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Yamaha outboard water cooling


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Juno has been nowhere for years, and as the engine hadn't even started for five years last year I took it off and took it for a good once over. The guy stripped it down, fixed and changed several bits (including the impeller) and tested it in a tank. All fine.

 

Trouble is, for one reason and another it's taken me a year to put the engine back on. Now it's on it starts first time, but only a dribble comes out of the tell-tale.

 

I haven't run the engine out of the water, it was stored correctly on it's side.

 

I also haven't run it for long enough to get hot, although I'm unsure how long that is - its run for 30 seconds or so, 3 or 4 times. I'm aware the tell-tale is just that, evidence that the cooling is working rather than being the cooling system itself, so it could be the tell-tale is blocked, but it might not be, it might be more serious. 

 

Any thoughts? 

Edited by magpie patrick
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Unless the engine was 'winterised' the lack of use for 12 months will (almost certainly) mean that the impellor has dry-welded itself to the pump housing. Running the engine will have torn off one of more impellor 'fingers' and you will be getting a much reduced flow - and - the possibility of bits of rubber being sucked further into the cooling system and blocking the waterways.

 

Its an easy enough job to check the impellor and replace if necessary.

 

For future reference, either store the engine in the water (so the pump is submerged and the impellor kept 'wet', or remove and keep the impellor in a jar of vegetable oil (or smeared in Vaseline) to stop it drying out.

 

There again - a spider could have camped out in the tell-tale...……………………...

Edited by Alan de Enfield
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First of all try poking the tell-tale with a piece of wire in case a lime scale has formed across part of it.

 

Some of the Mercurys on out day boats were a bit like that, so squired as expected and some did not a lot more than dribble. We only worried when they stopped completely and then often galleries cast into the base of the engine block were corroded up.

 

 

  • Greenie 1
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11 minutes ago, Tony Brooks said:

First of all try poking the tell-tale with a piece of wire in case a lime scale has formed across part of it.

I was going to suggest that, but having seen the problems it can cause I would suggest it is better to remove it from the engine before poking it.

Once removed from the engine, poke something softish down from the engine end to get any blockage removed.

 

If you want to poke it in-situ be very gentle.

You can push any blockage back up the tell-tale, or even pierce the rubber tube with a bit of wire.

 

 

 

Blocked tell-tales were a big problem on our clubs sea-going outboards but this was generally down to a build up of salt - it also showed what risk there was of salt blockage in the galleries. It was vital to use a muff-flush and hose after every trip.

 

 

 

Running in 'fresh water' should not be such a problem, but agree there is a possibility of limescale build up.

Edited by Alan de Enfield
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1 hour ago, Alan de Enfield said:

 

Its an easy enough job to check the impellor and replace if necessary.

 

 

Is it easy enough with the engine on the transom and the boat in the water - ten minutes standing in the canal is probably easier than lifting the damn thing off again! 

 

I'm guessing the lower unit needs to come off

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1 hour ago, Tony Brooks said:

First of all try poking the tell-tale with a piece of wire in case a lime scale has formed across part of it.

 

Some of the Mercurys on out day boats were a bit like that, so squired as expected and some did not a lot more than dribble. We only worried when they stopped completely and then often galleries cast into the base of the engine block were corroded up.

 

 

I always used a bit of strimmer line to clear the telltale - has worked for the last 40 years without damaging anything.

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11 minutes ago, magpie patrick said:

I'm guessing the lower unit needs to come off

Yes.

 

Easy enough on land but stood in the water and 'dropping' the whole lower leg and gearbox, then trying to re-align the splined  shaft back in is not going to be easy - even on full-tilt.

 

Can you get the backend up a slipway ? Or, onto a trailer ?

No need to take it off the transom but its not a great idea to try and do it in the water.

 

5 minutes ago, Chris G said:

I always used a bit of strimmer line to clear the telltale - has worked for the last 40 years without damaging anything.

Yes - ideal stuff.

Edited by Alan de Enfield
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14 minutes ago, Alan de Enfield said:

 

Can you get the backend up a slipway ? Or, onto a trailer ?

