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1997 HONDA BF50a RUNNING DETERIORATING AFTER 5 MINUTES !!

N

Noah4200

Contributing Member
Guys i’ve been trying to get my motor working correctly all year and have done nearly everything. Is older but only about 1000hrs. It starts out running perfectly and then quickly goes downhill after 5 minutes on plane. It’s not overheating…temp alert works correctly (was overheating before an intensive acid flush)…fine now. Just did a meticulous carb clean…i mean whole carb in ultrasonic machine with warm carb formula multiple times, air compressor, carb cleaner thru all fine circuits multiple times. Covered individual fine holes and flushed thru pilot circuit both ways and confirmed output. All needle jets were replaced last cleaning but i even made sure they were clear again. Checked float height…new orings with a bit of silicone grease. STILL bogging out after running and getting worse and worse with time to the point where even off idle to 1700 rpm is rough and barley getting back to dock. BUT NO OVERHEATING. Fresh ethanol free fuel. ALL new OEM hoses and prime line. I mean i checked dashpot and everything. Already swapped all 3 coils, pulser coil, exiter coil!!! Compression 190-195 PSI on all cylinders. All that is left is fuel pump and CDI. Fuel pump is original diaphragm pump from 1997. I mean 27 year old pump with rubber diaphragm. Pumping the bulb actually seemed to make it worse when underway. Should i go ahead and just do the fuel pump? Each time i take it out it seems to get worse and worse. Here is a clue from this time- it’s intermittently trying to run strong. Every 5-10 second power will return. As if struggling for fuel or spark (deteriorated pump or CDI component deteriorated). Its HAS to be a trashed fuel pump diaphragm or failing CDI circuitry rapidly degrading with heat. With the control lever constant…listen to this video today-

 
Hmmm.

Your spark plugs might have a story to tell. Give them a look.

I agree with you that it might be the fuel pump but just a guess. I don't have a manual for that one so can't tell you how to check fuel pressure.
Make sure it isn't leaking gas into your engine oil!

Other ideas are....

Is it maybe running TOO rich? I mean....is your choke system assembled and operating correctly? Linkage all connected? Blackened plug ends would point that direction.

Are you running a remote fuel tank or in hull?

If in hull, maybe something wrong with the pick up? Or, something floating around in the tank?

Try running on a remote tank if possible.

If you are already using a remote tank, same thing....
Check fuel pickup tube and tank vent. Check for "floaties" that could block pickup. Run with fuel cap loose/off to see if it changes anything.

You say it runs ok but then starts crapping out after 5 minutes....
...could it be an air intake leak developing as the engine gets warm?

Did you use new gaskets when doing the carb installation?

Try running it with the hood off (and secured! They WILL fly out and they DON'T float!)
When it starts bogging down, try spritzing some carb spray around the intake manifold to see if that makes a difference.

Did you get the dashpot check valve put on correctly?

Sorry, no silver bullets but, hopefully, my questions will ring a bell for you.

Good luck.


.
 
I know you said that you checked the floats but watching the video again it does seem like it could have one sticking.

It takes all three carbs working together and that does bring up something that you didn't mention ....synch.

Did you synchronize the carbs?
I'm not sure not doing so would cause that same symptom but you never know.
 
Try pulling one plug lead off at a time, if one cylinder is playing up you will be able to identify it, that should be your starting point
 
Ok i ordered a new OEM fuel pump 85$ shipped great price. BUT honestly this whole time my heart has said CDI. Have just avoided they are not available new really and 300$ used even. Mine cosmetically looks great (but i know that means nothing). Seems with a bad fuel pump after sitting and pumping the bulb until hard the bowls would have to be full and give me another brief period of running. The only exception is that failed diaphragm pump can send a TON of air into the carbs creating a frothy mess as soon as engine is started…but i would still think it would run ok for a minute. Yesterday i sat with the cowl off for an hour at anchor and it still immediately felt terrible upon starting. I would think that the CDI would be cooled down AT LEAST as much then as the 5 minute off plane cruise off the dock where i was still able to plane with full power breifly. So here are my options:
1: measure out float bowl volumes at cold start and then after problems and compare to rule out fuel.
2. Get some sort of tool to measure spark at each cylinder WHILE running poorly. Maybe some sort of inductance tool? Can you use a DVM while running? I need something capable of giving me an on the fly reading/indication. This would finally rule out electronics!!! Should have done this long ago.

IF both those check out ok…then i may be dealing with something very serious internally that is letting loose as engine expands. Not running right after an hour cool down concerns me…i would think fuel pump rubber and CDI would recover with that amount of time. Where as engine heat soak would not.

