It was half an hour before the boat was due to be hauled out. The new engine was due to arrive tomorrow. It was all going to be very expensive.
And then a woman I had never met before knocked on the coachroof: “I’ve been reading your blog. Your overheating trouble: Have you looked at your exhaust elbow? That’s what it was for us – just thought I’d mention it…”
I wish I knew her name. I’d like to thank her.
As readers who have been paying attention will know, Samsara’s venerable Nanni 21hp has been running hotter and hotter over the past several years. By the time I arrived in the Isle of Man, I had to sail into the harbour and then get a tow into the marina.
A succession of engineers pored over it at various times. All of them sucked their teeth and shook their heads. They examined the impeller; they suspected the heat exchanger. Nothing they did made the slightest difference.
I tried muriatic acid. I tried citric acid. I kidded myself there was a slight improvement.
I waited six days for the charmingly encouraging Pat Ryan to get one of his lads to have a look. In the end, I phoned Rab McCluskey in Douglas, who had been so keen on the heat exchanger. We came to the mutual conclusion that it was a 20-year-old engine. Maybe the time had come… it had given good service… every machine has a finite life…
The new one was going to cost just over £5,000.
I winced, but what could I do? I emptied the savings account.
Nobody had mentioned the exhaust elbow. Actually, I had never heard of the exhaust elbow.
And yet I heard about it a second time half an hour later. Scott Nelson, the Boatworks yard manager, hadn’t even got Samsara onto the slip when he said: “Before you go to all the trouble and expense of a new engine, I just wondered: Have you looked at your exhaust elbow?”
So we did. Bob the engineer took it off. It really is an elbow – a little right-angled piece of rubber hose, except it seemed to have lost its flexibility – hardly surprising when you considered that it was completely choked with carbon.
Honestly, you couldn’t see daylight through it. The tiny hole in the picture is only there because Scott poked it with a pencil.
“Can you cancel the new engine?” he said.
Actually, that was remarkably easy. It wasn’t about to arrive tomorrow. It was still in Holland.
Now I’m in Torquay, looking at YouTube videos about how to change your alternator and with a new mantra to remember: Diesel engines need to be run hard from time to time…
The exhaust elbow (or if it has another name, I don’t know it). The little hole wasn’t there when we first took it off.
Surprised that it took so long to diagnose. Regular removal and cleaning of the exhaust elbow, yearly or after 250 hours, and replacement after two years is recommended by all (most?) marine diesel engines manufacturers! I think that this last is a bit extreme, particularly as they can be quite expensive on newer engines, but definitely remove and inspect every two years. Apart from anything else, a blockage here can cause extensive engine damage, even if not completely blocked.
I had this problem with a generator on my Cheoy Lee, it was easy to find though as the exhaust broke at the elbow, completely bunged up which is surprising as diesel generators run at fixed speeds, still it was 28 years old.
Alternators, do check the output is correct if you are using AGM or Lithium batteries, charging regimes are quite different from Lead acid. Easy to get the alternator output changed.
Regards,
Leslie
It’s OK, the alternator charges the AGM engine-start battery and the new one is the correct model for my engine.
Yanmar recommend running at high revs for a few minutes for every 30 minutes of low revs, idle or tick over, and revving hard in neutral 4 or 5 times before cutting the engine at the end of a cruise.
I understand that this is intended to burn off coke deposits in the exhaust elbow, where cooling sea water is mixed with exhaust gases.
Engines and mechanics, that combination that the devil refuses to accept.
The engine of my boat, a Volvo MD2040, also overheated. After many mechanics, the heat exchanger had been replaced, as well as the saltwater pump, the saltwater filter, all the water pipes, the exhaust manifold and the thermostat. Result: it continued to overheat.
It was dismantled, completely overhauled and repainted. €8,000 later, I had a beautiful engine that overheated just like before. In desperation, I started asking for quotes for a new engine.
By chance, I had the Saildrive seal replaced, which, at 22 years old, had long since passed its expiry date. And voilà. The problem was in the Saildrive (the cooling water passes through the interior), whose interior was clogged with the remains of marine animal shells.
If you are dealing with alternators, consult these people. Cheap and the best information I have ever found. https://www.morganscloud.com
Many Volvo Saildrive owners fit a new skin-fitting, seacock and water strainer for seawater cooling, exactly because of this problem.
VERY old joke: “I want to complain about this bill for fixing my car. I hear you just tapped the side of the carburetor with a hammer. How can you possible justify £20 +VAT?”
“Very sorry sir. Let me correct that for you”
“tapping the carburetor with a hammer £ 0.50”
“knowing what to tap and where to tap it £19.50”
“plus VAT”