Logo

BF150 Bucking Down w/ Alarm Sounding Above 4500rpm

BlueCrabRhodes

New member
I'm new to this forum thing...hoping for some help since I can't get any servicing dealers to return my calls.

Motor runs strong and perfectly until the rpm's increase to a point where the alarm sounds and the motor bogs down. If I do nothing, it bucks pretty harshly and ultimately shuts off. If I throttle down, the bucking is less harsh but always eventually shuts off. When I throttle down and turn the ignition off, it always restarts immediately. In regards to the rpm level for the issue to occur, when it's just me and Boomer it is right around 4500rpm...will run all day wonderfully at 4400rpm. With heavier load in the boat, the issue occurs at lower rpm levels, which is perfectly understandable. However, wouldn't this point to a fuel flow issue?

Some backstory; launched the boat in late April and this same issue occurred at only 1200rpm...would run fine at 1000rpm. My limited mechanical knowledge allowed me to think this was an easy overheat problem so I replaced the impeller. Ran the boat on a hose at 2500rpm for approx 20 mins and thought I was in the clear but then it happened again. Noticed some water in the filter under the cowling so I figured that was the issue. Changed all the filters, have gone through about 120gals of fuel while maintaining drainage of Racor and adding fuel treatments.

Now, it happens so predictably that I can't believe it's a fuel issue but a flow issue. Or are they the same?

I'm the guy that normally hires people for this stuff but fate has me unemployed this summer...great opportunity to go boating....if only the boat ran properly...

thanks for for any help...
Chris
 
To help you determine what the alarm is....there should be four warning lights.

Which lights are on and which lights are off?

Describe the alarm sound.....is it continuous or does it go on and off?
If on and off, is it at 1 second intervals or is it faster?

Mike
 
Mike...boat performed unusually poorly today. Would not stay up without bogging down, even at 4000rpm.

Oil level is good. Filter info wasn't visible so I looked up spec in past invoices from marina; 15400-PLM-A01-PE. Hoping that info means something to you.

When end the alarm sounds, it is a constant tone.

The lights that illuminate are the two on the left of the attached photo.

image.jpeg
 
If I am seeing it correctly...you indicated that the red and the green on to its right are both on.

The green light being on, indicates that the oil pressure is good.

The red light and solid alarm indicates that there is an overheat.

Normally, this is caused by bad impeller, stuck thermostat/s (there are two - and they are different from one another...so it matters where they go), blocked cooling passage or any combination of the above.

Sounds like the lower unit needs to be dropped and the impeller checked (might as well replace it while you are there....replace the entire pump, if in doubt).

Pull the thermostats at the same time and use a garden hose to backflush from the thermostat openings through the whole system. Make sure water flows out everywhere it is supposed to go in.

Mike
 
Overheat was my original thought, as well, so the water pump was changed out earlier this spring when the issue first started. Unfortunately, that didn't fix the issue.

As as for the thermostats, can they be accessed while the boat is in the water? It's in a slip and I have no trailer.
 
The thermostats are right on top of the motor. You should be able to get to them easily by tilting up your motor. Check them for any buildup of salt or other debris that could be partially blocking the water passage. http://www.boats.net/parts/search/H...6/BF150A6 XA/CHAIN CASE THERMOSTAT/parts.html

Remember not to mix them up.

Once you take them out you can put the cover back on and run the engine without them as a test and see if you overheat (since it happens rather quickly).

It is not good to run the engine any length of time without the thermostats, since the engine needs to get to operating temperature to operate correctly.

If the engine does not overheat, then replace both thermostats.

If it still overheats, once back at the dock, take the thermostat cover back off and start the engine. The water should flow good out of the openings. If you put the engine in throttle only and give it some throttle, it should shoot out like a hose.

Your engine is going to get wet doing this, so make your test very short.

If the water does not flow very well, then you are back to the impeller.

If that is the case, it would probably be best to change the complete pump with housing. It is somewhat expensive, but that way you can remove all doubt.

If all those tests indicate that the water pump and thermostats are good....that would address how the water gets into the motor. There could be blockage getting the water out.

There is a bypass that helps dump the extra water pumped at higher speeds. If it is plugged with salt or debris, that can cause an overheat. Part #15 http://www.boats.net/parts/search/Honda/Outboard Engine/2006/BF150A6 XA/MOUNT CASE/parts.html

There is always a possibility that a sensor or ECM can be bad, but you need to check the basics first unless you have the computer software to do the testing.

Hope that gives you a few things to check.

Mike
 
This is great info and I understand 99% of it but I have a couple questions before I get into taking stuff apart...

1) if I remove the t'stats and run the boat without them, how will I tell if the engine overheats? I guess the alarm will still sound? Don't the stats sense this and articulate to the alarms?

2) if the impeller was replaced earlier this season, is it possible that my "mechanic" missed a damaged housing when switching out the impeller only? I know it's possible, but how would it rank on a scale of competency?

3) where does that bypass (part #15) exit the engine? Can I see it while underway? If I was up to speed and could see whether or not it was flowing, would that be beneficial?

please forgive my elementary questions....I'm not a very mechanical person...
 
The thermostats are there to allow the engine to come up to the temperature of the thermostats....at that point, they open up and allow water to flow out of the engine.

