Isolated Prop Shaft

Ask Sail: I have installed a shaft-saver coupling on the prop shaft on my sailboat and have realized the shaft is now isolated from the ground. Is this a good thing, or should I put a grounding strap on the coupling?
Author:
Updated:
Original:

Gary McKinney of Loon Lake, Washington, asks:

asksail_propshaft

I have installed a shaft-saver coupling on the prop shaft on my sailboat and have realized the shaft is now isolated from the ground. Is this a good thing, or should I put a grounding strap on the coupling?

Nigel Calder replies:

The primary objective is to tie your shaft and propeller into your bonding circuit and an attached zinc anode to prevent galvanic corrosion. This requires an almost electrically perfect connection from the shaft to the zinc, so the critical issue is the electrical path from your shaft-saver to the zinc, which should be via a #8 AWG or larger cable with good connections at both ends. In order to protect the shaft and propeller, you need not tie the engine into this circuit—i.e., you don’t need the ground strap on the coupling. This is done to create a path to ground in the event of a lightning strike. The science in this respect is murky, so I’ll leave it up to you to decide if it is necessary!

NigelCalder

Have a question you'd like to ask our experts? Email us at sailmail@sailmagazine.com!

Related

IMG_8287GR16Mykonos

Cultural Charters: Mykonos

In last month’s column, I covered the amazing mix of cultures that have called the Dalmatian Coast home over the centuries. Croatia cruising is like a smorgasbord of intertwined centuries, and the islands are a movie set. A little farther south, though, you’ve also got Greece, ...read more

cookinglead

Cruising: No Oven? No Worries

Many cruising boats, especially smaller ones, don’t have a conventional oven. But that doesn’t mean that you can’t have all the baked foods you want, from bread to brownies to breakfast rolls to casseroles and even a roast chicken. All it takes is the right bit of gear and a ...read more

TOTW_PromoSite

SAIL's Tip of the Week

Presented by Vetus-Maxwell. Got a tip? Send it to sailmail@sailmagazine.com Take no chances  This is my stern with the engine running slowly in gear against the lines. We all know that when we’re charging batteries this lets the engine warm up thoroughly. However, I have a ...read more

ZK-Seaboot-900

Gear: Zhik’s Seaboot 900

A Better Sea Boot Following up on its successful ZK Seaboot 800, Zhik’s Seaboot 900 was created in partnership with team AkzoNobel and Dongfeng Race Team, the latter the overall winner of the 2017-18 Volvo Ocean Race. Designed for serious, long-distance offshore racers and ...read more

01-LEAD-FP-Astrea-42-Gilles-martin-rajet---Navigation

Switching to Solar Offshore

No sensible bluewater sailor would consider setting off on a long cruise these days without some means of generating power other than by burning fossil fuels. The good news is that solar energy is becoming less expensive by the day, making it an obvious answer for providing the ...read more

190812-Tiwal-Video-600x

Video: Tiwal Cup 2019

Who says you need a superyacht to have fun? It would be hard to imagine having a better time on the water than these sailors recently did racing aboard a fleet of Tiwal inflatable sloops. ...read more

GEMINI-BATTERY-PASSAGE

Experience: No Batteries, Big Problems

After sailing on Puget Sound and in British Columbia for over 30 years, my wife, Jeri, and I retired to Florida, bought a house on Punta Gorda and worked hard to get it straight. The walls had been painted, furniture bought and assembled, belongings packed, transported and ...read more