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Honda BF50 Tach Help...Solve this mystery...

So I have a 3Cyl 4 Stroke honda BF50 (2004) on a 12 foot center console rib.
The engine is supposed to idle around >1k and redline somewhere around 6k rpm.

My tach won't go past 3000 RPM. I understand there may be a rev limiter at neutral but even out on the water at WOT it stops at 3000.

I've replaced with a brand new Tachometer from Honda and set it to the setting in the instructions of the Tach that specifically mentions the Honda BF50.

Now I have a stock prop from honda, the one that came with the motor. Believe it's a 13 pitch. Here is the kicker. I get about 40MPH on this RIB at WOT and there is no way it's only doing 3k RPM.

Anyone out there have a clue what's going on, Tach should be showing somewhere around 5500-5800RPM according to the calculation.

I've tried every setting on the tach as well and the only one that reaches the 5500ish RPM also says the boat is idling at 2k rpm, so that's not right.

Help!
 
What brand tach are you using? Faria? Teleflex? Other?

There may be a fix for your problem depending on the tach that you have.

Also, do you have a built in hour meter in the tach?

The 50's before 2005 and older had an unusual tach signal.

Mike
 
Hondadude. It would be amazing if you could solve this. Yea. It's a teleflex gauge. Honda branded. Honda part # 37253-ZW5-010ZB. And yes it does have an LCD hour meter. Looking forward to your response.
 
First of all...be sure that your charging system is working correctly. It should be putting out a good 14v. If you can measure the current with a clamp on dc amp meter on the battery cable lead, that will tell for sure...since the charging coil provides the pulses to the regulator rectifier. One or the other could be bad. I think yours current output should be around 6 amps. It should be marked on the side of your motor. It has changed over the years, so I am not really sure what it is.

If all that checks out then a fix for erratic tachometer for 50's from 2000 to 2002, has many times worked for me. It is a resistor assembly that you connect in the tach circuit. It supposively suppresses the tach signal so the tach can read it better.

The part number is 06383-ZV5-315. The thing is somewhere around $28 though.

The guys at Honda can not explain to me why this has worked on models after 2002. I normally use Faria gauges and it only works with a Faria gauge if it has an hour meter. The guys at Faria can not explain it that to me either. So I hope this works with the teleflex.

Again, this does not always work. I hate to suggest you invest $28 on an if come maybe.

How is that for a list of disclaimers? I should have been a lawyer.

Mike
 
Thanks for the continued support Honda dude. Forgive if I haven't done this right but I measured the voltage across the battery. The voltage with the engine off is 12.63 with the motor on it is 12.75. Are u saying it should be 14v with the motor on? And I'm not sure where to measure the 6 amps.
 
If the motor is idling, it puts out a very low charge. It puts out its maximum charge at full throttle. You may not get to 14v, but if the battery needs charging, the regulator should increase the voltage toward approx 14v.
So, advance the throttle and see if the voltage increases at least a volt or two.

Again...your motor either has a 6 amp charging system or 10 amp charging system.

You asked how to measure the current...

Not knowing how electrically acute you are or what kind of meter you have, I do not want to try to explain how to measure it unless you have a clamp on dc amp meter like the one on this site. http://www.sears.com/shc/s/p_10153_12605_03482369000P?prdNo=1&blockNo=1&blockType=G1 There are all kinds and all prices out there.

With this kind of meter, you just put the clamp around the battery wire going from the battery to the motor. It reads it without any connections.

If you have a standard volt/ohm meter, you would have to actually open up a lead going to the rectifier and insert the meter leads into the circuit. You first have to have a meter that can read current higher than what you are trying to measure. You have to find the right lead...if you do not or if you hook your meter up incorrectly, you can damage the meter. So, we will not go there unless you really know what you are doing.

I know...a lot of work, just to get the tach working...

Mike
 
OK, I'll try at full throttle and see what the the volts are at the battery.

I have a regular Multi meter with the two probes. I'm very familiar with how to ruin a multi meter ;)
I set it to 10A when I was trying to read it but I tried to read at the battery obviously that didn't read anything.

So let me ask you something else, and again, I hope you are actually enjoying this thread and it's not just a Pain in your a$$. So I was thinking maybe it's one of the three charging coils that may be bad. If that was the case, the engine would still run correct? I'm talking about the 3 charging coils under the flywheel. I believe there are two attached to each other and one has it's own leads? Do you think it's possible that one is bad and that's why I'm having this issue? Would the engine purr like it does if one of them was bad?

The part number for the resistor pack for the honda seems to alleviate jerky tachs. Mine isn't jerky it's very solid, just doesn't get up to the right range.

Thanks again for your help,
--john
 
First of all...you did what you should not do with a meter set to read amps. Hopefully, your meter has an internal fuse for the current setting (most do). You blew the fuse when you connected accross your battery with the meter in the current setting. That was a no no.

As I said in the last post, I will not try to tell you how to read current over the internet...too many chances for error and damage like that one.

As to the three coils under the flywheel. Since you have three, that means you have 10 amp charging system.

One coil is the exciter coil...which provides the electric for the motor to run. That is separate from the charging system. This voltage is generally above 100v ac.

The two other coils are connected in parallel and provide voltage for the charging system. This voltage is typically around 20v ac depending on speed of motor.