What is my best bet for on the fly spark test?
 
how about 3 of these and shoot for a cloudy day?
IMG_2357.jpeg
 
In my opinion I don't think your outboard is suffering any onset of internal failure here. Did you try the carb cleaner spritzing I suggested?

If you suspect it's losing spark, you could simply hook up a timing light to each cylinder briefly.
That IS an induction tool that you can use while it's running.

But I like Ian's suggestion of pulling plug wires one at a time.

In auto mechanics we call that a cylinder contribution test.

Little or no change when you pull a wire identifies the weak/non-contributing cylinder.

One thing that makes it much easier to do is to remove each plug wire and coat the inside of the boot with a thin layer of dielectric (tune-up) grease before testing. Makes them come off and go back on the plug end with little effort.

Use a dry rag or leather gloves if you don't have plug wire puller pliers.

CDI is the LAST place I would go but I do think vibrations over the years may have loosened a connector socket or two. You should inspect those closely.

Tightening up suspect sockets and giving the pins a very slight twist with a small needle nose plier is a time honored trick for improving contact along with a generous amount of De-Oxit contact cleaner.

Also, those connector pins and sockets are crimped on to the wire ends. Over time those crimp connections can succumb to corrosion. I have seen them be still connected by only one or two strands of wire and that can interrupt current flow.

You are at a place where load testing each and every wire might reward you with finding the one that is causing you grief. It is a tedious chore but I would certainly do it before spending hundreds on a used CDI that could turn out to be worse than yours.

I unplug both ends of the wire and power an old style, sealed beam, headlamp through it and then gently pull, wiggle and twist while watching the light for any sign of flickering.
Lots of work but you will have no doubts when done.

I know how frustrated you are so I'm definitely hoping you find a solution soon.
 
OMG GUYS!!!! I tested the thermos switch for the heck of it today and it was not working on the panel, so I confirmed that signal was getting up to the helm and ground and it was and it got me thinking about the CDI again so I decided to go ahead and pull it off and test it. IT FAILED EVERY SINGLE TEST miserably like we’re talking 5000 to 8000 ohms when it was supposed to be 10 to 500 some of the legs didn’t even have continuity. I’m surprised the boat ran at all. When warm i bet the measurements were off the charts! I guess because of the unavailability and cost I avoided testing it (also thought it would only show bad when hot) because I was also told from a lot of pros that they’re very durable and rarely fail, but this one is absolutely trashed. CASE CLOSED. Thank you so much guys! A year of hell is over. I’m going to source one and get back on the water. I did see a place that looked to have a new one for like 550$. OUCH 🤕
 
I’m sitting here in shock LOL…threw everything but the kitchen sink at this thing. Saved in the last quarter here today…about lost it hahahaha
 
One last note i had the magnet delamination when i first got this motor and was knocking the coils…i bet those pulses helped to destroy this CDI. I’ve probably put 1300$ this motor at this point but i guess it’s cheaper than a used F70 and sips fuel. HOPEFULLY I get some decent life out of it. Will let you guys know when i get the new CDI tested
 
Just for clarity…I noticed the CDI table in the service manual says (KOHM) for the units. Was disappointed bc i thought mine might not be bad but I am getting 2-5 MEGA ohm when i measure. This would be 2000-5000 kilo ohms which is out of the 5-500 kohm range. In addition some of the circuits are showing non continuity when there are ranges listed. Again, looks to be a bad CDI.

Would this also explain why my alert system is not functioning correctly (overtemp light not working when shorted (even tho red and ground show continuity to the indicator), came on last week but no buzzer (even tho buzzer works for trim alarm/and also with 12v connected)?
 
Allright terrible news…the CDI that arrived shows mega ohms too. 5 mega ohms. Which is 5,000 K ohm. Specs say 5-500 K ohm. This is all really upsetting. I read another forum where i guy was getting Mega ohm.
None of the specs in the manual are right for me. Either i have 2 bad CDI, a bad MM or the factory specs are wrong.

No returns on my CDI as well.

Can anyone help me confirm the correct range for the CDI specs ?
 
So after some research sounds like due to the nature of these CDI they are hard to test with a standard multimeter. Found lots of cases in different honda motors where people are getting mega ohms where the manual clearly says kilo ohm. I even purchased a 100$ meter today and still get mega ohms. There are legs also where i am getting nothing according to manual but if i reverse polarity opposite from what’s indicated in the manual i get a reading…but still seems off. Really not impressed with the whole CDI diagnostic chart from honda at all. Like i said earlier i wasn’t expecting CDI to show bad resistance wise at room temperature anyway. So im going to put the new CDI on and will go test the boat again with it and the new fuel pump. Those are the 2 big final culprits and if it still starts going downhill i’m not sure even what would be next…that will have been everything gone though. I’m confident with this fuel pump that fuel CANT be an issue (all new lines, carbs done 3 times spotless). All electrical components have been gone through also, but there could be a bad connection somewhere. I’ll bring a laser temp gun to rule out heat. Passes compression but i guess a leak down test might still be on the table (head gasket when hot but doubt it).

