your oil on a car and is found above the flywheel which will be at the back of your engine. Mine is on the port side near the top. I even had wires by the plug which went to the instrument panel since the tach was an option. I used one to power the sensor and another to send the signal to the tach.
 
Feb 6, 1998
11,321
Canadian Sailcraft 36T Casco Bay, ME
I found installing a new tach to be quite challenging with not enough info on line to make it simple for me so I want to share my weeks of experience to help the next guy wanting to do the same. My engine happens to be a Yanmar 2QM15 but I think this instruction will work for most diesel inboards. The RPM output can be found from the alternator if there is an electrical connector on it which sends a signal (my alternator needed an "R" which it didn't have so I needed a sensor which is no longer made by Yanmar.
The old tach sensor part number for the 2QM15 was 124070-91160 it has been superseded by part # 128170-91160 which is still readily available. Course like all Yanmar stuff it is not inexpensive..

Adding a stator tap to an alt should be about $25.00 - $40.00 it's simply one wire soldered to any one of the three stator coils.
 
Sep 15, 2009
6,241
S2 9.2a Fairhope Al
you can get a tach proximity sensor from napa for about 25 bucks and it comes in metric threads
 
Sep 15, 2009
6,241
S2 9.2a Fairhope Al
"tach proximity sensor"...are these accurate?....how to install?
they are as good as it gets ...but looking at your pic i don't see a plug in your bell housing ...its the same thing that yanmar sells for there tach equipped engines what engine do you have
 
Sep 15, 2009
6,241
S2 9.2a Fairhope Al
Tolivar......one more thing do you have gate valves on those through hulls if so you need to consider changing to ball valves.... that is sort of a bad thing as in could cause you to sink your boat
 
Nov 25, 2015
45
Endeavour 32 Middle River, Md
2qm20...you have a good eye woodster and ok you also have my attention, how can my gate valves (I have already replaced some)
" cause me to sink my boat" ?
 
Sep 15, 2009
6,241
S2 9.2a Fairhope Al
they will get clogged and you may not be able to close them when you need them the most ...i don't know where you got them but if they are red brass like form hd or lowes they will rot in short time in salt water
 
Sep 15, 2009
6,241
S2 9.2a Fairhope Al
also from looking at your gearbox the shifter is on the opposite side from mine and all others i have seen ...what kind of gear box do you have...
 
Nov 25, 2015
45
Endeavour 32 Middle River, Md
gate valves are original and work well
Tinytack looks like a viable option, what do you connect a Tinytach to?
 
Jun 12, 2016
10
Hunter 28.5 Pensacola
....and if you have a Tach that has quit working or is intermitant, remove the cable(which is not easy on a 1987 Yanmar and being removed for the first time) and soak it in a baking soda solution with vinegar. Screw it back in and it will work great.
 
Nov 22, 2011
876
Ericson 26-2 San Pedro, CA
as a sailor once said....."Your boat your choice"....
Gate valves work just great--until they don't.
That's true for everything subject to failure. But with gate valves the big problem is that it is often not obvious when they have failed. They may appear to be closed nice and snug when they really are not. That's why they have no place on anything mission critical like keeping your boat afloat.
 
Mar 2, 2008
406
Cal 25 mk II T-Bird Marina, West Vancouver
R
gate valves are original and work well
Tinytack looks like a viable option, what do you connect a Tinytach to?
Read the instructions on their site. The diesel model has a simple sensor you clamp onto one of the high pressure injector pipes. Measure your pipe diameter in mm to order the correct sensor. Calibration is just entering the number of cylinders. You can surface mount the display with double sided tape or small screws. Mine has been working for over 9 years with no problems. The run time hour meters are only good as service reminders that can be used similar to a trip odometer in a car.
 
Jul 7, 2015
22
Hunter 33_77-83 Kemah
....and if you have a Tach that has quit working or is intermitant, remove the cable(which is not easy on a 1987 Yanmar and being removed for the first time) and soak it in a baking soda solution with vinegar. Screw it back in and it will work great.
Do you take the entire cable off and soak it, or just where it attaches at the engine? And where does it attach at the engine? And thanks for the comment, my tach has just started reading erratically.
 
Jun 12, 2016
10
Hunter 28.5 Pensacola
It's located on the flywheel on the left top side of the engine as you are looking at the engine facing toward the front of the boat where the other guys are describing it. I have the 2 cylinder Yanmar and the picture above is a little different than my engine(and a lot cleaner).You can disconnect the cable at the plug and wire brush it and soak it's connector also if it is corroded. I'd probably do that first and then if it doesn't work, take the sensing plug out. It is a large MM plug and I had to use a socket and then a long(18') arm on the end of my socket wrench to break the seal loose. Once it moved, I could screw it out with my fingers.