No need to take it off the transom but its not a great idea to try and do it in the water.

One thought I'd had was to book her in for anti-foul and do it then. There is a dry dock here about 400 yards away.

 

Otherwise it probably is get the engine off

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Just now, magpie patrick said:

One thought I'd had was to book her in for anti-foul and do it then. There is a dry dock here about 400 yards away.

 

Otherwise it probably is get the engine off

Try a GENTLE poke 1st but be prepared to switch it off quickly if it doesn't clear. 

 

What size engine is it ?

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1 hour ago, Alan de Enfield said:

Try a GENTLE poke 1st but be prepared to switch it off quickly if it doesn't clear. 

 

What size engine is it ?

9.9 long leg - weighs about 45 kilograms. I can get it in and off on my own but it is not a pleasure. 

 

The only significant journey its done on Juno was Crofton and back - about 80 mile round trip - in 2012, a few weeks later I was dangerously I'll and 18 months later I took the silly decision to buy a knackered narrow boat, hence the neglect until last year. 

 

Engine was bought second hand from someone who had used it a few times in the solent before opting for a bigger model. The paint on the outboard leg was undamaged when I got the engine. Unlike some it probably suffered from under use. 

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1 minute ago, Alan de Enfield said:

Is there a key-way in the shaft ? (is there a key in place ?)

Will the impellor turn without turning in the shaft ?

 The impellor certainly looks to be in good condition.

One the impeller won't turn without the shaft, or at least I can't get it to do so

 

I had wondered if the therefore the shaft isn't turning... 

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2 minutes ago, magpie patrick said:

One the impeller won't turn without the shaft, or at least I can't get it to do so

 

I had wondered if the therefore the shaft isn't turning... 

If you turn the prop, does the shaft turn ?

 

Slide the leg back together don't worry about reassembling the pump.

Pull the engine over on the cord (in gear) - does the prop turn ?

If someone tries to hold the prop and you pull the cord does the prop try to turn ?

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Put leg back on - prop turns freely independent of the engine. I am about to test but I'd say more freely than with the leg off so I don't think the prop is driving the shaft when the leg is on (which, in neutral it shouldn't be) 

1 minute ago, magpie patrick said:

Put leg back on - prop turns freely independent of the engine. I am about to test but I'd say more freely than with the leg off so I don't think the prop is driving the shaft when the leg is on (which, in neutral it shouldn't be) 

Correction - now I've taken the leg off again the prop no longer turns the shaft

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28 minutes ago, magpie patrick said:

Put leg back on - prop turns freely independent of the engine. I am about to test but I'd say more freely than with the leg off so I don't think the prop is driving the shaft when the leg is on (which, in neutral it shouldn't be) 

Correction - now I've taken the leg off again the prop no longer turns the shaft

It would appear then that the shaft is not engaged in the splines at either the 'top end', or, maybe, the 'bottom end'

 

I cannot really think of anything else 'at a distance diagnosis'.

 

Try and get the shaft re-orientated so it drops into the gearbox (splines engaged) and see if that reactivates the prop to shaft connection.

Try again replacing the leg and ensure that the shaft goes up into the splined receiving shaft (it is possible to 'miss' which is why I suggested it would not be easy to line up whilst still in the water)

Try again with the engine in gear (maybe you missed that bit in post #15)

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15 minutes ago, Alan de Enfield said:

 which is why I suggested it would not be easy to line up whilst still in the water)

I'm very grateful for all your advice Alan, but especially for the bit that said don't do this whilst standing in the canal!

 

I'll follow the suggestions and report back

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On 01/09/2019 at 16:35, Tony Brooks said:

I have known splines in the crankshaft to wear (more often its the spines on the shaft) and sometimes they only drive when they think they will. If you drop the leg again try to get a torch so you can look up into the end of the crankshaft.

I assume that the rod in the photo is the gear change actuator.  I know that on the big Yamahas (85hp) you need to put the gearbox into gear (and presumably the gear change lever in the same gear)  before you attempt to offer up the bottom end.  Can't anybody find a workshop manual online?

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