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2019 Honda bf 150 stumbling issue on port motor, case.

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Bustedknuckle

Member
Setup: twin bf150s on a clearwater 2508, non ethanol only, both motors are on separator water/fuel separators.


Hours : Around 200


Symptom: On 1st run after getting on the water I put it to WOT and Engine gets up to 4500 rpms and planes but then the port engine starts to stumble and sputter. I have to pull the throttle back to less than 1200 rpms to run continuously. Any more throttle and it will stumble. Even with the rpms less than 1200 rpms, you clearly see the port engine shaking more than the starboard engine. No engine codes

Tests:
1. Fuel pressure test: Readings- without key priming- 30 PSI , with key to ignition -priming to 45 PSI then goes to 40 PSI, start and run PSI- 38 PSI @IDLE.
2. Unplugged coils 1 at a time engine responded on each coil unplugged.

3. When I'm on the water and symptoms occur I will go to pump the bulb and it's hard and doesnt take more fuel when pumping it.
4. Fuel RPMS in water in neutral-no load


Untested: fuel pressure test under load. Spark plugs haven't been pulled.


Replaced- fuel bulb, high (OEM) and low pressure (aftermarket amazon) filters, high pressure Fuel container/strainer, outside of motor water/fuel separator looks great, the OEM water sensor doesn't have water in it, and the VST float operates normally. When examining the VST it looked mostly clean
 
Bustedknuckle said:
Setup: twin bf150s on a clearwater 2508, non ethanol only, both motors are on separator water/fuel separators.


Hours : Around 200


Symptom: On 1st run after getting on the water I put it to WOT and Engine gets up to 4500 rpms and planes but then the port engine starts to stumble and sputter. I have to pull the throttle back to less than 1200 rpms to run continuously. Any more throttle and it will stumble. Even with the rpms less than 1200 rpms, you clearly see the port engine shaking more than the starboard engine. No engine codes

Tests:
1. Fuel pressure test: Readings- without key priming- 30 PSI , with key to ignition -priming to 45 PSI then goes to 40 PSI, start and run PSI- 38 PSI @IDLE.
2. Unplugged coils 1 at a time engine responded on each coil unplugged.

3. When I'm on the water and symptoms occur I will go to pump the bulb and it's hard and doesnt take more fuel when pumping it.
4. Fuel RPMS in water in neutral-no load


Untested: fuel pressure test under load. Spark plugs haven't been pulled.


Replaced- fuel bulb, high (OEM) and low pressure (aftermarket amazon) filters, high pressure Fuel container/strainer, outside of motor water/fuel separator looks great, the OEM water sensor doesn't have water in it, and the VST float operates normally. When examining the VST it looked mostly clean
Click to expand...

A few questions:
1. If engines only have 200hrs, does boat only have 200 also? Or are these a re power?

2. Shared fuel tanks between both motors or separate fuel tanks?

3. Do the spark plugs have 200hrs on them as well or are they new or 100hrs?

4. On the items you replaced, was this before or after the issues started?
 
1. Boat is a 2019 and same hours
2. Shares 120gallon tank
3. Orginal 2019 oem plugs
4. Started after low pressure and high pressure filter replacements. But sat for 9 months beforel testing this year. Same service on my starboard motor and it runs fine.
 
Bustedknuckle said:
1. Boat is a 2019 and same hours
2. Shares 120gallon tank
3. Orginal 2019 oem plugs
4. Started after low pressure and high pressure filter replacements. But sat for 9 months beforel testing this year. Same service on my starboard motor and it runs fine.
Click to expand...
Very well could be plugs. 200hrs is getting up there on a set.

I would do that and check the fuel pressure while running it to get the fuel pressure when it does studder.
 
after it stumbles and you shut it off does it restart and seem to idle ok ?
If it restarts and idles fine and only under a load that it stumbles again then it sound like a fuel delivery issue and could be oring to high pressure was reused. that oring tends to grow in size and gets pinched when reused. or the Oring on the low pressure filter is letting air by, but has enough seal to keep from leaking. Pull off and inspect for flat spots on that one . if that doesn't fix it put fuel pressure tester on and run it til engine starts to stuble. Even though you only have 200 hrs it could be overheating worn fuel pump likely cause by running the pump when changing the filters without priming them first.
 
HonDan said:
after it stumbles and you shut it off does it restart and seem to idle ok ?
If it restarts and idles fine and only under a load that it stumbles again then it sound like a fuel delivery issue and could be oring to high pressure was reused. that oring tends to grow in size and gets pinched when reused. or the Oring on the low pressure filter is letting air by, but has enough seal to keep from leaking. Pull off and inspect for flat spots on that one . if that doesn't fix it put fuel pressure tester on and run it til engine starts to stuble. Even though you only have 200 hrs it could be overheating worn fuel pump likely cause by running the pump when changing the filters without priming them first.
Click to expand...
Yes, starting is no issue and stumbles after high delivery of fuel and doesnt recover fully. Will run at lower rpms but shakes.
 
Try letting fuel out of the vst drain screw into a clear jar see if any water comes out with the fuel?
Bad plugs make the engine hard to start have to crank away on it, they are iridium and last a very long time. but pull and check them anyway and use anti seize putting them back.
I read you checked each coil but did you also try each injector one at a time?
Disconnecting a good one will either kill the engine or make it run real bad the one that doesn't make the engine run worse is the bad one.
 
Update: I have denso plugs in the bad motor. My other motor has ngks and runs fine. I have ordered all new ngks, and oem low pressure filter and orings.

I like that idea about the injector. I will try that out! Never thought about that.

Compression test looks good. Less than 5% variance.

Also I only have over 100 hours not 200. Im not sure why I said 200. But would just 100 houra on an 2019 engine need a valve adjustment?
 
With only 100 hrs you shouldn't need a valve clearance check yet. Think book says 600hrs they tend to wag at idle with those hours indicating need for adjustment but still run fine.
 
I'm wondering since the boat actually only has 100 hrs on it, and it's 5-6 years old, it sat for 9 months, how old is the fuel in the tank? Was it stored full or half full? I know it's a shared tank, but if you started port motor first like me, it could have sucked up bad gas or debris off bottom of tank.

I mean if your only putting 20hrs a year or less on, the fuel could very well be from 2022, mixed with previous years

You said vst looked clean, did you actually disassemble or just drain it?
 
codycat said:
I'm wondering since the boat actually only has 100 hrs on it, and it's 5-6 years old, it sat for 9 months, how old is the fuel in the tank? Was it stored full or half full? I know it's a shared tank, but if you started port motor first like me, it could have sucked up bad gas or debris off bottom of tank.

I mean if your only putting 20hrs a year or less on, the fuel could very well be from 2022, mixed with previous years

You said vst looked clean, did you actually disassemble or just drain it?
Click to expand...
Boat is a 2019 and same hours. Vst disassembled and fuel pump strainer/container replaced. Made no difference unfortunetly.
 
UPDATE: It was 100% a bad denso plug. Replaced with ngks, and it ran excellent yesterday. Ty for asking I meant to post this earlier. Thank you all for your guidance.
 
Bustedknuckle said:
UPDATE: It was 100% a bad denso plug. Replaced with ngks, and it ran excellent yesterday. Ty for asking I meant to post this earlier. Thank you all for your guidance.
Click to expand...
That's great news!

Kinda curious, if they were the original OEM plugs, why 1 motor had Denso and the other had NGK?

Anyrate, glad it was a simple fix!

I'm assuming since a twin setup, you do alot of trolling. I noticed on my suzuki previously, about a 100 hrs it's time for a plug change
 
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