Ques. If a tiny tach is reading correctly at idle can one assume it is reading correctly at wot? Do I trust the tach? "Earballing it" it does not sound revved out but this my 1st 4str. the facts below: riverhawk b60 merc 20hp 4 str. prop. 10p 3500 rpm @ wot top speed 25mph (gps) ANY food for thought is appreciated
Mercury 20 FourStroke Specifications HP @ Prop 20 kW @ Prop 14.9 Max RPM (WOT) 5400-6100 Cylinders 2 (in-line) Displacement (CID/cc) 21.4/351 Bore & Stroke (in) 2.40 x 2.36 Bore & Stroke (mm) 61 x 60 Cooling System Water-cooled w/thermostat Ignition System CDI w/ electric spark advance Starting Manual or electric Gear Ratio 2.15:1 Gear Shift F-N-R (Shift-in-Handle Tiller or Remote Control) Steering Tiller or remote Alternator Amp 12 Volt / 11 Amp Alternator Watt 139 Trim Positions 6 or power tilt Shallow Water Drive Standard Exhaust System Through prop Lubrication System Wet sump Recommended Oil Mercury 4-Stroke Outboard Oil Oil Capacity 1.0 L / 1.1 Qt. Fuel Induction System 2-valve single overhead cam Remote Fuel Tank Standard Remote Fuel Tank (US Gal) 6.6 Remote Fuel Tank (L) 25 Shaft Length (inches) 15/20 Shaft Length (mm) 381/508 Dry Weight (lbs.) 115 Dry Weight (kg.) 52 Operator Warning System Low oil pressure / Over--rev Available Propellers Standard equipment CARB Star Rating 3 Sounds like you're getting the right speed but the wrong rpm's based on the engine specs. Which model tach did you get? Appears to be reading half of the true rpms. A tach designed for a 1 cylinder engine and being used on a 2 cylinder engine might read only half the rpms.
the fac. sent a tt226r-2x w/ an L written next to the model number for the motor .I did it over the phone to eliminate mistakes. I did a total of 4 wraps plus 1/2 wrap at each end and trimmed Talked to the fac. and was advised I might need to put another wrap on it because of interference--just a "wittle" late to do now!!!!!!!! :
Splice another chunk on, its an induction coil. The short length of the wire added shouldn't affect the electrical signal produced.
the instrc. say no-----but i like the idea and will do so thanks I thought I might go to a 9 pitch---good idea ofr bad?
Get your tach working right first. If you are in the power band 5400-6100 rpm then no need to change.
I just got mine yesterday from the factory. I ordered the TT226R-2C because that's what I thought I needed from reading the descriptions on their site. I received the same model as yours, the TT226R-2X with the hand-written "L" next to it, with a note on the packing slip that it was sent because it was the right one for my motor. I have a Johnson 15 2-stroke. I described my motor when I ordered it. I don't know what the difference is, but assume the factory knows best. Going to install it this weekend and try it out. Glad I saw this post, so I won't be trimming anything off until after I test it. I'll let you know how it works. Kemo
sounds like i am the ginny pig [smiley=dancing-smilie.gif] [smiley=shucks.gif] adjustment was to be done one wrap at a time await the results with great anticipation ;D
I've never seen a Tiny Tach installation but if it is sensing spark plug firings then it shouldn't be the same part number for a 2 stroke and a 4 stoke - right? Tom W
Some engines fire the plug for the cylinder on every rotation of the flywheel. Others fire it on every other rotation, so half the number of rpm's would be read.
Sounds like the tach factory thinks his 4-stroke fires every time. I'd question the motor factory on what that particular 4-stroke does. Kemo
are we having fun yet? ok --- the tt is showing proper rpm at idle ---does that not blow out the firing theory??????????? does the fact that I am 1500-2000 ft up make a difference ;D : this is one awesome site wish I knew about it when i was still a flatllander thanks ken
at idle the engine is in the zone according to the manual and the tach''' so.................. lets keep the brain waves going-----that way if i have to call the fac. again i will have the collective i.q. behind me---meanwhile i need to get some wire and good weather for the test of previous fac. correction info and bretts splice idea KEMO----waiting to heart on ur install
In My Opinion I would go with an 11 Pitch But I am Basing that on my 15 Horse Yamaha I run a 10.5 or 11 but by X what I would have to check the prop box Dave At Least i can hear when the Yamaha hits the rev Limiter ... Then go up one Pitch LOL
FYI>>> emailed the fac. and was advised the unit sent is correct for multi-cyl. outboards ----the :L: stands for a light fliter put into the unit to mitigate interference-- hmmmm!
Sorry, didn't get a chance to do my TT yet. Sometimes I get a chance to do other stuff (for money) and I have to take advantage of it. Hope to get back to the boat tomorrow. Kemo
I wonder how you'd check your tach-uracy? :-? found it... http://www.cadvision.com/blanchas/54pontiac/tach.html
