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Old 16 August 2017, 02:29   #1
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Country: UK - England
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Tiny Tach readings

Some time ago I installed a Tiny Tach on my little 15 hp 4 stroke mariner outboard. I only get a reading of 2950 revs at wide open throttle but I am managing about 21mph at these revs on my 3.4 m rib so I kind of think the engine is flat out.


I just checked the Throttle linkage and with the throttle lever pushed full forwards the throttle just hits the stop on the Carb


The Idel speed is 690 rpm

Does anyone else use this little tachs and if so what do I set them to on this engine

Thanks

Dennis
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Old 16 August 2017, 03:32   #2
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Been messing with the settings and I think I have sussed it:


Instruction Book for engine says Idel speed in gear 950 - 1000 rpm


I have set the Tech to 02 setting and I now get 1150 RPM at idel out of gear. Given that this will drop a bit in gear I think this is the correct setting.


Will test WOT when next on the water.


This only cost me £4.99 but it seems to be ok now


Dennis
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Old 16 August 2017, 03:38   #3
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Price Drop


Now only £4.55 with free postage


Spark Plugs Engine Digital Tach Hour Meter Tachometer Gauge Motorcycle ATV J2X4 | eBay


Dennis
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Old 16 August 2017, 04:08   #4
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dennis i bought a cheap one and it was crap i then bought one same as fenlander £20 check his threads out for the make or supplier.

just looked on the suzuki test reports for a suzumar 3.56m weight inc engine 93kg 15 hp suzuki 4 stroke engine fuel carried 8ltrs, crew weight 75kg equipment 40 kg

4000 rpm 8 knts
5000 rpm 13 knts
6000 rpm 17 knts
6200 rpm 18 knts

2.31 ltrs / mile PROP SIZE 9 1/4 X 9
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Old 18 August 2017, 03:08   #5
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Quote:
Originally Posted by jeffstevens763@g View Post
dennis i bought a cheap one and it was crap i then bought one same as fenlander £20 check his threads out for the make or supplier.

just looked on the suzuki test reports for a suzumar 3.56m weight inc engine 93kg 15 hp suzuki 4 stroke engine fuel carried 8ltrs, crew weight 75kg equipment 40 kg

4000 rpm 8 knts
5000 rpm 13 knts
6000 rpm 17 knts
6200 rpm 18 knts

2.31 ltrs / mile PROP SIZE 9 1/4 X 9
Mine seems ok now it is set up right. It was consistent and solid it just was set to a 2 stroke setting not a 4 stroke

I think that accuracy to within 50 rpm is fine as long as it is consistent so you get a feel for you engine

Dennis
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Old 25 August 2017, 02:52   #6
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Did a real world test on Wednesday

WOT 5700 RPM on my 3.4 m RIB with my mariner 15 hp 4 stroke 20 Knts with approx. 2 knt tide going with the tide.

It sounds as if the engine could do more but that is most likely cos I am sort of used to the sound of 2 strokes I think

Dennis
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Old 25 August 2017, 03:22   #7
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what prop are you running and what is max revs of the engine dennis out of interest
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Old 25 August 2017, 03:43   #8
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Quote:
Originally Posted by jeffstevens763@g View Post
what prop are you running and what is max revs of the engine dennis out of interest
It is the prop that was with the engine and I cant seem to see the markings on it which I tend to find with most of my props. The Max on the Tach is 5700 and the book says 5000 - 6000 rpm so I think all is ok


Dennis
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Old 25 August 2017, 05:16   #9
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Quote:
Originally Posted by Bigplumbs View Post
It is the prop that was with the engine and I cant seem to see the markings on it which I tend to find with most of my props. The Max on the Tach is 5700 and the book says 5000 - 6000 rpm so I think all is ok


Dennis
i would say you're spot on not a million miles away from the suzuki figures, you might get a bit more out of it coming down a pitch but you could hit the rev limiter if you did
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Old 28 August 2017, 08:17   #10
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I have this tiny tach on my 20hp 2stroke Merc, works perfectly.

Readings that I got are:



2 = 2 persons on board, 4 = ..
Boat is a Mercury Ocean Runner 340 RIB, prop is BlackMax 10 3/8 x 13P.

This year I have raised the engine approx. 3cm and maxed out at 6200RPM and 28kts (GPS). With 44 liters I did exactly 100 NM, average speed of 17kts.
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