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I have a thread open with alarm issues. I figured would open a new thread for seperate issue. My 1999 Yamaha c115 I am trying to size the prop. The prop that was on it when I bought it was so corroded I can;t see any writing (the previous owner does not remember he just said th eboat goes about 40 MPH with 2 people)) I started wit a 19 pitch because that is where the internet seemed to take me. When I got on the water. My RPM went right to 6000 - 6300. (Speed at 29 MPH) We are not sure my RPM is right though. At IDLE my rpms show 1200 RPM but it does not sound that fast. My gauge is set for 6C but I am not sure that is right either. I did buy a cheap 21 pitch however, the engine could hardly get on plane and maxed out at 5500 (the true max WOT) and speed was no different than 19 pitch and the engine sounded like it was too slow.. So the 21 pitch is too big.. How do I check the true rpms of my engine or if my tachometer is set up correctly? I am reading the WOT is 5000 RPM (4500 - 5500)
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Normal idle should be in the 750 to 850 RPM range…. -
In gear most motors like 750.Comment
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I would look at the manual for that Tach to see what it says on how to set it.Originally posted by Brfyan1965 View Post
hook up a known good tach to see what it readsComment
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Folks don't like to say what brand and model of stuff they use. Top Secret Info I guess.Originally posted by 99yam40 View PostComment
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What Teleflex says.
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System won't let me update my own post. Strange that.
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P = Poles? Nope. Or maybe.
Yamaha uses the term poles with respect to tachometer settings. Settings of 4 poles, 6 poles or 12 poles.
Two poles per magnet. N & S. One pass of a two pole magnet equals one pulse. 6 magnets having 12 poles equals 6 pulses.
Others use pulse settings for their tachometers. See below. Confusing? I think so.
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First time I am seeing something like this. WTH?
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to be honest I do not know what brand. I assume all brands are the same, since they all use the same numbers. (The ones i looked up) I believe it has something to do with how many poles the alternator has. Or how many pulses the alternator pulses per rotation so if you have a 6 pole alternator the tack would be set at 6C if you have a 12 pole. It should be 6P (So I am told when I ;ok it up)
I am not sure how to tell how many poles the engine has, hence why I asked.
My current tach is set at 6P. I am questioning if this is right or not. As My Idle RPM is running at 1200 RPM according to the tach Yet it sounds a lot slower than this. (It sounds like the idle of any outboard I have ever had) taking this and the issue I saw with the props (19 pitch runs at 6000 RPM. Yet when I go to the next pitch (21) it is to much for the engine. Yet brings the tach RPMS down to max normal range WOT) That and engine speed actual vs what i was told. Makes me wonder if I have a tach issue as if it is not set up right..
even if I bought A new tach, I would not know how to set it up.
Anyone if anyone can help me out please do..
if n one is sure. I will try to figure it out somehow. I do not want to buy a new tach when i do not know if this really wrks or not (i already spend 200 on a prop I can not use based on the RPM I was reading on said tach)
I do have another tach on a Mercury 40 HP 4 stroke on the pontoon I bought this boat to replace. This is my first yamaha outboard. I am not sure if the two teaches are comparable. If it is, I can try that, But I still do not now how to set it up correctly for this particular engine. And there is nothing in the Seloc manual that I ave tat sows itLast edited by Brfyan1965; 05-23-2022, 07:56 PM.Comment
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find out what tach you have and then find a manual for it
how are we supposed to know what you have?Comment
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If you dont trust your tach then buy a cheap portable tach on Amazon for $30 and put it on the engine...that will tell the story.Comment
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