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BF40A-ONGOING OVERHEAT ISSUES

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OLD DOG 4 NEW TRICKS

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DOES A 1997 BF40A HAVE A RELIEF / POPPET VALVE?............ I ORDERED THE SELOC HONDA REPAIR MANUEL AND IT CAME TODAY, BUTI I HAVE NOT YET FOUND THIS INFO AND I'IVE REPLACED MOST EVERYTHING ELSE (T-STAT,IMPELLER KIT WATER JACKET...) ON THIS USED MOTOR INCLUDING THE HEAD GASKET THIS WEEK. IT'S BACK TOGETHER, IT STARTED RIGHT UP, IDLES FINE, (IN 20 GAL TUB ABOVE PLATE) BUT IF I INCREASE THE RPM TO ~2K-3K THE OVERHEAT BUZZER COMES ON. I'VE BEEN READING BITS AND PCS. HERE FOR A COUPLE SUMMERS NOW. FINALLY GOT MYSELF REGISTERED JUST NOW AND HOPING FOR FURTHER GUIDENCE. EACH TIME I OPENED SOMETHING I FOUND DEBRIS IE. SM PCS OF PREVIOUS IMPELLER, SAND AND MORE SAND, HAVE REMOVED AND CLEANED PEEPORT A DZ. TIMES (SOMEWHERE I SAW REFERENCE TO AN UPGRADED / LARGER DIAMETER BRASS PEE PORT OUTLET, BUT HAVEN'T LOCATED IT AGAIN )...THANKS,... IDEAS? LAUGHS? OLD DOG TRYING TO LEARN NEW TRICKS
 
Is there any tell-tail stream at all? Is the motor noticeably hot, have you felt the motor or used an IR temp gun to confirm it's actually overheating?
 
Good morning, thx, yes there is a good stream from the telltale. The motor does feel hot, at least to my senses. I did buy a cheap ir gun yesterday , As I tried to figure exactly WHERE to pinpoint temps, I found intake ~ 130=165? t-stat housing went ~160 up to 200+, head seamed to vary, ~140-150 low, w160-180 mid and 170-200 top#1 as I increased rpm from ~800 idle-2500. I did not stop and write down exact #s. The sputtering exhaust water from the mid lower end seemed to turn to steam, but the alarm did not go off this time(?) I recall some temp expectation from a prev. thread ref. 158 degrees?.................then it got late ..............I recall several references to a relief valve that is supposed to open at higher rpms, but I don't think this '97 bf40 has that. then I wondered about the oil pump and pressure. Is there a way to check the oil pressure?
 
Hi,
Welcome to the forum.
Sorry you're having problems.

I am no Honda 40 hp guru, just so's you know.

You're probably not going to like what I have to say but you need help so I'll say it anyway.

It does sound like she's still getting hot or what I.call "localized temperature spikes" within the engine.

Based on your description of the junk you've already removed I believe there's probably plenty more in there.

It has nothing to do with the tell tale either. The tell tale does little to nothing to help cool the engine. It is an "information only" circuit to show that the pump is moving water. So, even if it were completely plugged, it would not be the cause of overheat/poor cooling. You say you have a good stream as is so your pump is, well, pumping and the engine shouldn't be overheating or alarming.

I think you are correct that this model has no "relief valve".

What I have seen here over time is the engine blocks get "mineralized" and "stuff" gets trapped in the cooling passages.

The guys that post up about this and report the most success in clearing/cleaning the system report using mild chemicals such as Rydlyme, CLR and/or good old vinegar in a trashcan mixed with water.

Some guys run the engine to circulate the mixture while others have gotten very creative.

Running the engine in a trashcan in a cleaning solution creates a situation where the solution level and temperature must be closely monitored since no fresh, cool, make-up water can be added. As a result, when the water temp gets too high, the engine must be stopped and the solution allowed to cool.

One that impressed me most was a guy that, after repeated failures flushing, rigged up a pump that he could push the solution directly into the water tube with the gearcase removed. He devised a way to heat the solution while circulating it through the engine for hours this way.

He told of having great success with this method. Getting plenty of scale and debris out of his engine and resulting in a "fix".

If I can find his thread here, I will post it up for you.
 
"It has nothing to do with the tell tale either. The tell tale does little to nothing to help cool the engine. It is an "information only" circuit to show that the pump is moving water. So, even if it were completely plugged, it would not be the cause of overheat/poor cooling. You say you have a good stream as is so your pump is, well, pumping and the engine shouldn't be overheating or alarming."

Now that's some very confusing information regarding the tell-tail. Let me clarify for those who may require some clarification...
The tell-tail provides visual confirmation that the water pump is circulating water through the motors cooling system. Cooling System! This is exactly what it sounds like, so I won't beat that to death. When we refer to the tell-tail in a troubleshooting context it's the primary indicator for how well the cooling system is functioning in general. We are not focused on the tell-tail as a device or component that is coating the cowling and surrounding atmosphere with magick cooling water and steam. No, but we do get anxious when it's pristine fountain runs dry, this requires our attention to troubleshoot the issue focusing on the cooling systems components, not calling the dealer to order a new tell-tail streaming device and indicator gasket.
People do a huge disservice to the uninformed novice boaters looking for helpful advice when they say things like:

"It has nothing to do with the tell tale either. The tell tale does little to nothing to help cool the engine."

This is misleading and just bad information.
 
Read all of JGMO’s posts , he is very knowledgeable and tries to help, he doesn’t post bad information. If he is guessing something while trying to help, he says so. Guess why the telltale is called that, it tells a tale, it provides information only.
 
