1996 BF50 Honda Bogging out when trying to plane

[MattFL]

I haven't had the head off of one of these things myself, but I believe @ahicks has worked on a ton of these. Unfortunately it looks like he hasn't been online here since 2023, I hope he's OK. If you did the descaling rinse, my guess is it's likely cleaned out good at this point.

 

[Noah4200]

Awesome..thanks again. I just saw the top cylinder is like 165-170 in the driveway where the lowers are 145-150. Overtemp is like 195 so i was concerned about WOT but im guessing it cools much better IN the water than on a hose without any holes plugged up and may also run cooler underway with more volume flow at higher RPM than idle.

 

[Noah4200]

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 ?

 

[Noah4200]

I guess resistance at rest and room temp isn’t that valuable anyway…more about voltage output when warm under load. Just gonna swap it…that will be everything. Just disappointed not to have hard evidence

 

[Noah4200]

Even with a new high end MM i still couldn’t get nearly any of the readings to be right on either CDI and they were consistent amount the 2. Something is not right with the ability to take proper measurements as described by Honda in the service manual. Completely useless. Will go ahead and swap to new CDI and go test with that and the new fuel pump. Those are 2 major culprits and the last 2 components remaining. I’m confident with the carbs and top end so there is a very good chance this is over. If not it’s gonna get really weird and ugly from here. Would have to be an intermittent ground or connection or failing seal or gasket. I’ll take a laser temp gun just to check cylinder head temp. As stated earlier the old fuel pump had a leak after testing. Please let this be over!!!

 

[MattFL]

Hopefully the new CDI will do it. If the seller had a lot of good feedback then odds are in your favor that the new one is probably OK. I'll keep my fingers crossed.

 

[Noah4200]

Thanks matt. I got it on and started in the driveway..everything sounds about the same. Will bring it to test ASAP. Just for the heck of it i jumped the thermo sensor lead to ground and NO buzzer or over temp light still. As i said im getting continuity from the sensor and rear ground clear to the indicator on the helm. Don’t understand what the problem is. The red light was clearly on last week (but no buzzer) when i suspected overheat and flushed the motor. Buzzer sounds when jumped on 12V too. Can’t help but think this may be part of what’s going on here. I’ll take my laser temp gun and if it still acts up and IS NOT hot i will disconnect the thermo sensor.

 

[Noah4200]

I checked the blue/yellow to the buzzer too. Has continuity. So the gray wire from the indicator lights that goes to the multi panel is the only unknown. Red checks, yellow checks, and ground checks to the warning light plug. Looks like the red from the temp sensor splits and goes to the CDI and light. So it should illuminate separate from the cdi..i assume the cdi handles limp mode and the buzzer. So if my warning light bulb was out/intermittent i would assume buzzer should still trip.

just want to be able to know if im ever overheating

 

[Noah4200]

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.

 

[Noah4200]

so either the temp sensor input path to CDI or buzzer wire output from CDI have a problem. Bc the trim control buzzes no problem and is tied into same wire up stream. I’ll use my pinprick prob leads and see

 

[Noah4200]

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?

 

[Noah4200]

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.

 

[Noah4200]

Ok it’s ready for a sea trial. One last thing i’ll mention that gives me GREAT hope is that today i did a cylinder drop test and the middle cylinder affected the running exactly as much at the top and bottom. This is very good news as when this all started i posted that i didn’t think the middle affected thing as much and blamed it on being more “balanced” in the center position. It’s very severe now…all cylinders are. I’m extremely nervous about this test as i feel i’ve covered everything. will update

 

[Noah4200]

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!

 

[MattFL]

Excellent job sticking with it, hopefully it will run for a very long time.

 

[jamessshelby]

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!

 

[jamessshelby]

Noah, I normally go on Marine Engines Forum, just now picked up boats. My experience over the last 2 years is almost exactly yours except I have twin 1996 Honda BF40a s. Problem started with my port engine surging at higher power. I have owned them since new in 1997 and they are fresh water engines, never corrosion problems. My whimsical thought was that I could swap parts from my starboard engine to see what works, no such luck. Seems every time I try something things get worse. I am going to work on both of the engines shortly and would like to communicate with you and the master petty officer as I progress.

 

[ErSa]

Great detective work and patience Noah4200!
Interesting reading.