One of my AD31s has boiled!

[mickyb]

Hi all

Took my new (second hand) sealine out for a razz yesterday.

Before that though, I sent my brother into the dock to change one of her trim tab motors that had leaked through its bellow and gone goosed (oh thats going to cost me some pints - he managed to fit the new thingy but came out looking colder than something birds eye would produce!). Anyway, after he had warmed up, the tide was up and the lock gate opened. So "bring in the fenders" I barked... "lets take her to sea". I just wanted to see if having working trim tabs made a difference to her performance.

Off we went, into the river wyre estuary (lancs). Up and down the river we charged, then off to the end of the channel, then back up the river, it was great! it rained harder than ive ever seen rain before but who cares! We were alive! it was bliss..! For a good hour and a half I was at full chat most of the time and she behaved wonderfully! (still blowing some black smoke, and a bit down on revs but 23 kts was achieved when it was flat).

So with a big smile I declared "sea trials are complete, the suns over the yardarm" It was time for the pub.. so I backed the power off, called up the marina and got permission to enter the dock. As we were chugging up the dock channel at about 5kts, to my horror the temp warning light on the starboard engine came on, so I shut down the engine and limped in on one.. Now, im rubbish at parking her even with two engines available, so now only having the one engine, well i think I would have more chance of getting her on her berth by going below, kneeling and praying that the wind would blow her there all by itself! So to save upsetting all the nice people at my new marina and prevent all the insurance claims against me, i had to restart the hot engine which frightened me very much as it seemed to get hotter still! and the alarm went off.

As soon as I reached the pontoon I killed the engines and looked in the engine bay. The bilge had green antifreeze coloured water sloshing round so obviously the water had boiled out (as to be expected). Next thing I did was check the strainer filters - clean. Then I checked the impeller - it was fine. after it cooled a bit I restarted the engine. It started no problem, ran it and released the strainer cap a little - loads of sea water going through so it definitely isnt the raw water side.. so guess its now time to look at the fresh water side..

Sorry to give you such a long story (hope you enjoyed it though ) my real three questions are as follows..

1. Why did it do it when I eased off the power? - it was fine at full power. Someone I asked said it could be that the engine was heat soaked and by reducing the revs you reduce the cooling and the heat could remain in the engine could make it boil (dont really understand that one)

2. Whats the chances ive damaged the engine (C H Gasket etc) and is there an easy way to check?

3. Wheres the first place I should investigate on the fresh water side? are there any common things that could cause this?

I hate boats...

Thanks in advance for helping someone who's, well "nautically challenged"
M

 

[Kawasaki]

Hi all

Took my new (second hand) sealine out for a razz yesterday.

Thats good.


so guess its now time to look at the fresh water side..

Yep, it seems so

Sorry to give you such a long story (hope you enjoyed it though ) my real three questions are as follows..


Yes but such a good long story,
No pics but it doesn't matter.
I was 'picturing' your trip out towards Fleetwood? etc.
A good story is sometimes better than just a load of pictures somehow.
Somehow the day went a bit down hill at the end it seems.



1. Why did it do it when I eased off the power? - it was fine at full power. Someone I asked said it could be that the engine was heat soaked and by reducing the revs you reduce the cooling and the heat could remain in the engine could make it boil (dont really understand that one)

One answer.
Maybe it was already 'cooking' but you had not noticed? Or the fresh water side was cooking but not the raw side.
Its a turbo I presume?

2. Whats the chances ive damaged the engine (C H Gasket etc) and is there
an easy way to check?

Two answer that , these engines are quite tough, hopefully you have not damaged it

3. Wheres the first place I should investigate on the fresh water side? are there any common things that could cause this?

Three things, The fresh water pump could have failed.
The heat exchanger could be blocked/ duff
There could be a leak in a pipe on the fresh water side, hence the antifreeze presence.


I hate boats...

I do sometimes too

Thanks in advance for helping someone who's, well "nautically challenged"
M

Tiss a long learning and fixing curve , tiss a 'Nautical Challenge' all the time

 

[mickyb]

Thats right.. Fleetwood marina! Didn't think anyone would have heard of it.. very rainy place ive found but I only live half an hour away..

