Logo
FULL SITE MENU

BF150 Fuel Ratio adjustment

P

PaulBF150

Contributing Member
My BP150 engine is running lean I believe and is generating extreme exhaust temperatures.
Just an FYI the entire water system has been replaced and internal water passengers cleaned as well.
However, assume that cooling is not the issue.

Since the engine is controlled by the ECM based on multiple sensors. I'm looking for the one that alters fuel/air. Likely the 02 sensor in concert with MAP and BAROMETRIC.

If the engine is running Lean and further Leaning with VTEC engaged, what sensor fake out to so the ECM will increase fuel into cylinders and thus cool down combustion?

My guess the excessive heat is due to the engine running too Lean, so like to change fuel injection somehow to maybe get it to run a wee cooler.

Note: Engine idles, runs, accelerates just fine until the Exhaust Temp Alarm is sounded and I have Engine shutdown.
 
Hi Paul,

Well, first off, I would advise not to assume. If it's actually overheating, it could still very well be an issue with the cooling system that you just aren't aware of...yet.

Diagnosis should start with verifying the problem.

Is it ACTUALLY getting hot or is the PCM just saying it is?

A faulty engine temp sensor or it's wiring could be sending false info to the computer.

This is where a good infrared heat gun could come in handy to monitor head, block and exhaust temperatures.

Often, the condition/color of the spark plugs will tell a story.

If you think it's lean, you should check fuel pressure to ensure that the pump can provide adequate flow during hard acceleration and heavy load.

If the pump is good and you still want to "fatten up" the fuel mixture, pulling and plugging the vacuum line to the fuel pressure regulator (FPR) will richen it up at cruise. But it won't idle well for long and you mustn't leave it that way as it will foul the plugs and carbon up the valves and combustion chamber.

Good luck.
 
jgmo,
The Exhaust water temperature trips the alarm at 200 degrees F. I have an independent computer measuring all 4 Temp Sensors. Only the Exhaust cause engine shut down. When I see on my computer the exhaust climbing into the 190 F range, its too late I heat 200F and subsequent shut down. At Idle no issue, getting up on plane where engine is working hard is where Temp increases, especially when the VTEC comes on line. If I hold the RPMs down where exhaust water temp is around 160-170F I'm good but I loose speed. I have a second 150 that runs fine and takes much of the load from the overheating one.

I am preparing to check vacuum lines and replace all torrmorrow when I get them. As for fuel Pressure (HI Side) rans at idle about 125psi. Haven't measured underway, though. I too was thinking of putting hand vacuum pump on the fuel pump regulator to see what happens.

What confuses me is the fuel pump regulator is vacuum controlled by intake vacuum not an exact thing. Obviously the vacuum is caused by the valves, so Air coming into intake is controller by Throttle and the MAP reports to the ECM the air pressure. I assume the Barometeric MAP the ECM measures so it can offset intake air pressures if need be. I measured it and compared to the other engine, both about the same. So I thought if a make the ECM think it is what (this is where I don't know the BARO ranges) below sea level or at high altitude (not sure which way to go to in richen to combustion mixture.

Also another assumption, Richer fuel mixture will cause engine to run cooler, not good on fuel consumption or emissions, but I can deal with that.
Anything else I can do to make engine run cooler? (I confess I did Mac Gyver an external high pressure water pump into exhaust manfold at the top inspection port. It helps.
 
Well, I still don't know how to search this new format but it seems that you've been chasing this issue for a while. Either that or you're the second guy to install a water pump for the E manifold.

Have you tracked the exhaust temps on your good runner for comparison?

I seen a few posts here for the higher horsepower outboards where the engine overheats and the solution ends up being the pressure relief valve. Any chance it's something like that?

I'm afraid I just don't have the experience needed with this outboard to be of much help to you with this.
 
That is likely me! Yes, chasing this now for 3 seasons.
Actually, I disabled the relief valve (forced it to be always closed). Figure no point in dumping good cool water back into the sea!
I've had the head off twice (season 1 & 2) made sure all water passanges are expelling water as I pumped it through end water up tube .
I seen a recent post about a grommet in the oil pain for the water pump tube. I have no oil in the crankcase nor oil out in the water, so I assumed the seal is still good.

I think I addressed everything to do with cooling, so that is why I'm looking into Fuel mixture.

I think it going to rain cats and dogs tomorrow so anxious to try controlling fuel pump regulator. Maybe Sunday.
 
