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2000 BF50 Tachometer issues

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Flanneldan9

New member
Hello,
I have a 2000 BF50 that I cannot seem to get the tach right on. This motor is on a 1999 Lowe FM 16-foot, so I'm not sure if it's original. The motor seems to run very strong, and after changing the prop to a 14 pitch, the WOT is just over 30 MPH with 2 people. I think this is good, but it's my first boat, so no experience. My issue is getting a good tachometer reading.

My dash Tach is a Faria with warning lights, and I have the back set to 6 pole. I can never get it to go over about 3k rpm, even though it is clearly running above that. I am struggling with the proper idle RPM, so I purchased TinyTach, but again, I can't get it to read right. When I set the settings to 1 spark per revolution on the TinyTach, it seems to be good at WOT with a reading of about 5200-5300 RPM, but at idle it will only go to about 1600 before it wants to die, and it sounds as if it is idling far lower than 1600. I thought maybe a cylinder was dropping at lower RPM, but it does not appear so, and the compression on each is at about 190 PSI, within 3 PSI of each other. I am starting to think maybe I have a CDI going out? I understand outboards have a funky charging system that can affect the spark, but mine seems ok. My batt was at 12.3 v and when i fired it up on fast idle it went to 12.8 v. Can anybody help me out with this or have any idea what I'm running into? Do these things maybe have a variable spark, like an MSD ignition system? I can post pics or videos as needed. thanks everyone!

Dan
 
Hi,
I'm absolutely no expert but, in my opinion, based on what I've seen over many years of boating, the 30 mph for a 50hp on a 16' aluminum hull with two adults is what I would consider a decent/good number.

If your tiny/tach is accurate, you might be missing 2 or 3 hundred rpm top end but that can be load related and not necessarily mean the engine is lacking any power.

Besides weight from equipment and personnel, even a dirty bottom or flex in the hull can skew those numbers. You are using the most aggressive pitch prop that's listed and that can move those numbers too.

Just my opinion but I think your rig is running just about right and there's no reason to suspect anything is wrong with the CDI.

If anything, I might look to make sure that the throttle linkage is properly adjusted and you're getting max WOT.

Good luck.
 
Just a couple more comments about things you mentioned:

Those compression readings look very good for an outboard of that age to me.

While you didn't say how many hours it's seen, the 3psi total difference between the three cylinders is excellent and indicates minimal wear with plenty of life left for rings and valves
The engine was probably very well maintained all these years.

12.8 charging voltage at "fast idle" is low in my opinion. Does the voltage increase as the rpms go up? I think 13.3 to 13.6 volts charging at 1,000 rpm would be the minimum I would want to see but it should not go higher than about 14.2 volts at any speed to prevent battery damage.

You should probably first evaluate the battery"s age and condition before suspecting a charging system problem though.

Just some thoughts.

Good luck.
 
Thanks for all the info,

When I bought the boat, the guy had not run it for some time (about 3 years) and could not get it to start, so it was cheap. I did a compression test at his house, and each cylinder was 155 psi. I bought it, and the carbs and fuel line were a mess. Rebuilt the carbs, and it has been great! After running it for a while and checking the compression with the throttle wide open, my psi increased to almost 190 (I was very happy).

The boat/motor had no hour meter until I added one. I am torn on the hours... the motor is very clean with almost no sign of use, and the boat is overall in great condition with original carpet, but the trailer has seen some heavy use, so no idea. The boat came from Montana at some point (now CA). Also, no clue if this is even the original motor, although it appears so, or was professionally installed.

The charger system does have me a bit concerned. I plan on doing an entire boat overhaul of carpet, floors and electrical in June through August, at which point I will likely convert everything to lithium (already slowly doing this, bought a Quest Minn Kota 36v with a large 100ah lithium batt), but for now I have several things running on the lead acid battery, including downriggers and two fish finders. I did increase RPM when testing the charging system, but literally for only about 30 seconds, and that brought me to 12.8. I am going out on the CA delta tomorow, and I think i am going to take a spare batt. Is there a better way to test the charging system other than at the batt?

As to the original question, I do think the motor is running very well. I used to be a mechanic and am still heavily involved in cars, and not having a working tachometer is a cardinal sin for vehicles. I know it is probably not as bad for boats, as they are designed to run at max RPM, but it is something I would very much like to have working properly. Thanks for all the advice!
 