As a reminder, your tachometer should be set at the "3P" setting for that year and model. That is the setting for 2005 50's and earlier.

The reason I suggested checking the charge output first, is that if the output voltage is bad, then either the reg/rect is bad or the charge coils are bad. Unfortunately, if the voltage is good, it does not prove that the reg/rect. if putting out the correct tach signal.

If you wanted to pursue checking the charge coils...you can measure the resistance of the coils.
The resistance should be between .17 and .23 ohms between the two leads. Now for how to measure it.

The leads from the charge coils get connected on port side of the motor under the black plastic cover. That is where most of the components connect to each other. Look for the two gray wires at the very top. You will have to pull the bullet connectors apart. The female connectors are the ones I think go to the coils. You can follow the wires to under the flywheel to be sure.

The motor is off during this test.
Set your meter to the lowest setting of ohms and connect your leads together to set the meter to zero. You are about to measure a very low resistance and everything has to be set just right to get an accurate reading.
Now, take your probes and put them between the metal connector and the rubber cover. That should hold the leads in place without using your fingers. If you touch the contacts with your fingers, the resistance of your body can affect the reading. The resistance should be between .17 and .23 ohms.

Once you get that reading....you need to measure for any resistance between either of the coil leads and ground. Take one of the leads out of the connector and touch a good ground on the powerhead. This is supposed to be an open circuit. In other words, it should be like the leads are not connected to anything. If you have a resistance reading, then one of the coils or one of the leads has a short to ground. That is not good. Once you do it for one lead, do it for the other.

If all that tests good, then most likely the charge coils are ok.

That was a mighty long answer to your question.

Mike
 
Mike,
Not yet. I actually found a good deal on that 06383-ZV5-315 Resistor Assembly so I was going to try that first. It just arrived this morning. I'm going to try to figure out how to install it and get it to work. I really hopes this solves the problem.
Here are pictures of the resistor and the instructions for future reference...

photo 1.jpgphoto 2-3.jpg

I'll let you know what happens and we'll go from there...
--john
 
The drawing is more complicated than it really is in reality. The connectors on it were made for the old style tach that plugs in with bullet connectors. Since your tach has screw down terminals, I think you will find that you are essentially, putting the grey lead of the resistor on the sender post of the tach and the black lead on the ground post.

If you have a set of jumper leads, you could just connect it with jumpers temporarily, before going through a lot of cutting and connecting.

Mike
 
Really, it's that easy? I don't think they expect the tach to have bullet connectors it's the harness that comes from the control box.
Do you really think it's as easy as putting this resistor across the tach sender and ground? Seems pretty easy.
 
The original tach that was shipped with these motor had leads coming out of it with bullet connectors coming out of it. The wiring harness at that time also had bullet connectors that would allow it to connect right up. No screw down terminals.

That is what is was designed for.

The resistor bypasses some of the current from the tachometer to solve the "problem".

Hope it solves yours.

Mike
 
SOLVED! Hondadude(Mike) thanks a million. You were right on the money right out of the gate. I did some testing back and forth on the charging coils. I couldn't really figure out if they were working or not. The tests were inconclusive. It was a combination of not having the right tools and not really knowing what I'm doing ;). Anyway I ordered that resistor assembly from honda (pictures above in the previous post) 06383-ZV5-315 Resistor Assembly.
It couldn't have been any easier to install. I simply followed the grey tach wire from the tach back to where it went into the harness. It was a bullet connector at the harness. I undid the bullet connector and plugged in one end of the resistor where I unplugged it and the other end into where it was plugged in. Basically put it inline. Then I followed the ground wire from the tach into the harness and did the same thing (basically put the ground wires in line). I know this is really easy for most people but I want someone else who is not so mechanically inclined to be able to do this as well.
I set the tach back at the 3c6p setting. Now this was the setting that was showing the correct top end but also showed about 2400k rpm at idle.
Well now this setting shows idle right around (hovers above and below) the 1k mark. When you rev, the RPM gauge goes all the way up to about 5900 RPM which is right on the money.
I ordered the part from boats.net at it was about $30 shipped. It completely solved the issue.
I started walking the dock and seeing other people who had the same engine and what their tachs were reading. Looks like most boat riggers forget this part and just set the tack so it idles at 1k. 4 out of 5 boats with this engine are topping out at 3k RPM. I ordered 3 more resistor assemblies this afternoon for my neighbors.
Thanks again Mike, it was an annoying problem.
 
One more thing...if your friends have a Faria gauge without hour meter, it will probably not work well. Again...I can not explain why, just my experience.

Also, their tachs have to be set at the correct setting for their motor.

Mike
 
What gauge do you have? What brand is it? Does it have a selector switch on the back? Post a picture of it, if you can.

If you have the original tach that was shipped with the motor in 1996, then the resistor in the above posts should fix it.

Mike
 
If your tach is working as described earlier in this thread and you have the Honda tach that has the wires coming out of the back with bullet type connectors...then order the resistor in the picture and installed it into the leads going to the tach. That should fix the problem.

If your tach does not work at all, then, that is a completely different issue.

Mike
 
my problem is that the engine starts and runs fine but when there is load on it can only get up to the 3,000 rpm
in neutral comes almost up to 6000 rpm
 
Well then, it's not a tach problem.
You should start a new thread describing your problem.

And don't rev it up to 6000 in neutral.
 
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