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Not loving that alarm sound

Posted by on February 21, 2012

We waited till midday today, the high tide, before raising anchor in West Arm to set off for Georgetown.

We had books to return, groceries to buy, per-ordered cryovacced and frozen meat to pickup from the butcher… You know, things to do!

Less than 10 minutes later, the dreaded water alarm cut in…

I must admit I thought we had seen the back of that problem when we sorted the thermostat issues… But apparently not.

We hurriedly dropped 10m of chain in 4m of water, and killed the engine. The engine temperature gauge wasn’t registering anything, despite earlier attempts to fix it, so no information there. There was little water coming out with the exhaust, and the impeller housing was hot. Expecting a stuffed impeller, Lis whipped the cover off to find… A perfectly okay, new looking impeller!

As it looked like the problem was going to be a bit more tricky to solve, we ran out some more chain, and advised people expecting us in Georgetown that we may not show. We had until 4pm to get out of our spot before we wouldn’t make it over the shallow bit in the falling tide.

Lis started a methodical check of the engine’s water circuit. First off was the forward zinc housing. That revealed a stuffed zinc and a gallery full of calcified crap completely covering the engine temperature sensor (that explains why that wasn’t working!). I spent 15 minutes of chipping it out with a screwdriver and installing a new zinc, while Lis dropped the alternator off to get at the second zinc. That checked out fine, and she re-tensioned the alternator and put the newly cleaned panel with its clean sensors and zinc back in place with a fresh gasket. Then she checked the thermostat housing. Nope, all good there.

Then came the tough one… The panel at the back of the engine. Lis spent a few minutes limbering up and completing a stretching routine to prepare her body for the contortions required to get around the side of the engine in the engine bay…. Okay maybe she didn’t, but she was none too confident about being able to get in there, so we enlisted the help of one of smaller children to assist. Damn handy things, kids, they can get into all sorts of tight places!

With Lis in, Alex all keen and already in there unbolting the required panel, I was relegated to passing tools in on request. The back zinc, which wasn’t been changed in years was less than half gone and the water gallery was fine… So that wasn’t the problem, either.

Hoping that the completely choked first panel was responsible for the blockage, she did everything up. We made sure the engine was good to go and there were no spare tools or such lying about to get caught in the engine, and fired her up.

Exactly 8 minutes later, she went into alarm. It was 3:30pm. Shit.

Time to phone a friend…. Our good mate Kerry Williams is the Cummins rep for southern Tassie and has forgotten more about diesel engines that we’ll ever know….

Lis got him on the phone…explained engine overheating.”It’s the impeller”, he said.

“Nope, checked that, it seemed good but the housing was hot”, we said.

“It’s the impeller, check that it’s not slipping on the keyway”, he said.

So we checked, and knock me down with a feather, the metallic bush on the impeller freely spun inside the rubber impeller wheel. The little bastard!

New impeller in, we gave it a start, and shazaam! It worked… No alarm anymore, and hey it’s 3:55pm!

We quickly raised anchor and set off, and guess what? The engine temperature gauge is now working again. Yay!

Here’s a photo of the offending part:

20120221-205148.jpg

3 Responses to Not loving that alarm sound

  1. Andy

    Hear hoofbeats, expect horses NOT Zebras.

    The joys of Engineering assumptions.

    Have fun, off to work until mid May, will try and catch up with you all where ever you end up.

  2. Richard and Wendy

    Thanks for keeping me sane. This happened to a little Johnston outboard once – the one we have still. I was pleased to get a new water pump for Charon last year – less than $350 complete from the UK. Its a reassuring feeling to have a good stream when you get to my age. Impellars are amazingly robust and after a year (when i routinely replace mine) they seem as good as new.

    Unfortunately the impeller on the Gen Set (Yanmar) had stuck after returning to Charon last year and starting the engine resulted in tearing off EVERY vane. No water coming out, shut down and reinstall a new impellar with lots of slimy stuff. This year – I will take them out first and make very slippery – in fact I should have taken them out BEFORE we left the boat. An oversight.

    Keep up the good blog. Look forward to your posts.
    R

  3. Robert Huitema

    Hi Guys,

    We too have had similar issues – but Motu is powered by an outboard, and the slippage was in the prop bush. She had a Yamaha High Thrust 8hp then, and of course we were in remote Great barrier Island, 6 hours from Auckland.

    The engine ran fine, revved impressively, but no go. Lift the engine up to inspect the prop and sure enough it spins and looks good. Put it in the water and get 1knt max….eventually lifted it out and found with force the prop could spin on the bush. It had enough friction to look good in air, but with the weight of a boat in the water it just slipped….we now have a well mannered Honda 50hp. Much more expensive than an impellor too:-(

    Cheers Rob