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BF30 overheat warning

J

Jakey555

New member
I recently have been using and evaluating a Honda BF30D from 2010.
It was bought with 'suspected' overheating problems.
I've been out with it three times with no overheating, one with lots of WOT running. I was about to conclude that it had no issues at all, as it's also been moved down half an inch on the transom and is sucking water better than it was. It also had a wiring fault (now fixed- thanks Mike) that was causing it to run on- which I had optimisticallly told myself had been wrongly diagnosed as overheating related dieseling.
However, the fourth outing after warming up then running for about 3 minutes at WOT the overheat buzzer sounded and it shut down seconds later.
Lifting the cowl straight away, it really didn't feel particularly hot. It was comfortably touchable everywhere I could reach on the block and head. The crankshaft and flywheel had got hotter, but not too hot to touch. The flywheel bolt was totally undone... not even finger tight due perhaps to heat expansion losening it? I tightened it back up with my fingers.
I started it up again a couple of minutes later. It hardly ran, and was making a metal on metal grinding noise, but the teltale was squirting well, so I switched it off and got a tow home.
Looking at it again on shore I realised the flywheel was slipping and the whitworth key that keeps it from slipping on the crankshaft had been worn away. I guess this explains the metal on metal noise and how it hardly ran (the timing must have been more than a little out). How on earth it started is a mystery to me though! I guess the starter engaging must have been tilting the flywheel on the tapered shaft so it gripped it a bit. Temporarily I have wedged a sliver of steel plate behind the worn down whitworth key so now the engine runs- and it sounds fine albeit on the drive with muffs. Compression is good and the oil smells fine and is not emulsified.

I checked the thermostat in the kettle and it seems to be opening fine.
The waterways I can see from removing the plate behind the thermostat and the thermostat housing are very clean- no corrosion/ salt.
It squirts water at very high pressure from the teltale.
But at noticably lower pressure when I run it with the thermostat out.

I suspect an obstruction that is floating around in my waterways causing an occasional and isolated blockage. Somthing small enough to get in but too big to get out- a stray impeller vane perhaps from a previous impeller failure? I'm thinking it didn't feel hot where I put my hands but may have an isolated hotspot somewhere that I didn't find perhaps due to a single blocked gallery.

I won't have to go far to get a beat up but good runner BF25, which I could cannibalise for its powerhead then swap over the carbs, cam, CDI, but I'd like to have more of a go at fixing this one first as the fact that I've used it three times with no problems suggest that its issues may be only marginal. I could possibly just get away with running it with no thermostat, but how long would it take to die?

What's my next stage? Are there any further parts of the cooling system that can be checked without taking the powerhead off. and not requiring special Honda tools?
I know that some engines have a bit of a trap design behind a relatively easy to remove plate close to where the cooling water comes in up the pipe from the impeller, in an effort to catch some bits of impeller, salt and crud before they go too deep into the water galleries.
I'm guessing if I have to split the head and block to look in the water galleries there I won't get away with reusing the head gasket?
 
EEEEEEEEEEW! SCREECHING METAL SOUNDS! My teeth HURT! ;~)
Whitworth key....hmmmm. I wonder if he was related to the Woodruff key I grew up with?

Anyway,
I'm wondering if your overheat issues ARE related to the timing getting out of whack due to the loose flywheel? If she goes LEAN (timing WAY advanced) for just a little bit under load...she would get hot RIGHT NOW QUICK.

I would think that anything that could work it's way up into the water jackets should "reverse flush" back out if you keep at it. You will likely need to remove the gear case and pump to get the water tube off and expose the inlet to the block. Inspect there THOROUGHLY and do a little "soft" probing with a wire.

Then...using whatever you can put to good use....rags....rubber sink stopper....WHATEVER....fashion a seal for the inside of the TSTAT housing for your hose and FLUSH FLUSH FLUSH. Maybe even some compressed air to see if you can get anything to come out.

I've seen those nuts get loose too and Honda makes the crankshaft SO HARD that a new nut, key and thrust washer put 'em all back in business. I now listen for the tell tale "PING A DING A RING A LING DING" sound every time I run one JUST for that very reason. If I hear the little bells going off on a Honda....I IMMEDIATELY check that nut.

Good luck.
 
Re:
You will likely need to remove the gear case and pump to get the water tube off and expose the inlet to the block. Inspect there THOROUGHLY and do a little "soft" probing with a wire.

Then...using whatever you can put to good use....rags....rubber sink stopper....WHATEVER....fashion a seal for the inside of the TSTAT housing for your hose and FLUSH FLUSH FLUSH. Maybe even some compressed air to see if you can get anything to come out.