So all in all guys this has really been bad and i’m just hoping it runs…i mean there is a real good chance the issue will be gone. I don’t want to investigate any deeper…it’s gonna get weird from here. I NEED this to be over.

Noah
 
Testing a cdi with a resistance test in my opinion is the worst test there is. Mercury recommend a dva meter and test voltage output with the engine running. You should get around 5 volts from each trigger coil (I have known a few of these to fail), and a min of 100 volts at the terminal into each ignition coil..All these can be tested using a sharpened paper clip to back probe each terminal then connecting your mutimeter through a dva( direct voltage adapter). This definitely sounds like a cylinder dropping out.
 
Just to add to this, tie the boat up well on a dock and do all these tests at the dock with motor running under moderate load.Do a cylinder drop test too while you're about it. If a cylinder is dropping in and out then when offending cylinder is disconnected, the revs should remain constant with no surge
 
I really appreciate the response. This Cdi will be every component swapped so will be interesting. Not sure what to do if it still acts up. I’ve tested most all wires and grounds around motor and all are ok. Will report back
 
With the swapped CDI the temp warning light still isn’t lighting when i jump the signal wire to a grounding point off the sensor. There is continuity to the signal wire and ground from the engine to the indicator plug up front. Buzzer works with 12v too and works for the trim alarm. The signal wire is split to go to the indicator bulb and the CDI (which would handle the buzzer and limp mode). Neither are working. Even checked the blue/yellow wire from CDI to buzzer and it had continuity. This is the same wire that comes from the trim control unit that is working and sounds the buzzer. Both CDI failed to light the overtemp or buzzer. Very strange
 
Ok i swapped the Red and yellow and grounded temp sensor and oil light went out so i think it’s the red bulb that’s malfunctioning. Now the question why is buzzer working for trim sensor but not overheat. Both are tied to Y/G. Signal to sound buzzer should come from CDI with temp sensor grounded. There is continuity.
 
So i jumped the CDI Y/G output wire that is in charge of buzzer activation during overheat/low oil and buzzer worked. When i jump the red temp switch wire to ground i’m not getting any change in the Y/G CDI buzzer output. There IS continuity to the red wire on the alert system plug on the CDI with R,Y, Y/G and Bl. This leads me to believe the warning circuit is not functional on this CDI. Well it wasn’t on the last CDI either. That’s hard to believe. Does the alert system not work in neutral or something? Like if you overheat under way and move the lever to neutral is the buzzer supposed to stop? This is my only explanation for this. Why would this circuit not be functional on multiple CDI?
 
HAVE NOT RUN THE NEW CDI YET. Hunted around all afternoon. Neither shorting the oil or temp sensor wires to ground point triggers the buzzer. Once again my conclusion is that BOTH CDI have a problem with the buzzer/limp mode leg internally. All runs on the boat have continuity and are in really good shape. I even tested the regulator (even though i’m charging fine 13.5 -14v) and all resistance specs on that aren’t right from the manual either. It also says tachometer gray to either coil gray should have continuity and only one does. This makes no sense either bc you would only need one input to tickle the tachometer. I can’t see if i’m charging correctly that my regulator would be affecting CDI or running. I did test my red temp bulb up front and found it’s bad. So i hooked that output to my buzzer so now the temp switch will trigger buzzer without CDI. At least i will know (won’t be in limp mode).

2 big things im pondering-

1. Should i bother trying to return this CDI for the warning system not working. I paid 270$. As i said i directly tested input and output…temp signal going in- NO grounding happening on Y/G buzzer output. I don’t see anyway it’s not CDI internal but it’s strange both CDI had this issue (unless it’s prone to failure).

2. I watched a video of my motor when i first got it idling and it wasn’t shaking nearly as much as it does now at idle. Ive tuned this thing up and synced it and done a lot and cant figure out why that would be. Timing marks dead one…valves adjusted properly. Carbs done 3 times. New flywheel. Really weird. My only thought was maybe it was related to taking the lower unit off and the adjustment of the lever is slightly off causing the cog/boss to drag or something but shifting seems ok. Why would my motor be shaking more? BTW there are NO extra lines to pinch on my 1996 model while syncing.
 
It worked!!! It was the CDI. I know they are robust but i think my old delaminated flywheel magnets hitting sent nasty waveforms and fried it when i first got the boat. Runs great! Ran all evening at every throttle level and not a single hiccup. Much more power now 4-5 mph faster top need. So damn relieved thank you for all the help.


Hope this helps someone in the future... what a journey!
 
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