Honda BF10 odd cooling issue

[Fire99]

As many will know, I have a Honda BF10 4-stroke as my boat engine. It's only 2 or 3 years old and to be honest, runs like a dream. (Lets put aside the sheer weight and lack of hand-holds for a minute)

Anyway, it's been in the boat's 'well' for the best part of a year and has got pretty fouled in that time. I took her off and put her in the cabin for a couple of weeks and scraped the barnacles off and cleaned the water inlets but I noticed when I motored the boat to come out of the water, there was greatly reduced teltale water coming out. (It's normally bordering on a jet of water)

Anyway, engine is home, Gearbox removed and there was a load of mud around the gearchange shaft etc. I've cleaned it all up, inspected the water pump impeller and it seems virtually brand new but there could of been plenty of mud in the inlet.

Anyway, reassembled, flushed hose down thermostat housing and then started her in a tank. Got significantly better water flow but not as good as it was earlier in the year.
Stopped engine, put covers back on etc. Restarted and the flow was minimal again.

Any thoughs gang?

 

[Courageous]

Did you remove the impellor for inspection? It is possible for the rotor to seperate from it's boss. It will still look good but the boss will be slipping inside. Just a thought.

 

[Silent Lady]

Outboard Engine

We have a Mariner Engine . Similar problem with water . Took the thermostat out and cleaned all the salt out . Replaced the impellor . Put hot water in to desolve the salt that was left . Much better than it was .

 

[Fire99]

Yeah I took the impeller out. It has a metal locating pin which slots into the impeller to locate it on a 'flat' on the shaft. All fine and dandy.

I may order another impeller to be on the safe side but I very much doubt that is the issue.

Some hot water through the thermostat may be worth a go to see if that helps.

thanks so far.

 

[VicS]

You may have shifted some mud further into the cooling system where is is now blocking things up.

Have you made sure the telltale itself is not blocked?

Does the engine have a flushing hose connection or is there a kit to fit a hose for flushing? If so it would perhaps be worth while flushing it through.

When you had the gearcase off did you connect a hose to the water tube to make sure it was all clear and flush it through. It might be worth dropping it off again to do that.

I'd put a new pump impeller .. not go to the trouble of stripping it down and then putting the old one back, although if only 2 or 3 years old it should be OK

 

[Fire99]

You may have shifted some mud further into the cooling system where is is now blocking things up.

Have you made sure the telltale itself is not blocked?

Does the engine have a flushing hose connection or is there a kit to fit a hose for flushing? If so it would perhaps be worth while flushing it through.

When you had the gearcase off did you connect a hose to the water tube to make sure it was all clear and flush it through. It might be worth dropping it off again to do that.

I'd put a new pump impeller .. not go to the trouble of stripping it down and then putting the old one back, although if only 2 or 3 years old it should be OK

Hi Vic,

Thanks for that. Yep i've poured warm water through the thermostat housing and it's pouring nicely out of the telltale.
I wouldn't be surprised if some salty mud has got sucked up into the heart of things. There was alot of mud in the leg above the gear case. Just goes to show, my bilge-keeler will happily take to the mud but sucking it up in the outboard is less advisable.

I've not sent water up the water tube yet but since the gearcase is still off, i'll do that shortly and yep i'll order a new impeller. May as well be careful and I can keep the old one for emergencies.

I've ordered the flush attachment that screws in above the thermostat housing so hopefully that 'll help things too.

One thing is for sure, it's alot more grief moving this thing around than my 2.5 2-stroke Mariner.

 

[VicS]

One thing is for sure, it's alot more grief moving this thing around than my 2.5 2-stroke Mariner.

Yep 42 kg for the standard shaft model ... and they get heavier as they get older.
I used to be able to carry my Evinrude but its too heavy now.

 

[Fire99]

Yep 42 kg for the standard shaft model ... and they get heavier as they get older.
I used to be able to carry my Evinrude but its too heavy now.

To be honest, it doesn't help that honda use curved covers made of light flexy plastic (ironically to save weight i'd guess. ) but because of that there are very few grab holds. 3 specific ones and that's your lot.

 

[William_H]

Yeah I took the impeller out. It has a metal locating pin which slots into the impeller to locate it on a 'flat' on the shaft. All fine and dandy.

I may order another impeller to be on the safe side but I very much doubt that is the issue.

Some hot water through the thermostat may be worth a go to see if that helps.

thanks so far.

If its anything like a Johnson and many other impellers there is a central metal boss which fits onto the shaft with a key. The problem is that the metal boss is bonded to the rubber of the impeller and this bond fails leaving the impeller not turning. The impeller can also wear on the sides as can the cover plate where the side of the impeller rubs. Good luck olewill

 

[VicS]

Yes very smooth shape aren't they. I get my shoulder under the back of my Evinrude and lift it like that onto the (lowered) bracket last thing before it goes down the slipway. The yard would do it for me .. and it may come to that in another couple of years

 

[Fire99]

If its anything like a Johnson and many other impellers there is a central metal boss which fits onto the shaft with a key. The problem is that the metal boss is bonded to the rubber of the impeller and this bond fails leaving the impeller not turning. The impeller can also wear on the sides as can the cover plate where the side of the impeller rubs. Good luck olewill

The honda appears to have a metal key that slots into the impeller and that mates up with the flat surface at the bottom of the shaft. It's certainly not bonded now though it doesn't appear it ever was, though I couldn't be certain.

 

[Fire99]

Yes very smooth shape aren't they. I get my shoulder under the back of my Evinrude and lift it like that onto the (lowered) bracket last thing before it goes down the slipway. The yard would do it for me .. and it may come to that in another couple of years

Yeah a right pain. Added to the fact it can only go down on one side, it's a slog. I like to think i'm a pretty strong chap but i may hang it off the tractor when I re-install it next year.

 

[Fire99]

Well shiver me timbers , the outcome of my water problem was infact the telltale being partially blocked. You could see down it, blow down it but when you connected the hose to it, variable results.

Ran without the Telltale connected (just the hose) and a nice flow of water. When the revs rise it feels like a power shower so all in all seems ok.

Just goes to show, sometimes it's something pretty minor. At least the engine is well flushed now.

 

[VicS]

Always the first thing to check ... but often overlooked.

I dont know the ins and outs of the Honda cooling system but it may not be advisable to actually run without the outlet nipple. Too much water coming out there could stave the engine of water.

 

[Fire99]

Always the first thing to check ... but often overlooked.

I dont know the ins and outs of the Honda cooling system but it may not be advisable to actually run without the outlet nipple. Too much water coming out there could stave the engine of water.

Yep, I overlooked it. I assumed (always the first mistake) that if I could see down it and blow down it then water would escape. Alas no.

Anyway, all clean and reconnected and a pretty good stream of water. It's a fair ol degree of pressure once the revs rise.
Also i've found that the outlet nipple for draining the carb is identical and adjacent to the water telltale so if it goes pearshaped you can just switch the pipes over.

Only negetive i'd say is the hose between the engine outlet and the nipple could be a bit tougher. Where it bends, it collapses a bit too easily for my liking so I may replace that.

Rather alot of flaff but atleast I have a better understanding how this engine works which is good when you're relying on it at sea.