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Q&A: Recurring Rust Spots, Insurance for Old Boats, Hose Clamps (Vol. 3)

Your technical questions answered by some of the most experienced trawler minds on the water.

Q: I have a 2008 Mainship 34T. The engine is a Yanmar 6LYSTP. So, age is 13 years and hours are 1,630. In 2018, I noticed rust spots on top of the exhaust elbow (figure 1). 

Figure 1

Figure 1

This suggested that the elbow had corroded and could be due for replacement. So, I opened the elbow, and the inside looked really good (figure 2). At that time, I was informed on a Mainship forum that if the elbow was stainless steel, it should have a much longer life than a cast iron elbow. So, I painted over the spots. Two and a half years later, the rust spots are back, so I sanded the spots to see if the rust is superficial—which it looks like it is, as the sanding seemed to remove everything.

Figure 2

Figure 2

Is superficial rusting normal behavior? I’m sure my local dealer would tell me to replace the elbow. If I leave it, I assume that any failure would be gradual, not catastrophic. I have seen mention of 2,000 hours as a reasonable life for an elbow, so 1,600 should be good for another three to five years, right? —Anonymous, North Vancouver

A: While it is certainly true that exhaust elbows lead a challenging existence by mixing furnace temperatures with corrosive seawater, and they do have a service life, I agree with you that the interior of yours looks good. What is sometimes difficult to tell is the wall thickness in the interior of the water-injected part of the elbow. It is possible that there is a slight porosity in your casting, but it looks more to me like the heat has just caused the paint to fail, and the normal humid conditions in the engine room have caused the rust to start. I think your actions of sanding the rust and repainting are sound as long as you continue to monitor the elbow for a quick return of rust or any weeping of water, indicating there might be a crack starting. —Max Parker, Zimmerman Marine

Q: I am a new owner of a Grand Banks 42 1999. She is beautiful and in great shape, but no one seems to want to insure a 20-year-old boat nowadays. The quotes are outrageous ($4,000 plus). I have been with USAA for 30 years with no claims. They sent me to Progressive, which just canceled my policy because she is 20 years old. What, if any, are my options? —Anonymous, Norwalk, Connecticut

Grand Banks 42

Grand Banks 42

A: The insurance market is cyclical, and we are currently experiencing a very hard market. Many people forget that boat insurance rates decreased year over year from 2007 to 2017. Those unsustainably low premiums caused most insurers to exit the marine sector after the devastating impact of the three major hurricanes in 2017. Subsequent hurricanes have further compounded the problem. The handful of insurers that stayed in business raised premiums to ensure sustainability. Even if you never filed a boating claim, all boaters are still susceptible to the industrywide rate increases, unfortunately.

However, the vast majority of boats on the water are insurable. If you’re looking for an edge, working with a marine insurance specialist broker is an option. These brokers have access to all underwriters, so you’ll theoretically receive a quote from all insurers, which gives you a much better scope of market. The premium remains the same when you work with a broker, and you’ll benefit from having an advocate to assist in the event of a claim. If the objective is to keep the price down, Southeast boaters might consider changing their navigational plans for 2021. Instead of staying close to your home port this hurricane season, consider moving the boat north for the summer. Not only will this move capture the interest of more underwriters, it will also decrease the annual premium. —John Jarvie, Oversea Yacht Insurance

I was delighted to read Capt. Bill Pike’s Pro Tip of the Month on hose clamps [March 2021]. I have been there, done that, and I advise all my boating buddies to do the same. When you can, replace them all, or at least make sure they are snug and not cutting into the hose. As a follow-up to this great advice, I’d like to offer my own two cents.

Every 20 or so hours, I check all my clamps. And, having taken Capt. Pike’s advice, I recently changed every one out and now only have two different sizes, the larger sized T-torque (constant torque) type as OEM on my vessel’s Caterpillar C12s, and the smaller standard Ideal stainless clamps for all other fittings such as the air conditioning unit, water system and bilge pumps. To ensure that I have made my complete rounds on both engines, the genset and all other systems, my handy set of paint pens comes out, and each clamp is color coded, noting that it was checked. I mark the screw or bolt head with the paint pen, and the mark will last for quite some time. Any sign of cracked paint will also be an indicator that the clamp has loosened, or even (I have seen it happen already) failed.


It’s just one more simple step to ensure that your rig stays in tip-top shape, and makes it so much easier to ensure that you hit all the necessary parts at required intervals. Also, at the same time that I do the clamp checks, I also check my zincs and mark the zinc caps with the same paint pen. I keep an inventory of prepainted zincs (predabbed with Bostik Never-Seez), ready for a speedy change out. —David Mahler, Bellmore, New York