# 25 2 stroke idle rpm range / tiny tach



## anytide

i set mine to idle @ lowest rpm and still run smooth in gear..


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## Guest

That's what you get they are indeed a POS. I have owned about a dozen and have never had one that read my RPM's correct. Super happy if it works just long enough for prop testing. I have also used a few other less expensive ones with the same results. 

Never owned a Sendek. I have been told a multimeter will display RPM's?


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## DuckNut

There's 100 posts on here where everyone buy one, tries to set them up to no avail. Then they call the company and send it back to get the right one.

I realy do not think they are reliable enough to trust for rpm. Nobody has ever complained that the hour meter doesn't work.

Agree with Brazil = POS


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## el9surf

I just need the rpm function to work long enough to get the right prop.


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## anytide

brand new motor?


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## el9surf

Yeah brand new got 6 hours on it.


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## el9surf

I guess worst case I have an expensive hour meter.


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## anytide

> I guess worst case I have an expensive hour meter.


yup
you could post :
load
hull
hp
rpm
someone might already know the best prop?


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## el9surf

Bob aka skinnydippin gave me some ideas on props but he has his motor higher up on a jack plate

Hull is a shadowcast
motor 25 hp 2 stroke mounted with cav plate in line with roof of tunnel.
weight - approx 500lbs with fuel, motor, battery, gear, not including anglers.
rpm's no clue


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## Dillusion

I have a tiny tach on my merc 15 2s, setting it to the 'correct' setting netted me double RPMs. I had to set it to the next setting down (180 I think?) to get it to work correctly.

Now it DOES infact read correctly, but only with the cowling off. WIth the cowling on, it traps in some interfearence and reads +-300rpm higher than it should.

Sucks but at least I can minus 300 from what I'm getting at WOT and know my RPMs lol

Bob did extensive testing with the 25hp on a SC, I would go with what he says. Even though he had a jack plate and a heavily cupped prop, you will need a similar setup.

There was a posting by Bob in the shadowcast thread somewhere that he states when mel used the stock prop it got the best performance, but the stock prop wasnt good when jacked up I believe.


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## DuckNut

If skinny gave you his info then use it. The fact that it is 1-2" higher won't make a noticible difference.

Let's say you do get the "correct" setting - how will you ever be able to know that it is giving the right reading? They just can't be trusted to be accurate - rather they are semi-reliable to give an approximation.


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## el9surf

Yeah I wasn't sure if the height was going to make a big difference or not.
I took it out tonight and played with the settings on the tach. After some trial and error I got it figured out. 
It idles in neutral at 2000 rpms. Once I put it in gear at the lowest throttle possible the rpms drop to 980-1000 and max out WOt at 5350 which seems about right. 
The manual says max rpm's 5000-6000

With an android gps app on my phone max speed topped out around 32mph. Right around 30 you can feel the boat starting to walk side to side tilll I engage the tabs and drop the bow a little.


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## DuckNut

2000 is half throttle - too high

Rev your truck to 2000 and slam it in gear - get the same result from your motor.

Something is not right


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## anytide

sorry if dumb ? - why you setting idle on new motor ?


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## Dillusion

My idle RPMs are like 750-800 (but my tinytach reads 900-1100 lol)


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## Creek Runner

All motors require an idle adjustment out of the box, if the dealer didn't do it shame on them.

2000 is way to high you're going to need a LU if you don't fix it.

Idle out of water in neutral should be about 900rpm
In the water with back pressure should be about 800rpm, and in gear it should be between 650-800 depending were your stall point is.


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## DuckNut

> Now it DOES infact read correctly





> My idle RPMs are like 750-800 (but my tinytach reads 900-1100 lol)


Which is it? Sounds like it still is not right.

I don't believe the Sea Pro is not out of the box. I think it is new to him but used for a season in Canada.

Save the aggrevation and send it back and use the proceeds to pay someone to get it right for you.


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## el9surf

Thanks for the feedback especially the rpm range from creek runner. I wish the owners manual would specify the whole RPM range rather than just the max rpm. I looked at both the merc and tohatsu manuals and coudln't find anything about the rpm's other than the max. Hopefully I caught this before there was any damage done. 

As much as everyone has mentioned the tiny tachs lack of accuracy it saved me a big headache. Having run a 4 stroke for the past 5 years I really had no sense of what normal was supposed to be going back to a 2 stroke. After the tach was hooked up and it read so high at idle I almost dismissed it as a complete misread on the tachs part. The only thing that had me thinking it could be right was the fact that it topped out on RPM's right where the manual said it should.


