PS Advisor: 01/01/04

Diesel Revving
Several years ago, I was told by a diesel mechanic (following a 1,000-hour overhaul of my 62-hp Yanmar turbo-diesel) that I would be wise to rev up my engine to 3,500-4,000 rpm for a minute or so (while in neutral) at the end of a motoring journey. I have done so ever since, but I seem to be the only chap on our dock performing this maneuver.

Is there any merit to this procedure? Should I continue, or simply pull the kill toggle once I’m in the slip?

-G.E. McLaughlin
Broad Axe, PA

This is a familiar ritual—we know plenty of people who habitually goose their engines (usually under load, not so much at the dock) to "blow them out" while coming into port or after protracted times of idling or low-rpm charging. We, too, wondered whether this was really necessary, or a tradition kept alive by knowledge inertia (something we have a lot of in this game).

Here's what Mike Muessel of Oldport Marine of Newport, RI (a Yanmar dealer and Our Man In Diesels) has to say on the topic:

"I see no need to rev your engine before shutting it down. In the old days, before the better-quality engine oils were developed, some under- worked small sailboat auxiliaries smoked because of sticky piston rings caused by excessive carbon buildup. The cure for that condition was a thorough warm-up followed by a few high revs, and I suspect that's what your mechanic's advice is based on."

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Rebedding Chainplates
I'm busy replacing the chainplates on my CSY 33. I've been bedding the new 316 SS electro-polished plates down with 3M 101 sealant, but one of my buddies says that is the wrong product, and that I should have used Sika Flex with a special primer instead. Do you guys have an opinion on that?

-Dag Hanssen
Via e-mail

Chainplates will always be a big potential source of deck leaks, because they always work slightly when shroud tensions load and unload. If they're attached down below to wooden bulheads or knees, they'll eventually cause rot, which will cause weakness, which will threaten the rig. The working of the chainplates and seepage of water will eventually cause deck rot in the surrounding areas too, especially on boats where plywood or deck coring comes right up against the plates. But usually chainplate leaks are a constant minor annoyance, dripping on or guiding drips to all the things we stow along the hull sides, which are usually exactly the things we don't want to get wet.

The Sika Corporation makes a big array of adhesive/sealants that might be used to rebed chainplates, along with different primers to increase adhesion. Probably the best product in the Sika marine line for the chainplate job would be Sikaflex 292, a viscous, high-strength adhesive/sealant that, according to the Sika website, "can replace rivets, screws, welds, and other mechanical fasteners in building and repairing boats of all types."

It should be tested on the stainless chainplate—it may or may not need a primer to increase adhesion.(See www.sikaindustry.com.) Or your friend may have been referring to any of nine (by our count) other Sika adhesive/sealants, and five different primers used to support them.

While we don't have experience with the Sika products in this case, we do have some with 3M 5200, and that's what we'd recommend for the job at hand. It's a beast to work with—very viscous and thick, yet somehow very oozy at the same time, so that you can have a lot of slow-motion disasters if you're not careful. Be sure to tape off absolutely everything around the area of the chainplates, and watch your rags, caulking gun tip, and fingers—one tiny dollop of 5200 will spread itself all over everything.

However, it's a truly tenacious adhesive/sealant, with just enough flexibility to work with the chainplates, and strong adhesive properties that should prevent it from separating from the metal for a long time.

People used polysulfides for many years to bed chainplates, but that was before we had better stuff like 5200. Most polysulfides don't have the density, viscosity, or adhesive properties to work nearly as well in this application. And don't use any silicone-based product to bed chainplates. It won't stick well to the metal, it's too flexible, and many silicones have acids that can wear away at metals.