Firstly, your motor was not running lean. Fuel pressure should be 44psi with no vacuum. At idle, the vacuum causes the fuel pressure to drop to around 36psi. Exhaust temp sensors measure coolant temp, it has nothing whstsoever to do with fuel mixture. BF150s always have very white spark plugs indicating very lean by old standards, however, this is normal for these motors. You have a water flow issue here which can be caused by numerous things including clogged water passages around the cylinders ( fairly common on saltwater engines and usually necessitates head removal), and faulty block thermostat, excessive build up around internal exhaust anodes causing a restriction in the exhaust water passage. I don't understand your 125psi fuel pressure, that's so high the engine would be very fumey with very rough idle and sooty black spark plugs. Hope this helps.
 
Just rereading your last, the poppet valve is designed to allow more water to pass through the system at high rpm, sealing it off exacerbates overheating at high rpm.
 
Understand most of it. To address fuel pressure that is the High side to ejectors. I never measured the low-pressure pump out, but The High-pressure pump is pushing the 125pai it is getting ample fuel from low pressure pump, I would guess. Did not observe any significant change when removing vacuum line of either engine at idle, will check during test ride.

When I view the diagram in the manual pg 19-3 it shows the Pressure Relief valve returning excess pressure down to the lower end and out. The diagram does not should a passageway other than input from water pump to out back to the sea. Thus, the name Pressure Relief.

I just measure the vacuum on both engines by disconnecting at the fuel regulator. Bad Engine had a reading of -25psi and good had -20psi.
Go to try swapping the BARO, MAP and O2 of both engines, then go for test ride.

As for water flow, all is clear and clean (did remove head, replaced thermostats, exhaust anodes were pretty clean but replaced with new anyway.)
 
I would forget the fuel issue, it is not causing overheat. Try swopping out temp sensors.I have had faulty block temp sensors trigger alarm prematurely. It is the one located next to the oil pressure sensor above the oil filter
 
Also just confirm your thermostats are in the correct position, 60 degree closest tp the block and 50deg closest to the cylinder head
 
I have replaced all of them. I found when I vary the voltage output of each temp sensor (connect resister box to create voltage divider) the only sensor that causes engine shut down is the exhaust.

I have an A/D measuring each sensor to get real time temp value.

And yes I have the thermostats in correctly. and actually, changed them around and having known at all. No improvement, so back to normal configuring.

Test drive today did not show any improvement. Swapped 02 and MAP.
Did notice a big drop in vacuum around 4000RPM reading around 5-10psi, Good engine lower. I would of thought more vacuum under power.

I guess I have to get more cooler water into exhaust manifold a different way then I have now.
 
Okay, let me explain. The exhaust cooling water enters from the bottom and exits through the two rubber hoses into the large rubber hose that dumps the hot water released by the two thermostats. I have never experienced an exhaust overheat but I would begin by removing the two rubber hoses from the exhaust and check that with the lower unit removed, that water flows freely back down the exhaust aswell as though the small hoses to the dump pipe. I can't see any reason to try and modify anything, you need to systematically find the problem. If you are certain the exhaust is the issue I hope this bit of info helps
 
When I had the engine apart over the winter, I examined the exhaust manifold as well and reviewed how the water flows into it.
Last summer I found that routing those 2 rubber hoses at the top of the manifold directly out of the back of the engine improved cooling. (gets that hot water out/off engine rather that returning to large vent tube that combines the Cylinder/Block water flow through their associated thermostat). Currently have those 2 hoses neatly routed to rear of the engine and out.

I previously thought I addressed about everything associated to the cooling system, so figured look at Fuel/Air performance. However now appear by swapping parts between the 2 engines this area of concern appear is working as the good engine. So back to cooling, however I think I exhausted (no pund intended) every possible area.
 
All the temp sensors will cause engine shut down if there's an overheat issue. Try running the engine without thermostats. I have fixed persistant overheat issues on 225s by replacing thermostats with 50 deg ones. I have worked on these 150s since their inception and have never had an unsolvable overheat issue. It would also help to have Dr H to see exactly what is going on.Also, are you positive you have an overheat issue and not an oil pressure alert? This shut down is also consistant with thrust washer failure?
 
Although I tested which sensor causes shutdown last year. I isolated the sensor from the ECM and connected voltage divider to the ECM, with the normal sensor voltage known I changed resistance monitoring my A/D computer interface and simulated increasing temperatures on took each sensor. I would get an alarm but no shut down until testing the exhaust circuit. When exhaust temp reaches 200F the alarm is sounded and engine is shutdown. I do observe the water temp light and not the oil pressure.