Same here.
Retired ASE Master, L1, L2, Alternative Fuel and HVAC
for large paving outfit.
Trucks dozers, track hoes, cranes, scrapers, plus all support eqip...especially my service truck:>)

Started working on Honda TWINS about 08 after "retirement" as independent contractor to recreational lake boat rental fleet.
Finally got old & retired for real.

It's pretty typical that folks just park 'em with fuel in 'em and let 'em sit. The carbs stymie most people so kudos for dealing with those and getting her running again.

The charging system for your outboard is pretty light duty and mostly meant for keeping the storage battery up for cranking and some operating lights.

12 volt, 10 amp magnetic inductance (magneto) with rectifier/regulator. I'm not familiar with how "load tolerant" system is but want to reiterate that it won't perform well trying to push electrons through a compromised, resistive battery.

I have no experience with charging Li batteries other than my cell phone and power tools so I can't comment about how well that might go.

So, starting with making sure the lead acid batt is in good shape with no sulfate from sitting or age is wise before condemning any outboard.componts.

Good luck with the project.
 
The battery is not too old, dated January 2024. It is a marine battery, but it is sealed, and I always hate those. Seems to be holding a charge decently.

I will admit that when I saw it had three carburetors, I had a moment's thought that this was going to be a huge pain. I have worked on several "Six-Pack" (three two-barrel), mostly on Pontiacs, and they are always a nightmare to get just right. But these Honda carbs were super simple and easy to clean. I am not a fan of them being sealed, so you cannot tune them, but I guess it is some emissions thing. So far, been a good motor though.
Added some pic of the boat. Using it as much as possible before I do a full gut and replace. I want to get the feel of it so i put it back together just as I think it should
Forward.jpg
Boat.jpg
Motor Carbs.jpg
 
Nice looking boat. It looks very similar to my '83 Fishermarine 16'
A very comfortable and stable fishing platform. It's fairly lightweight and will launch in a little more than a cup full of water. I could fish when the water levels were down due to drought and the guys with the glass Rangers, Champions and Skeeters had to find something else to do.

When you say that the carbs are "sealed", I assume you mean the limiter caps on the idle mixture screws?
Those are plastic and come off with heat as they're held on with Loc-Tite. It usually ruins them.
The mixture screw heads have no slot as they are false heads and made to snap off if tampered with but you can carefully back them out with a sharp pick and then cut a slot with a Dremel wheel so that you can balance the carbs.

They don't have accelerator pumps. Quick throttle enrichment is done via the diaphragm that resembles an anti-stall dashpot. The diaphragm squirts fuel through a calibrated check valve that also acts as an anti-stall, reverse flow damper when the throttle is released.

The 50hp Honda has a unique induction muffler that will make noises that sound like engine knock at times. It freaks people out when they hear it but it's completely normal for that model.
 
I am so glad you mentioned that induction muffler! I have heard the rattle or knock. I knew it was not bottom-end noise as it did not increase perfectly with RPM, but I thought it might be some weird lower-end gear noise, to the point that I have been checking for metal in my lower unit after almost every use. I could not pinpoint where the knock was coming from. I normally only notice it in neutral at mid-range RPM, but it didn't sound great, and I couldn't figure it out. Thanks, man, this is very helpful information.

I have watched a few videos on the carb mixture screws (yes, that was what I meant). I do not think i am going to try and remove the caps at this point as the motor seems to be running great, but i hate that on a corborated motor I cant adjust my mixture. Again, regarding vehicles, this is something I am always tinkering with.

For the accelerator pump, I noticed during the carb overhaul how simple it was and how it lacked several features, which worried me. I will say, if I go from 0 to WOT, I have a slight bog in the motor. Not worried about it, as I switched from an 11-pitch (no bog) to a 14-pitch and knew what was causing it, but I am going to look at this anti-stall system you referenced just so I can better understand the motor.

Thanks again for the information; this is very helpful.
 
You can check the charging coil to see if it's producing voltage by unplugging the harness and probing the wire connectors where they protruding underneath the flywheel.
Item 3 in the link below.




If the coils are producing adequate volts and the charging is too low, check for voltage from coils at plug connectors for the regulator...item 2 in link below ...
...make sure regulator ground is clean and that grounding terminal and mount bolts ...items 39 and 43...are tight.
Luckily, they still sell the regulator if needed.

 
Yes, I thought you might ask about the knock. It's a common head scratch for most new owners. That info is in the Honda Marine Carburetion Manual or, otherwise, I wouldn't know about it..