Long story short I took the boat out tonight and adjusted the idle screw. Someone at the factory didn't count their turns correctly during assembly. I had to back it out almost one full turn. I ended up just above the stall point where it didn't want to shake and sputter. Neutral is right around 950 in the water. In gear at the lowest throttle is 850.


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## anytide

awesome - if its smooth your good  the lower the rpm before stumble the better for the LU


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## el9surf

Duck Nut, just for reference the sea pro is sold brand new in the box with a 1 year warranty from Mercury. There wasn't even a hint of use on it. Everything was squeaky clean just off the assembly line. These are not the fish camp motors you are thinking of which are slightly used and also sold by smalloutboards.com


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## el9surf

Anytide the shift into gear is now like butter. Not quite so with the higer idle! I will change the lower unit fluid this week just to clean everything out. Manual says to do this at 10 hrs which I'm close to anyways.


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## anytide

awesome - idling at 2000 you'd need a clutch [smiley=1-whoops1.gif]
glad your set....


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## el9surf

Just glad I hooked up the tiny tach and noticed this before it became an issue. Also glad we have a forum with a lot of knowledge that we can easily reference. Thanks for all the feedback, it was really helpful. This is why I love microskiff


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## DuckNut

Glad to hear you got it figured out without any damage.

Thanks for the clarification as I did not realize a new Sea Pro could be had. Great find and you'll love it.


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## anytide

> Just glad I hooked up the tiny tach and noticed this  before it became an issue. Also glad we have a forum with a lot of knowledge that we can easily reference. Thanks for all the feedback, it was really helpful. This is why I love microskiff


yeah - theres a lot of fart smellers DN on here 
sorry -i meant smart fellers :-?


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## el9surf

?????


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## Creek Runner

Glad you got it worked out, and that I could be of help.

Just as a reference to one of your post above, the idle rpm has nothing to do with the WOT rpm, also weather a 2s or 4s the idle rpm range is about the same give or take a little but no engine idles higher than 900rpms when in the water with out damage occuring to the LU. 

Unless it's a race engine but you start those in gear!!!


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## el9surf

So the next obvious question. How do I know if i did any damage to the lu? It shifts smooth now and doesnt have anything noticably wrong. No wierd noises.... I ran it like that about 6 times total. Minimal shifting in those initial uses. Mostly just running to get the break in period out of the way.


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## anytide

the drain plug is usually magnetic , there will be metal flakes stuck to it if damaged.
-fine glittery specs are normal...


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## Creek Runner

> So the next obvious question. How do I know if i did any damage to the lu? It shifts smooth now and doesnt have anything noticably wrong. No wierd noises.... I ran it like that about 6 times total. Minimal shifting in those initial uses. Mostly just running to get the break in period out of the way.



You are more than likely fine, run it for the 10 hrs and then take it to the dealer for the 1st service just in case something happens you have that on your side if warranty claim is needed.

The drain plug is magnetic however since this is a new engine you're going to have metal fragmentation anyways due to break in. Again bite the bullet and let the dealer service it for the 1st time so you cover your A--. Even though I think your fine and have nothing to worry about.

Technically the dealer should have tested the engine out of the box, When I ran a dealership our policy was all engines were taken out of the box and tank tested all adjustment made that were necessary then we would drain the carb, clean the engine off and put it back into the box for pick up or shipping. no engine would leave my shop without this being done, I even had a guy by triple 250oxs Yamahas that were being shipped to Bermuda and we did this as well.


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## el9surf

Ok so I changed the oil this evening before reading your reply. All that came out was clear gear oil followed by some slightly dirtier oil with some glittery color and that was it. No visible flakes, so it looks like I'm good. I might change it again in another 10 hours just to make sure.


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## anytide

zoom zoom


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## Dillusion

> Now it DOES infact read correctly
> 
> 
> 
> 
> 
> 
> 
> My idle RPMs are like 750-800 (but my tinytach reads 900-1100 lol)
> 
> Click to expand...
> 
> Which is it?  Sounds like it still is not right.
> 
> I don't believe the Sea Pro is not out of the box.  I think it is new to him but used for a season in Canada.
> 
> Save the aggrevation and send it back and use the proceeds to pay someone to get it right for you.
Click to expand...

Why is it not right? I dont have a sea pro, I have a 2002 15 2s. I mentioned earlier my tinytach is ~300RPM's high with the cowling on....


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## DuckNut

Matty

If your rpms are at 750 and your tach reads 1000 then it does not infact read correctly and if you have to subtract 300 to get the idle speed then something is not right. 