@siluetae137 , JGMO has a ton of experience with these engines. I think you misunderstood his point. Of course the tell tale functioning lets you know the water pump is working. The water pump can also be working with no tell tale if the small line gets blocked with salt crystals or other debris as often occurs with my BF 200. His point is that a functioning tell tale does not indicate the entire cooling system is working. Further, the localized temp spikes could indicate that some of the cooling galleries are gummed up with salt/minerals/debris. With a motor this old that may or may note have been frequently flushed, it is likely that some sort of chemical cleaning program like JGMO suggests could be just the ticket.
 
Well NSDON thank you for the support.

But I think siluetae137 is trying point out that putting it the way I did could confuse some people and I think he's (she's?) probably right.

While it IS true that the tell tale bypass water circuit does nothing to enhance engine cooling in any way, it still IS a part of the system.

I should have said something like "if the water pump is working properly, then the engine should not be overheating regardless of if the tell tale is plugged or not"

I don't know if that satisfies the complaint or not and I certainly don't get it right or explain it clearly every time.

What I was trying to do was get the OP to stop worrying about the oversized tell tale fitting he was looking for because THAT is not the solution to his problem.

The truth is, if a tell tale plugs completely, it will allow MORE COOL water to enter the engine instead of being pissed out the side of the cowl.

But I get his complaint because
I too rely on my tell tale to inform me about whether or not there is FLOW from the pump.

Lastly, I've seen many instances
where an outboard is overheating but the tell tale looks just fine. The owner is then perplexed because he sees the the good tell tale flow..But when I open up the pump, there's only 1 or 2 impeller vanes still intact.

The moral of the story is that, even when the tell-tale indicates that there is flow it is not to be completely relied on to keep pushing if your engine is telling you something different.
 
I read them and never doubted his skill and knowledge about boating/motors. Most of what JGMO advised was inline with what any of us would suggest and be in agreement with. It was only in reference to a few power statements that could be misinterpreted or send the wrong message to naive, beginner boaters with impressionable minds. As a young boater the thing that worried me most was for that outboard to stop pissing, and it's fear that motivated me to go above and beyond to prevent this from happening - including talking to mechanics, friends, researching every preventative measure and maintenance tip like winterization that I could find..had to figure out why this stream of water is so damn important. I sailed the entire season last year with what was presumably a clogged cooling system on my kicker motor because I knew it was manageable. The younger Mike would have closed shop immediately till it was 100% fixed. I slowly grew confident, became more knowledgeable, as we all do, still probably a bit more cavalier than I should when not single-handing, most of that badmotorpissing fear was shed and what little that's left is stowed someplace...hidden from the brutish and creepy side of reality.
 
jgmo said:
Well NSDON thank you for the support.

But I think siluetae137 is trying point out that putting it the way I did could confuse some people and I think he's (she's?) probably right.

While it IS true that the tell tale bypass water circuit does nothing to enhance engine cooling in any way, it still IS a part of the system.

I should have said something like "if the water pump is working properly, then the engine should not be overheating regardless of if the tell tale is plugged or not"

I don't know if that satisfies the complaint or not and I certainly don't get it right or explain it clearly every time.

What I was trying to do was get the OP to stop worrying about the oversized tell tale fitting he was looking for because THAT is not the solution to his problem.

The truth is, if a tell tale plugs completely, it will allow MORE COOL water to enter the engine instead of being pissed out the side of the cowl.

But I get his complaint because
I too rely on my tell tale to inform me about whether or not there is FLOW from the pump.

Lastly, I've seen many instances
where an outboard is overheating but the tell tale looks just fine. The owner is then perplexed because he sees the the good tell tale flow..But when I open up the pump, there's only 1 or 2 impeller vanes still intact.

The moral of the story is that, even when the tell-tale indicates that there is flow it is not to be completely relied on to keep pushing if your engine is telling you something different.
Click to expand...
Yep, so very, very true.

Hey, It's all good JGMO, I knew what you meant, and should have stayed the high road, my delivery wasn't exactly subtle, so that's on me too my friend.

Mike
 
Thank you all, .I DID find a lot more sandy debris and 2 sm pcs. of impeller (from prev. owner's paid repair just before I bought boat)) when I took the head off and replaced the head gasket. Since I had done most everything else I concluded that it may have a blowen head gasket allowing the exhaust gases into the water cooling passages and displacing that cooling effect. I only found the smallest of break in the center of #2 head gasket, while finding a couple tablespoons of sandy debris blocking ~80%? of the lowest water passage, I cleaned those out best I knew and blew compressed air ~90-100# pressure through all the openings. This seemed to work. After I reassembled, I ran in bucket with SIMPLE GREEN mixture (as I had last year) to hopefully clear out any remaining build-up from further within. I don't yet see any sand / debris in the tub but will drain, check and refill with clear water today. note in review, it would have been more precautionary to run cold water into the bucket while flushing to maintain a lower water intake temperature, but didn't want to dilute the SIMPLE GREEN mix further at that point to maintain it's effectiveness. It did get warmer than I had realized after increasing rpm.. will retest today.........THANKS............DOES ANYONE THINK A LOW OIL PRESSURE WOULD BE A FACTOR? When IS the RED oil indicator light supposed to be on, and when off? Does the low oil pressure alarm sound the same as the overheat alarm? My overheat is a steady buzz...................Thanks, OLD DOG.........
 
I can't answer the warning system question but you can check the oil pressure by removing the oil sender and temporarily attaching a pressure gauge in that port.

I think you will probably need a British.Pipe Thread (BPT) to National Pipe Thread (NPT) adapter....available on Amazon.....to make the connection.
At least that's how it is on my BFD 20.

Good luck.
 
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