I gotta say, you got VERY lucky with those carbs. Actually, they can be a BEAST to get properly clean if badly plugged. Kehiin made them to provide performance as well as offer thrifty fuel consumption so there's precision in the build

I will bet my favorite pair of tennies that the previous owner ran high quality fuel and it was stored with a stout dose of stabilizer in whatever gas was left in the system. Either that or it really didn't sit all that long at all.

The metering orifice in the low speed jet set tube alone can have you crying the blues trying to clean it. That is, IF you can even SEE if it's plugged. Sometimes replacement is the only cure but parts are getting harder to source and expensive.

If you develop starting or idling issues, you will be forced to pull the mixture screws to make absolutely sure that the low speed circuit is properly clean. There's no other way to get at the entire system. Because these are "cascade" delivery carbs, they won't provide full fuel if the idle circuit (or intermediate) doesn't deliver it's maximum share at WOT.
Your complaint about the idle not being satisfactory could be pointing to the mixture screws as it is. While I agree it's truly a.PAIN to futz with those, I never leave them be when cleaning a carb.

As to the bog, check that the diaphragm pumps fuel when the rod is depressed and that there are no tiny leaks in the tubes. Those tubes crack and split as they age.

Good luck.
 
If your idle is in the 1650 range out of gear, I would think it would make a big clunk shifting it into gear?

In my Pontiac and Honda FI outboard I run 91 octane only, non ethanol, am very careful where I buy my fuel, and liberally use Sea Foam in my gas. I also run them both at high rpm under load as much as possible, my theory being the hot running keeps fuel passages and valves clear of varnish. The previous owner may have done a lot of low speed trolling and or not been careful with fuel quality. So run it as much as you can above 3,000 rpm for a while, see if anything changes?
 
I just read my last post about the enrichment/anti stall diaphragm. I wrote that it pumps fuel. That's wrong! It pumps air! NOT fuel! The tubes will leak AIR.....NOT fuel!

Getting old.
Sorry.
 
Hey everybody, sorry, just getting back from the delta. Only one striper (target fish), but we did land a 6.8 lb largemouth, so it was a good day! NSDON, beutiful Ponitac! My dad owned an automotive shop that I worked at for several years, and we specialized in classic vehicles. Pontiac was both our favorite. He had a 67 GTO with the six pack, and I hated the damned thing! What model is that one? Is it Canadian only?

Jgmo, I think you are right, and I need to go a bit deeper into the carbs. For sure, it had sat some, and when I got it, and it would not run, the middle carb main jet was completely blocked with gunk. My idle RPMs have been giving me issues, and I think I may not have fully understood the carburetor or missed something. Also, when I pull one plug wire at a time on the top and bottom cylinders, the engine drops sharply in RPM and dies within seconds. On the middle carb, it is not as dramatic, and the engine will power through. This might indicate that this cylinder is already not running at peak performance, correct?
 
Flanneldan9,

Yes, I think that you're probably right. What you did is what is called a "cylinder contribution test". It does sound as if #2 (middle) cylinder might not be doing it's fare share.
And, that could very well be the carb based on what you say about the conditions you found when you first started working on the outboard.

There are plenty of "nuances" to cleaning these carbs up effectively after they've been contaminated. Little things that even guys with carb rebuild experience from working on cars can't guess or know until they've struggled working on them.

A truly spectacular individual, the great hondadude, who contributed to this site when I first joined, schooled me on MANY things Honda and one lesson was to get myself a copy of the Honda Marine Carburetion Manual. He told me that he too had trouble with these Kehin carburetors before reading that manual. After having learned so much from him about Hondas already, his recommendation was all I needed to convince me to buy it. I have never regretted getting it. Lots of carburetor basic theory which is very useful in a general sense and, while probably not perfect, it contains much of the specifics needed to understand what these carbs need to function properly.

I now have two editions of that manual because I ended up working on so many of those little boogers when I had my business.

Ok, sales pitch complete.
If you're interested in getting a copy, you can find it here under Support Materials:

Honda Marine | Shop Manuals Publications | Honda Power Products Support Publications

publications.powerequipment.honda.com publications.powerequipment.honda.com
 
1963 Parisienne Dan, the Cdn Pontiac used Chevy frames and mechanicals in these years. This was much like a Catalina body wise, the hood scoop was used on the 63 Catalina Swiss cheese cars. In 63-64-65, you could get a twin carb 425 hp 409 from the factory. More factory hp than any other Pontiac whether 389, 421, or 455.
 
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