As for turbo, yep its got one of them bolted on.. hope its nothing to do with that

 

[mont]

Heat exchangers perhaps ??

fwiw,
Clearly your happy to get your hands a bit dirty.
No doubt you'll have already invested in the VP 'DIY manual' for your ad31's perhaps ????
I'd double check your heat exchangers that 'exchange heat' from the hot sealed internally cooled engine water with the external cool raw water. They are the marine version of a car radiator.
Having had three VP 'full services' on my ad41'b's (in early days of boating) they were never checked - thanks specialists. They have a tenancy over time and if the boat is stood (common) to crud up thus causing intermittant / regular overheating problems. Also they usually have a sacrifical anode (pencil type £6 ish screwed onto a stud in the cover) which usually just dissolves to nothing and needs to be fitted if your want to safeguard your engine(s) from internal electrolysis.
They can sometimes become the collector of old impellor blades as well ! Quick clean out to make sure they are exchanging heat properly and you can tick that one off the possibles. This can normally be done 'in the water' with great care as usually thay are live to water level !!!
Has been known that the end cover is put back at the wrong position giving only 50 % cooling effect as well (friends boat overheating at higher revs).
Perhaps at full revs your impellor pump has had enough grunt to force the raw water through the heat exchanger, then as you slowed down it struggled and you started to overheat. Your engine should have a temp overheat alarm switch which will suddenly sound off as soon as the temp exceeds I think 91 deg. With retained heat when you switched off this would also cause an immediate alarm as you restarted.
PS The oil cooler (if fitted) has a similar heat exchanger 'can crud up in time' system also which is a bit more involved a job and normally done on lift out as its much lower on the block !!.
PPS My black smokey ad41's cured themselves when we moved onto to Mallorcan white diesel - the uk remarkebly retained the now high price red rubbish

 

[Peanuts]

mickyb

PM on it's way to you.

 

[Chris_d]

This can be something simple, before you rip the engine to bits I've had exactly the same happen when a plastic bag wrapped around the leg and starved the engine of water, you stop in panic and it just floats away leaving no evidence, luckily I saw the bag drifting away and after a quick top up with water no harm was done.

I'd check everything, test for a blown headgasket, then go for another run to see if it starts to get hot again.

 

[neale]

As Chris says this could have been caused by something temporary like a plastic bag around the water intake. Your engine overheats and loses it coolant. You stop the engine, the bag floats away. You restart and it overheats again but this time because there is not enough coolant in the engine.

Re fill it and try it again. You may find the problem has gone away.

I would double check the impeller though, as this kind of overheat usually causes some damage to it. Impeller damage is not always obvious without removing it and having a proper look. While it's out, might as well change it anyway.

 

[H2O]

I assume you have checked the obvious, circulation pump belt.

 

[solitaire11]

sounds like a very similar problem i had some years ago, pretty sure you'll be lookin at a head/head gasket problem unfortunately.

keep us posted.

 

[gordmac]

Clean up the mess, fill it with water/antifreeze (don't overfill, leave a bit low), start and look to see where it comes out of. If you are lucky you will see where the leak is. Worth checking all the hose clips are tight and no split hoses first. If the fluid comes out of the header tank overflow chances are head gasket is away (this may not have been the original problem).

 

[hammyloz]

also what no-one has mentioned do the vital compression check

 

[Peanuts]

"For a good hour and a half I was at full chat most of the time and she behaved wonderfully! (still blowing some black smoke, and a bit down on revs"

I expect the reason for running hot is because of what you have been doing for the pass 1.5 hrs, if the boat has been in the water all season, got a dirty bottom and props, having to work at the top end for all that time, then that alone could be the reason for being hot. I do agree about maybe something blocking the inlet for a while on the outdrive (happened to me once), doubt if it's the circulation belt unless it is missing (this belt has an easier life on a 31 compared to a 32). Could of course be a restriction in part of the cooling system or just a pipe that decided enough was enough.

You mention you loosened the raw water strainer cap and water flowed out but that does not mean it is flowing freely throughout the engine, I would first check all of the sea water drains can be undone and are clear, they may need a poke with a piece of wire to clear the crud, close the drains then start the engine, check one at a time each drain to ensure a flow of water, at least you will then know you have a water supply through the engine, of course this won't tell you if it is restricted unless nothing comes out but it would assist.
Then as already mentioned in another post, I would top up the anti freeze and don't overfill, go to the 'min mark' and start the engine and look for leaks, I am almost certain you will not find one and if you were to take the boat out you could run all day at cruise but as soon as you go full throttle within a few minutes you will be running hot, back off and it will be OK, it just needs a clean underneath.

I hope this is of some help.

 

[mickyb]

Hello again, thanks for all your replies.

As for circulation pump belt, its fine.. Also the bottom of the boat is clean - freshly anti-fouled.

The black smoke is a mystery, had the injectors tested and they are fine and a marine engineer tested the boost pressure at the inlet manifold on both engines and the turbos are doing their job, the air filters are only 6 months old so the engines aren't being starved of air..