This sounds like excellent advice... well within the abilities even of somebody who does not know the difference between his Whitworths and his Woodruffs!
It also combines all the things I like best about boat maintenance on a budget. It's free to do, involves making something, invloves using the air compressor, and if it works I might get the intense satisfaction of seeing the offending blockage drop out.
I wonder if I might purchase a second thermostat housing from an engine breaker for a reasonable sum- then I can thread in a proper water fitting and bolt that f111cker straight back onto the motor and connect up to my pressure washer with no leaks...

There was definitely no thrust washer. I would have heard it go plop when I took the cowl off, and it's not sitting down in the undertray either. I've put one on now.
 
I should be more careful with my replies....I was speaking generically about MOUNTING washers... and misspoke. And...it seems YOUR outboard doesn't even have one of those.

Whitworth...Woodruff....It doesn't matter...as long as we understand each other.....

.....anyway...I like Whitworth BETTER! It sounds...well...PROPER!

Also...don't be surprised if NOTHING comes out. Although if this is a saltwater engine....a heavy dose of SALT AWAY or WHITE VINEGAR OR BOTH....might produces some white "powder". And, your overheat could have been because of a timing issue due to the loose flywheel.

And, while I don't think hooking in your pressure washer would do any damage....I would NOT go 1100 psi + with it. You don't need it and that sort of pressure can cause "erosion" of gasket material and maybe even aluminum casting. And, if there IS a plug in there somewhere...the thing that goes POP...might not be the thing you wanted to got POP. If it won't dislodge with 100 psi...then it probably needs to be MECHANICALLY retrieved. And...if that doesn't work...it could be dissolved in an engine cleaning bath while everything is apart. But...then again...she is your property and YOU can try anything your heart desires.

Just sayin'

Good luck.
 
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Finally got round to back flushing this last week.
I did it with an old rule 500 GPH bilge pump and a fairly weak acid descaler designed for household central heating systems (phosphamic acid). I also placed the pan that the acid was collecting in under the motor on top of an old camping stove so I was circulating hot acid. Periodically getting the airline blowing down the telltale tube seemed to help it dislodge more.
Lots of bits of shredded black rubber came out although the impeller that is on it is new and undamaged, so the bits aren't off this one. Plenty of white scale came out too. I needed two lots of acid (this stuff has a ph indicator in it so it changes from yellow to green once it's been neutralised and is no longer working) after the acid I backflushed and forward flushed with lots of fresh water as I'm sure boiler descaler is not a good idea to leave in the motor long term.
Anyway I've had the boat out twice since and it's running like a dream now and not getting hot.
Many thanks.
 
Way to GO!

Phosphamic acid.... R-NH-PO3H2.....One of the three types of HIGH ENERGY PHOSPHATES. The other two are: PHOSPHOPHOSPHORIC and PHOSPHOSULPHURIC......who knew?

Well...I didn't ....I looked it up.

Pretty clever and....since the "agent" seems to be closely related to TIDE detergent....probably not TOO harsh.

Although I did wonder about how your Rule pump was liking having to move that hot acid :~)

Glad you got it and thanks for the update.

Question: Where did you purchase the "descaler"?
 
I used Fernox Ds3.
I saw it described somewhere online as Phosphamic acid, but looking at the safety data sheet for it, it is described as Sulphamidic acid.
Looking at both these acids though, they are both sold for household heating system descaling purposes so may be quite similar.
I didn't just chance it. It's discussed on other forums as a viable outboard motor chemical flush.
I also learnt that if you have tried everything else and your powerhead is otherwise scrap, you can use brick acid (HCL). But, it's seriously noxious to use and will eat corroded and unpainted aluminium just as fast as it eats salt and other unwanted deposits. It wasn't worth the risk for my relatively new engine, but I've had motors before where I've tried everything so worth bearing in mind to get a final extra season out of a complete scrapper.

The bilge pump was an old one I had in a spares box and I was expecting it to expire, but it's all plastic apart from the stainless steel shaft (which is now badly tarnished), so has survived well. The stainless steel kitchen spoon I stirred the acid with is also now black. The pump started laboring at one point when the acid got particularly hot, so I had to turn the cooker down a bit at that point. It also ran for 2 hours or so in total with only short breaks to refill the acid and adjust pipework so I have a new found faith in Rule bilgepumps.

I have a cheap drill powered rotary pump, but could not find it so used the bilge pump. The next day, the cheap drill powered pump turned up! This would be my preferred pump as it was about £5 off ebay, only has very few parts and can be totally dismantled for cleaning once the job is finished. I would have used it in an old drill though as 2 hours is a long time for any drill motor.
 
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