descaling a small outboard without dissembly

[Birdseye]

Problem - no water coming out of the telltale. Second problem - the engine is mid 90s, never been apart and my efforts to inspect the water impellor ( it was OK) yielded one sheered bolt head.

In an ideal world I would remove the cylinder head and clear out the water passages but 3 of the 4 bolts are really tight and I would be surprised if they didnt shear.

I could get some chemical in through the telltale hole but would it dissolve the internal crud. Any ideas?

 

[Graham376]

Telltale can usually be cleared with a bit of wire but I don't know what will dissolve salt crud without harming alloy. Brick cleaner containing muriatic/hydrochloric acid works OK on cast iron engines but I'm told shouldn't go anywhere near aluminium.

 

[VicS]

Problem - no water coming out of the telltale. Second problem - the engine is mid 90s, never been apart and my efforts to inspect the water impellor ( it was OK) yielded one sheered bolt head.

In an ideal world I would remove the cylinder head and clear out the water passages but 3 of the 4 bolts are really tight and I would be surprised if they didnt shear.

I could get some chemical in through the telltale hole but would it dissolve the internal crud. Any ideas?

Circulate Rydlyme. Provided there is some flow it should do it but a waste of time trying if it is completely blocked solid

 

[FairweatherDave]

You are right to fear shearing the bolts. However I have managed to drill out and fit larger bolts on two outboards so it is remediable. If you are lucky rydlyme might work but it didn't for me. I do a lot of outboarding in the shallows so it is not suprising my cooling got blocked. I am being a bit provocative but have you any evidence of overheating? Do you only do fairly short trips? Only a small percentage of cooling water goes out the teltale. Could you gamble and carry on? I'm not advocating this but I would also be pretty certain your bolts will shear.

 

[ShinyShoe]

strimmer 'wire' poked into the tell tale is considered safe to dislodge 'crud' stuck in the hole without damaging the internals of the cooling ducts.

If it is rock solid sea salt encrusted - thats not going to shift it. Hot water and rydlyme etc may help. But it needs to get in contact with the solids and if they go all the way through it will take an awful lot of flushes...

I am being a bit provocative but have you any evidence of overheating? Do you only do fairly short trips?

Are they critical trips? i.e. if your engine fails do you have the ability to row instead or are you not up to it / the tide etc too strong. If the engine fails where will you end up.

Only a small percentage of cooling water goes out the teltale. Could you gamble and carry on?

That does assume the rest is flowing. If it isn't you will overheat. If it is you loose the ability to track that its not... But if its just the telltale - you'll clear it with some poking and some cleaner...

 

[thinwater]

Circulate Rydlyme. Provided there is some flow it should do it but a waste of time trying if it is completely blocked solid

Rydlyme is inhibited HCl and is not very gentle on aluminum.

Practical Sailor did tests and showed that CLR (lactic acid) was about 4 times less damaging to aluminum for the same cleaning effect. Best Choice for outboards.

Ordinary, through, if it is really jammed up, you will need to get inside to rod out some passages.

 

[BobnLesley]

Telltale can usually be cleared with a bit of wire but I don't know what will dissolve salt crud without harming alloy. Brick cleaner containing muriatic/hydrochloric acid works OK on cast iron engines but I'm told shouldn't go anywhere near aluminium.

I'd heard/read the same thing, but having bought a new Nissan 3.5hp to replace a 17 year old old Mercury 3.3hp (both 2-stroke) whose major problem was barely a trickle of cooling water coming through, I tried pumping a muriatic/water mix through for ten minutes then flushed it with fresh, rather than just throwing it into the skip. It cleared the waterways a treat and the aluminium engine's seemed uncorncerned by the abuse, so for the last year or so we've had two outboards on the pushpit and actually, I still think the old Merc's the better of the two.

 

[SAMYL]

You really don't get much gunge out by just removing the head. Most small outboards come apart easily at the joint between the power head and the tube down to the prop end. Once apart there are several channels usually full of gunge and easily cleaned out.
I wouldn't even bother with the head, most of the blockages will be in the channels mentioned above.

 

[aquaplane]

I'm wondering if my impeller is getting old too. I could have restricted waterways but a tired impeller may give the same symptoms. And I have already sheared one of the bolts holding the bottom of the leg on when I tried to check my impeller, so I'm not touching the other one.

I'll try running some mild acid through to see if it improves the flow, I have a jar of citric acid somewhere.

 

[seaangler23]

Rig up a drip into the tell tale and fill it with coke, it’s worked for me a few times but depends what the build up is

 

[dragonvc]

I descale the house pipes with citric acid works well leaves copper clean ,do not leave for two long though.

 

[Spyro]

I'm wondering if my impeller is getting old too. I could have restricted waterways but a tired impeller may give the same symptoms. And I have already sheared one of the bolts holding the bottom of the leg on when I tried to check my impeller, so I'm not touching the other one.

I'll try running some mild acid through to see if it improves the flow, I have a jar of citric acid somewhere.

I had similar symptoms and it turned out the impeller was shredded. Two bolt sheared at the head but it still allowed the bottom of the leg to be separated with a bit of pressure. I managed to get a vice on to the section if bolt that was left and remove them. I just tapped out the existing hole and fitted new bolts

 

[MikeBz]

When this happened to my Suzuki DT2.2, despite regular flushing with fresh water, the little cooling channels in the head were blocked solid with what I assume was a mixture of limescale and silt. It was physically quite hard to dig it out with the head off, it couldn't have been done any other way. A year later it happened again, despite flushing on every return from the mooring.