Previously I thought the overheating was due to Cylinder or the Block and tried no thermostats and also making both 50C. No improvement.
Wish I could afford Dr H and the licensing. All I can do is count blinks with shorting stub.

I do get a BARO Code (although measure about 2vdc on both engines). Replaced with new and upon turning the key an alarm sounds. put back in the older one and same sequence but no alarm. Even swapped BARO between the 2 engines.

The test ride today had 2 variables (1) swapping BARO Sensors between engines (2) reinstalling the Water Pressure Relief valve. Was able to get up onto plane, monitor temperatures exhauat around 180F, trimmed motors and trim tabs got up to about 20mph. Slowed down, turned around proceeded back to dock Might of pushed it too hard (or did not retirm everybody) and had engine shut down and alarm. Turned off the key waited about 5min turned key back on but did not start engine. Monitored exhaust Temp to drop below 200F, started motor at idle allowed water pump to cool thing down. reengaged propellor but did not push it this time. (Also testing out the VTEC on the non overheating engine that does not engage, separate discussion).
 
okay, will pull them out without changing anything else


I guess I confused Dr h with BUDS2. See on Ebay a Dr. H Kit for about $150 although it lists a BF150 up to 2006. Mine are 2010's.
I suppose Honda did not make too many changes. Will likely go for it.
 
Okay before my test run I pulled out both thermostats (50C for the head 60C for the block). Did nothing else on this engine. Floored both engines and then cut back a bit, and shortly after it triggered the overheat alarm with engine shut down. Gave a time to cool down , restarted and proceeded more gently, but soon I seen the temp in the 170 then 180 then 190's and got shut down. So I put the thermostats back in.

With both engines up round 4K I was doing about 20mph the "good engine running around 5K, throttled it back a little to get about 12 gal/hr fuel rate. The Other engine I was keeping an eye on the temp and engaged VTEC for a period got the boost and noticed upon activation RPM peaked about 4800 and then dropped back. Was moving along pretty well. I also had my auxiliary water pump shooting water into the exhaust manifold. Sometimes I had to reduce RPM drop out VTEC mode, but still cruising along. I some point I must of had the VTEC on too long and the Temp spiked above 200F and engine shutdown.

Also not sure I mentioned, I installed an external Oil Cooler, that I have in the water. In attempt to cool case temp.
 
UPDATE for iang6766:

Routed the 2 small hoses at top of Exhaust Manifold directly out of the engine (cover off). Also routed separate hose from the top of the engine where the 2 thermostats are located. Took for test ride, got it up on plane, the sister engine with no problems was about 5K and the other 4500rpm (VTEC energized). Monitor temperatures and exhaust running between 160 and 170F. the Head/Block running in the 190 range. Could maintain a speed of about 204mph. Auxiliary pump not engaged.

Water exiting exhaust manifold port at front of engine was hot to the touch whereas the port to the stern was warm (Underway). Obviously, the hose connecting to Head/Block was really hot to the touch. Water flow from small tubes had even stream, the Head/Block hose had water moving but since hose is about 1 inch ID the exiting water does not fill the hose but appeared to have ample flow.

Conclusion: With Head/Block hose routed directly out of the engine has a significant improvement in heat dissipation.
 
Do you have ample flow through the dump point in the lower exhaust tube? You can test with garden hose to see how much back pressure there is. Like I said before, I have never experienced an issue this side of the cooling system
 
Okay I'll give it a check.

I received the Dr H kit, loaded S/W connected to engine and then nothing. Can run samples but nothing from engine. Further troubleshooting in the interface box, no power is getting from outboard to internal electronics (appears a component is missing). Sent message to seller but likely I'm on my owe with this puppy. Appears the Ebay version of Healtech diagnostic kit is a product of China (not OEM). Something else to figure out. :-(
 
Update Report for iang6766:

Water goes down the tube with no resistance (not running). There are times where the open tube not connected to engine at thermostats pushes out some water. Likely water from internal oil cooler.

Got the Dr H working (a missing diode in supply line from engine to internal circuitry).

The version I have supports 3 of the 4 ECT's ) 1,2,3. Assuming these are mapped to ECT1 - Case, ECT 2 - Block, ECT 3 - Exhaust
Running at idle 735 RPM Case 120F, Block 129F, Exhaust 91F
Rev'd up 1000 RPM Case 134F, Block 134F, Exhaust 93

We'll get it out and record an under-way profile, waiting on a longer USB cable.
 
Back
Top