DIY re-powering

Nov 17, 2017 Boat Maintenance ,Technology

Maritime lore is littered with DIY repower projects that start with zeal and enthusiasm, only to end with chill pills and high bills. And yet, sometimes the planets align, writes LAWRENCE SCHÄFFLER.

When Auckland’s Paul Leydon bought his Allan Wright 1280 Sweet Disorder 10 years ago, she met his every need – spacious, comfortable, easy-to-handle and a joy to sail. But there was one niggle – motoring into a feisty sea quickly reduced things to a crawl.

Her 40hp Volvo diesel was woefully inadequate for punching through the waves – and that tended to cramp Leydon’s cruising flexibility. A bigger engine – a 55hp Volvo – moved to the top of his Christmas wish list. And the bigger, 120-amp alternator would be a welcome ally in keeping Sweet Disorder’s batteries ship-shape.

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“My wife and I are committed sailors,” says Leydon, “but as you progress through life you eventually come to accept that you’re not as fit and strong as you once were. When you retire, your focus tends to shift away from race-mode. So there’s more motor-sailing, and extra horsepower is a significant bonus.”

He had intended to have the transplant tackled professionally – by Lees Boatbuilders at Sandspit, north of Auckland – but that idea quickly died when owner Greg Lees pointed out that the yacht’s 2.2m draught was too deep to use the yard’s haul-out facility. The job defaulted to Plan B – a DIY, self-install.

“Even though I tend to the yacht’s maintenance needs myself – oil changes, filters and fan-belts – by no stretch of the imagination could I call myself a marine engineer. An engine swap was a fairly daunting prospect. Fortunately, I’m semiretired so I have plenty of flexibility.

“Part of the logic in going with another Volvo is that the new engine has a virtually identical footprint – I didn’t have to worry about altering the engine bed or the mounts. The bigger engine came with a bigger sail-drive, but again, this unit slotted seamlessly into the existing mounting. And I could use the existing throttle and gear cables.”

A key component of Leydon’s strategy was minimising costs and hard-stand time. This shaped his approach to engine removal and replacement – the swap would take place with the boat in the water at her Gulf Harbour berth. Only the sail-drive changeover would require a brief haul-out.

The first part of the operation proceeded smoothly. A $75 come-along from Repco helped to coax the old engine forward
off its bed and into the saloon. Leydon then used the yacht’s boom to lift the 180kg engine through the companionway, into
the cockpit and then over the side and on to a pallet on the pier alongside. It was sold to a chap who needed it to complete a
repower of his catamaran.

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Installing the new 55hp engine was a reversal of the extraction procedure. “It required one small modification to the boat,” says Leydon. “I had to remove a small sliver of an engine-room casing to accommodate the new engine’s bigger sump.”

The bigger engine also required beefier plumbing – raw water intake and exhaust – and Leydon says two companies were particularly helpful with free advice: Auckland’s HCD Flow Technology (fitting the right quality exhaust hosing) and PowerFlow 2000 (the exhaust system).

“John at PowerFlow was remarkably patient with me – I’d never heard of ‘back-pressure’, much less knew what it was or why it was important. He explained it all in easy-to-understand language. Even better, he offered helpful and cost-effective
solutions to my problems.

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“I took the old fibreglass water-trap to him and asked if he could make another, but with bigger flanges for the new hoses.

“He said he could indeed make a new box, but it would be far cheaper if he simply cut out the old flanges and glassed in bigger ones. I’m not naturally a cynical person, but someone turning down an opportunity to make a better profit was a pleasant surprise.”

Any engine transplant, of course, wouldn’t be worthy of the name if it didn’t run into at least one snag and, inevitably, one materialised in a sneaky fashion.

“Through a convoluted misunderstanding with Volvo, I installed the new engine without its ‘spline adaptor’ – a small piece of kit that accommodates the diameter difference between the engine and the sail-drive’s input shaft.

“When I started the engine for the first time, it ran beautifully and water spurted enthusiastically from the exhaust outlet. It all looked great. But when I put it into gear – nothing. The engine and sail-drive’s spline weren’t engaging.”

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With the problem identified and the spline adaptor retrieved, Leydon and his helpful come-along inched the engine forward just enough for the adaptor to be installed. With everything bolted up again, Leydon started her up and nervously shifted the gear lever forward – sweeeeeeeeeeet!

“I don’t yet have precise fuel consumption figures – but to be honest I’m not really fussed about the difference. I wanted more power.“At a cruise speed of five knots the old engine used to run at about 2,200rpm, using two litres an hour. To get to six knots I’d have to increase that to 2,500rpm. It maxed out at 3,200rpm – for very little gain in speed and a massive increase in fuel consumption. But the problem was motoring into rough seas – she just stopped dead.

“With the new engine, she does 3.7 knots at 1,000rpm, 5.7 knots at 1,500rpm and at 2,000rpm she’s doing seven knots. So while the new engine is probably using a bit more fuel, it’s revving far lower.

“More importantly, the boat powers through the seas now. This has made a huge difference in how we use the boat. It’s affected our cruising patterns and lifestyle – giving more flexibility to make snap decisions.

“We can now tackle conditions – with confidence – which we might have thought twice about before. It gives us access to places previously out of range, and we can now keep up with friends when we go cruising – no more lagging behind.”

Perhaps the most important benefit of the transplant, he adds, is the one that isn’t immediately obvious.

“It’s been a new, fascinating experience and I’ve enjoyed it – I’ve grown with the boat. And that’s significant because it’s extended our time with her. It means we will keep Sweet Disorder until we are no longer able to go cruising. We won’t have to invest in a launch.”