I have bought 5 gals of antifreeze so will top it up and give her a run early next week and see whether the problem re-appears - as couple of you have suggested one of those pesky plastic bags could have covered the inlet on the leg (although if this was the case wouldn't the impeller have disintegrated through lack of water??).

As for a cylinder head/gasket problem, the oil doesn't appear milky like its got water in it and the engine starts with no problems and sounds sweet.. really hope it hasn't done something as serious as that! If it has what sort of cost would be involved in fitting a new gasket?

I will keep you posted. Thanks again..
M

 

[carlton]

...as couple of you have suggested one of those pesky plastic bags could have covered the inlet on the leg (although if this was the case wouldn't the impeller have disintegrated through lack of water??).
M

Not necessarily - I had a mystery overheat last September. Engine off, leave it a few minutes, start up - all's well. I think I picked up a carrier bag around the intakes, which subsequently drifted off the drive, presumably to ruin someone else's day.

Lift-out showed impeller in good nick, but the plastic exhaust tube had melted and turned from this (left pic) to this (right pic - phone in shot to provide scale).

 

[ari]

I had an AQAD 41 overheat once. Doing 25 knots, alarm sounded, shut engine down immediately, limped home on one.

Got back, similar to you there was coolant in the bilge, raw water seemed to be doing its stuff ok.

Let it cool right down to cold, topped up the coolant (took a lot) ran it. Discovered that (what I guess is) a drain down nut had worked loose and simply let all the coolant run out. Tightened it up, had the engine checked over, all fine, no problems since (checked the nuts on the other engine too).

Just a thought, might be as simple as that, all the fresh water side draining out somehow.

I've also experienced a boat with a partially blocked raw water cooling system (or might have been a weak impeller come to think of it). Did the same as yours, ran fine at high speed, overheated when I slowed down. Speed up again (have to be a bit brave to do that) and the temperature dropped and all was well again. That was on a Caterpillar diesel but the principle is the same, basically when the impeller was whizzing around at full speed it worked ok, but not at low speed. Got it fixed and all was well.

Best of luck with it anyway.

 

[230K]

fwiw,
Clearly your happy to get your hands a bit dirty.
No doubt you'll have already invested in the VP 'DIY manual' for your ad31's perhaps ????

Where do you get these manuals please??

Thanks,

230K

 

[mont]

diy manual from any good vp dealer - price negotiable usually. It specifically for the diy owner.

 

[Pendana]

The new DIY manual covers 31 to 300 series PN 7745493 costs £31 covers all aspects of servicing.

The comprehensive Workshop Manuals is split into about 6 books and costs about £150 for all of them.

The Parts Catalogue which shows exploded diagrams of EVERYTHING with all the part numbers - including the sterndrives, is excellent value for money at about £50.

All available from Volspec and the like.

Eddie

 

[mickyb]

Hello again all

Next chapter of the story..

Filled the header tank up with fresh coolant (and also topped the other engine up at the same time), dried the bilge out and went out for another run.

Spent about 2 hours playing on the river and no over heat problems, she ran beautifully so put her to bed, went home and slept soundly with thoughts of sitting at anchor off piel island next summer with a few friends, a picnic hamper and a glass of something cold

But....

Next time I went to the boat I thought... hmm, i'll just check the coolant levels so I lifted the trap doors and saw pink antifreeze sloshing about in the bilge. A bit was under the port engine, but much more around the starboard engine (the one that had previously overheated) and it looked like it had dripped from somewhere near the turbo. The header tanks on both engines appeared to be empty of coolant.

I can only assume that whats happened is the coolant has slowly leaked from the stbd engine over the last few trips and once the level got very low - the coolant boiled and got blown out of the engine. as I say... the port engine had lost some but no where near as much as the stbd!

The other thing is, there are no expansion tanks/bottles fitted. the pipe comes out just under the cap of each header tank, is about a foot long and goes no where.. I was told though that expansion tanks are not necessarily required and this is normal Any one know different?

My first thought (before i saw the potential leak near the turbo) was that I had put too much coolant in and as it has expanded, the excess has gone into the bilge out of the pipes I mention above, but surely you would still see some coolant when you open the caps on the header tanks - they are dry!

Anyone flogging a sail boat or something with oars...?

 

[longjohnsilver]

Look on the bright side, it's not a head gasket problem from what you've told us. Just need to find where the leak is and repair it. Shouldn't be that difficult. After you next use the boat put some talcum powder on the area you think is where the leak is. That should enable you to trace the source.
Not all engines have header tanks, your arrangement is quite common, been the same on all my boats. You can always run the pipe to a plastic milk bottle to see if the waters coming out from there.
Good luck, sounds like a minor inconvenience rather than a major problem.