# 25hp tiller tach



## Johnsk (Sep 20, 2019)

I have a 2017 mercury 25hp efi tiller Elect start power tilt and trim. I called mercury tech support and they told me there is no way to install a tach on my motor other than tiny tach which I have but have my doubts about its accuracy. Looking around at tachs you need a signal wire , ground , and power from ignition switch. Could I run a wire from battery that is switched run a ground and wire to signal ? My ? Is where would I get signal from? Has anyone done this ? Thanks everyone


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## MrGiggles (Sep 20, 2019)

The signal is usually taken from one of the stator legs.


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## Johnsk (Sep 20, 2019)

Yes thank you has anyone done this and why would mercury say can’t install tach


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## Sinkingfast (Sep 20, 2019)

The tiny tach counts impulses...unless set up wrong it will be accurate..probably dead on..


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## Johnsk (Sep 20, 2019)

It reads a little high at idle and wot I’m just under 5400 guess I need to look at props. 2018 tracker grizzly 1648 2017 merc 25hp bought new as left over middle of 2018 runs well maybe 35 hrs mainly using trolling motor to bass fish. 9.5x11 3blade when I do prop wizard that’s prop it recommends says I should hit 5600 rpm getting 5400 and 24mph . 2 guys 2 batteries trolling motor so not over loaded.


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## turbotodd (Sep 21, 2019)

The tiny tach is about accurate as you're going to get. 

Those inexpensive analog round gauges? I've never seen one that was totally accurate-there are more ways for INaccuracy due to the movement, voltage input, grounds, etc. That and they're a little more involved as far as installation.

I've personally tested a few TinyTach's and they're all within 5 or 10 RPM depending on the model. Some will read down to 5 rpm, some only down to 10. I've tested them against the EFI's actual logged RPM and they're spot on with what's actually reported to the ECU. Never had one that was inaccurate. I've had one with a dead internal battery but that was the ONLY problem.


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## GYPSY400 (Sep 21, 2019)

Tiny tach is the way to go.. pretty cheap on the eBay too!
Just remember to set it up properly for a 4 stroke

Sent from my SM-G903W using Tapatalk


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## Johnsk (Sep 21, 2019)

Thanks everyone for response I have one on motor wot 5300-5400 thought might be low because 6000max I guess with my load if I want increases rpm and top speed I will need to Change prop a lot of prop tools are saying to go to 4 blade rpm 5750 and 28mph currently running 9.5x11


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## GYPSY400 (Sep 21, 2019)

Given that your running 5400 loaded.. you would probably run 5750 at 28mph empty. If you pitch down to 10" to gain rpm, the speed will stay about the same. A 4 blade will get you out of the hole better, but you will sacrifice top speed.


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## Johnsk (Sep 21, 2019)

yeah guess I’m just bored all projects done on boat lol. Bring gps tomorrow fishing see how it runs


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## Johnsk (Sep 23, 2019)

Was out Sunday tiny tach would hit 5400 WOT but took some time and trimming of motor gps read 23 mph with normal fishing gear 2 guys trolling motor 2 batteries. That seem about right tracker grizzly 1648 with mercury 25hp efi ?


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## wmk0002 (Sep 23, 2019)

I have been wondering this as well. I've always used the Hardline inductive tachs, but for some reason my readings are erratic on this old Yamaha 30 I recently got. The motor has a wiring harness ran to a key switch in a junction box so I should have the wires needed to set up an analog tach. I just haven't had any luck finding anything advertised as a marine tach that is not 3" or bigger in diameter. I'd prefer a small 1.5-2" one I could mount near my depth finder.


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## Johnsk (Nov 8, 2019)

I put a 4 blade spitfire prop on tpm went up to 5700/5800 on the 25hp efi speed stayed same 22-23 mph hole shot was much better was a little harder to steer. Could take running 19mph cruise so I sold motor yesterday , lucked out guy got rear ended and Insurence gave him check for his outboard so I sold mine in a week, and didn’t lose much$. I’m picking up a 2019 mercury hp weds, question is with a 2017 mercury 25efi was getting WOT 22-23 what type of speed should I expect with new mercury 40hp it’s a 2018 tracker grizzly 1648?


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## jasper60103 (Nov 8, 2019)

Johnsk said:


> I put a 4 blade spitfire prop on tpm went up to 5700/5800 on the 25hp efi speed stayed same 22-23 mph hole shot was much better was a little harder to steer. Could take running 19mph cruise so I sold motor yesterday , lucked out guy got rear ended and Insurence gave him check for his outboard so I sold mine in a week, and didn’t lose much$. I’m picking up a 2019 mercury hp weds, question is with a 2017 mercury 25efi was getting WOT 22-23 what type of speed should I expect with new mercury 40hp it’s a 2018 tracker grizzly 1648?



Can you post pics of your grizzly? I have one and just curious about your setup.


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## turbotodd (Nov 8, 2019)

Johnsk said:


> I put a 4 blade spitfire prop on tpm went up to 5700/5800 on the 25hp efi speed stayed same 22-23 mph hole shot was much better was a little harder to steer. Could take running 19mph cruise so I sold motor yesterday , lucked out guy got rear ended and Insurence gave him check for his outboard so I sold mine in a week, and didn’t lose much$. I’m picking up a 2019 mercury hp weds, question is with a 2017 mercury 25efi was getting WOT 22-23 what type of speed should I expect with new mercury 40hp it’s a 2018 tracker grizzly 1648?



Real low 30's most likely. If it has PT&T maybe up closer to 35.


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## Johnsk (Nov 9, 2019)

If someone could tell me how to post pics I will


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## Johnsk (Nov 9, 2019)

Thanks for replies it does have pt/t installing weds will let u know speed


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## Johnsk (Nov 9, 2019)




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## Johnsk (Nov 9, 2019)




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## jasper60103 (Nov 9, 2019)

Nice clean setup. Thanks for sharing. 

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