What rpm's are you actually spinning if the tach shows 2500?

How do you know if it is idling at 750 unless you took it to the shop and had it tested or did it just read 750 and when you put the cover on it reads 1000 and you assume it is reading right? If it reads "correctly" at WOT how do you know? If it is off by 300 at idle and 0 at WOT then are you simply assuming that it is off by 150 at half throttle?


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## Dillusion

It reads correctly with the cowling off, and 300RPM high with the cowling on due to EMI somehow.

I tested this theory by idling and running at WOT with the cowling on and off.


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## Creek Runner

Just an FYI guy's any good mutlimeter will read rpm's and also some timming lights will also read rpm's. You can simply rent one from Napa get your readings make adjusments and return it.


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## Dillusion

> Just an FYI guy's any good mutlimeter will read rpm's and also some timming lights will also read rpm's. You can simply rent one from Napa get your readings make adjusments and return it.


Can you fill us in on how to read RPMs with a MM? I have one at home, and did not know I could do this.

What setting should the MM be on and where should I poke the red lead?


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## Brett

Shop Tachs


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## Creek Runner

> Just an FYI guy's any good mutlimeter will read rpm's and also some timming lights will also read rpm's. You can simply rent one from Napa get your readings make adjusments and return it.
> 
> 
> 
> Can you fill us in on how to read RPMs with a MM? I have one at home, and did not know I could do this.
> 
> What setting should the MM be on and where should I poke the red lead?
Click to expand...


Ha I'm not going to give you pointers on where to poke your lead, you're on your own on that one ;D

If your multimeter has a Tach function it will have an RPM setting and it requires and special lead that you will hook around the number 1 cylinder.


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## FlyWrecker

> ...
> 
> Long story short I took the boat out tonight and adjusted the idle screw. Someone at the factory didn't count their turns correctly during assembly. I had to back it out almost one full turn. I ended up just above the stall point where it didn't want to shake and sputter. Neutral is right around 950 in the water. In gear at the lowest throttle is 850.


I just received the same motor yesterday, I wish I read this thread in advance...The first thing I noticed was that my Tiny Tach was reading 2000 at idle with rabbit ears. I adjusted the throttle screw to just above the stall point. The tach now reads 1200 at idle with rabbit ears.  I have to believe it is reads couple hundred RPM's high. What was your final setting on the tach?


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## Dillusion

Which screw is the idle screw on a merc?  

OH, the air idle adjustment screw above the intake on the carb?

EDIT: No, thats not it! The one with the spring. I would the manual.

Yeah I had to adjust mine too, 1.5 turns out from all the way 'gently in'.


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## anytide

> Which screw is the idle screw on a merc?
> 
> OH, the air idle adjustment screw above the intake on the carb?
> 
> EDIT: No, thats not it! The one with the spring. I would the manual.
> 
> Yeah I had to adjust mine too, 1.5 turns out from all the way 'gently in'.


you dont sound sure..... :


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## HaMm3r

So, I haven't said anything up to this point cause the Tiny Tachs are well regarded, but I bought one of the cheap knock-offs on ebay for about $5 and it works perfectly on my Merc 25hp 2-stroke, and it reads very consistently compared to the other Teleflex analog tachometer I have onboard. Just thinking you might want to try one...


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## Dillusion

Well I just re-adjusted my carb screw to 1.5 turns out, and my idle adjustment screw to 'just barely touching and then 1/2 turn more' and the tinytach is still reading 650-750RPM at idle with the cowling off, so I think im good.


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## el9surf

My tiny tach is set at 180deg with the red wire wrapped around the bottom plug wire once, then around the top wire 2times and doubled back over the gap. 

I'm 950 rpm's in neutral in the water and it drops to 850 in gear at lowest throttle. The 850 seems a tad low like it's about to sputter once it goes into gear but it's significantly better than it was.


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## Dillusion

> My tiny tach is set at 180deg with the red wire wrapped around the bottom plug wire once, then around the top wire 2times and doubled back over the gap.
> 
> I'm 950 rpm's in neutral in the water and it drops to 850 in gear at lowest throttle. The 850 seems a tad low like it's about to sputter once it goes into gear but it's significantly better than it was.


Mine is set to 180 as well instead of the recommended 360, but my red wire is wrapped 4 times around only one of the spark wires as the manual states.


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## el9surf

I set mine up based on the reccomendation from the tech guy at tiny tach. It seems like it works well enough so I'm going to leave it alone. 

I'm fairly certain if it's set to 180 it's designed to be wrapped around both plug cables. If it's set to 360 it goes around one cable.