If you remove them and it overheats, the alarm will sound as it has...it might take a little longer.

You can not see the bypass flow....you would have to disassemble them to see what they look like. That is why I put it down on the list.

Anything can happen when replacing an impeller. Things slip and do not go back together correctly. It could be possible that he only partially got the water tube into the opening on the pump. Lower unit would have to come off to check.....again, that is why I suggested starting and running the engine at the dock with the thermostat covers off to see what flow there is.

In fact, you might want to do that first to save a trip out to test if the flow is bad. That flow should be pretty solid and should look like a fountain when you rev the engine. Remember, just do this a short time for testing purposes....things will get wet.

Mike
 
Got it! Mike, thanks so much for this help.

I may may wait until Monday to do this testing. As long as I have the ability to boat on weekdays, I find it hard to go out on weekends!
 
Mike i hear you.
I have done exacting what you have described here to great effect. But as one who thru experience has tried the 'open thermostat housing' operation I recommend wrapping the lower part in a cut up bin liner with el tape to deflect most of the water. If The amount of water spewed out of everything is good then there is water everywhere & before too long we are looking for a connection/ el problem. Not dissing Honda Mike but a adition to his always sound advice.
 
Thanks for the input, Denmark Dean! Do you guys wear those wooden clogs while boating? Seems unsafe to me! ;)

I was thinking about having someone on hand with a leaf blower to blow the fountain water away from the engine...and to dry off the unit after the test. Whadiya think?
 
Do it your own way mate. Only trying to help, as we all do. Yes we have clogs while you have guns. Go figure.
 
Good idea, Deanmk! Especially good in salt water. We are in fresh water here so I have not had a problem with a short shot of water.


Mike
 
image.jpegimage.jpeg

Mike....my situation appears different than the parts page you sent me. There doesn't appear to be two thermostats. Is that square post in the bottom of the left chamber a thermostat? I didn't try removing it and I haven't run the boat yet. Also, there is some dirt and grit in the chambers but doesn't look like anything that stop water from flowing. Advice?
 
There are supposed to be thermostats in those openings. Next question would be who took them out and why did they leave them out?

At least you know the thermostats are not stuck closed.

Stand up for the puppy up and see if any water comes out.

We can address the thermostat's once we get some water flowing.

Mike
 
I bought the boat used from Rehoboth Beach, Delaware....which is a very salty locale. I'm thinking the dealer took the stats out because they were constantly getting stuck closed due to salt and sand.

"Stand up for the puppy up"? Seriously? I'm sorry, I need some help with that...
 
Denmark Dean freaked me out with the electrical short karma. I may have an actual mechanic at a nearby marina on my side. This is all beyond me and I'm starting to feel guilty about taking up so much of your time, Mike. You really have been awesome and I seriously appreciate it. Can I ask you to comment on what my potential mechanic has to say, when the time comes?
 
You can always ask.....lol

Some old folks do puzzles for relaxation.

This old "folk" gets on this forum.

Go figure!

If for some reason, I don't answer, I am sure someone else will jump in. This thread has had 150 views...so someone else is "watching".

Let us know how it comes out.

Mike
 
Thanks, Mike. Wow! This sure sounds like what I've got going on. My mechanic has gone MIA since Tuesday so I may be left trying to do this myself. Any chance you can send me the correct schematic so I know I'm at least working from the correct prints?
 
If you are going to get into taking off lower unit, midsection, and water tube....and....you have not done anything like this before....I highly recommend that you purchase the official Honda Repair Manual for your engine. It is not cheap, but will step you through what needs to be taken off and in what order. It also provides the torque values for putting it back together. https://www.amazon.com/Honda-Marine...ms&ie=UTF8&qid=1469237161&sr=1-1&keywords=150

Do the other tests before jumping into changing the water tube grommet.

It is not difficult to do, but it helps to have some step by step.

To get to the water tube grommet....remove lower unit......remove midsection (this involves removing the bottom motor mount)......http://www.boats.net/parts/search/Honda/Outboard Engine/2006/BF150A6 XCA/EXTENSION CASE/parts.html

That will put you to the bottom of the oil pan. The water tube and grommet are easy to remove at that point....just one small bolt and holder. Part #6 is the grommet http://www.boats.net/parts/search/Honda/Outboard Engine/2006/BF150A6 XCA/OIL PAN/parts.html
http://www.boats.net/parts/search/H...50A6 XCA/WATER PUMP VERTICAL SHAFT/parts.html
#7 is the water tube

Mike
 
Hey Hondadude! You still out there??

Mike, my mechanic and I are still working through this issue and perhaps it just got worse. We have replaced all the t'stats and sensors and the boat performs better but still bogs down at 5k rpm. We did examine the tube in the lower unit that was described in a different thread and found no issue around that grommet.

After replacing the lower unit, the engine developed a shimmy at idle after warming...seems to be missing...so we replaced all the plugs and found some evidence of moisture around the plug in cylinder 3. This morning, we are removing and cleaning all the plugs and removing the t'stats that we put in earlier (you may remember there were no t'stats in it at all when I started this). We will then recheck for moisture.

Ive made a call to the Honda dealer to see if they will rent the "Dr H" device so we can code the computer. We'll see what they say....I'm not hopeful.

Any insight? Btw, I hope you are well...
 
Back
Top