They also told me to help minimize interference to cut the excess off the red wire once you get the correct rpm's.


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## anytide

surf man -
you can drop it off @ my house for a month or two and i'll get her dialed in for you...


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## FlyWrecker

> I set mine up based on the reccomendation from the tech guy at tiny tach. It seems like it works well enough so I'm going to leave it alone.
> 
> I'm fairly certain if it's set to 180 it's designed to be wrapped around both plug cables. If it's set to 360 it goes around one cable.
> 
> They also told me to help minimize interference to cut the excess off the red wire once you get the correct rpm's.


 based on your posts, this evening I set mine to 180 degrees, wrapped once around the bottom spark wire, then two twists over itself to hold on...this is the ticket. 

This evening was the first chance I had to run the motor on the water. I spent the first 10 minutes adjusting the throttle screw. In water, idle, out of gear it reads 1100 rpms. In gear it idles at 900 rpms...my full rpm range was 900-5300 with the stock prop. 

Now I'm no expert, but that seems pretty close to being dialed in for being straight out of the box. I'm not looking for 100% perfection, just a safe operating range.


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## Creek Runner

> I set mine up based on the reccomendation from the tech guy at tiny tach. It seems like it works well enough so I'm going to leave it alone.
> 
> I'm fairly certain if it's set to 180 it's designed to be wrapped around both plug cables. If it's set to 360 it goes around one cable.
> 
> They also told me to help minimize interference to cut the excess off the red wire once you get the correct rpm's.
> 
> 
> 
> based on your posts, this evening I set mine to 180 degrees, wrapped once around the bottom spark wire, then two twists over itself to hold on...this is the ticket.
> 
> This evening was the first chance I had to run the motor on the water. I spent the first 10 minutes adjusting the throttle screw. In water, idle, out of gear it reads 1100 rpms. In gear it idles at 900 rpms...my full rpm range was 900-5300 with the stock prop.
> 
> Now I'm no expert, but that seems pretty close to being dialed in for being straight out of the box. I'm not looking for 100% perfection, just a safe operating range.
Click to expand...

If that is your real RPM's it's still too high. It's not going to break as fast as when it was 2000RPM's but it's still going to break.

To give all of you an example of a motor that is adjusted correctly. My 15hp in neutral in the water Idles at 800rpms in gear it idles around 650-700rpm without stalling. 900RPM's in my previous post is that MAX RPM's you want to be shifting at.

Also If had that much trouble out of a tach I would give it to my dog to chew on.


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## DuckNut

> Also If had that much trouble out of a tach I would give it to my dog to chew on.


 [smiley=1-thumbsup1.gif]

Adjusting the throttle to a reading that you have no idea if it is even accurate is not a smart move.

If you are referring to your motor being right out of the box - why are you doing it and not the dealer?


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## anytide

> i set mine to idle @ lowest rpm and still run smooth in gear..


-still tinkering huh!
tiny tach/ schminy schmack.....wasting your time/$
if you just like to play with it - thats cool....
-the lowest rpm possible in gear @ idle will be your best bet


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## FlyWrecker

> I set mine up based on the reccomendation from the tech guy at tiny tach. It seems like it works well enough so I'm going to leave it alone.
> 
> I'm fairly certain if it's set to 180 it's designed to be wrapped around both plug cables. If it's set to 360 it goes around one cable.
> 
> They also told me to help minimize interference to cut the excess off the red wire once you get the correct rpm's.
> 
> 
> 
> based on your posts, this evening I set mine to 180 degrees, wrapped once around the bottom spark wire, then two twists over itself to hold on...this is the ticket.
> 
> This evening was the first chance I had to run the motor on the water. I spent the first 10 minutes adjusting the throttle screw. In water, idle, out of gear it reads 1100 rpms. In gear it idles at 900 rpms...my full rpm range was 900-5300 with the stock prop.
> 
> Now I'm no expert, but that seems pretty close to being dialed in for being straight out of the box. I'm not looking for 100% perfection, just a safe operating range.
> 
> Click to expand...
> 
> If that is your real RPM's it's still too high. It's not going to break as fast as when it was 2000RPM's but it's still going to break.
> 
> To give all of you an example of a motor that is adjusted correctly. My 15hp in neutral in the water Idles at 800rpms in gear it idles around 650-700rpm without stalling. 900RPM's in my previous post is that MAX RPM's you want to be shifting at.
> 
> Also If had that much trouble out of a tach I would give it to my dog to chew on.
Click to expand...


Thanks for your post, I will continue to work on getting to your recommended rpms.


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