When you're motoring, your engine is constantly circulating sea water. Crud in the water can cause the engine to overheat. How to avoid problems.

Motoring with Crud in the Water

A few days ago we were motoring back to the harbor after the wind died and ran across a couple of huge patches of very coarse grass floating on the water (almost looked like large pine needles).

From past experience, we knew to watch the engine temperature closely . . . and sure enough we saw it creep up just a couple of degrees. It didn’t go into a danger zone, but we knew we had to check the raw water intake as soon as we got to our mooring.

It was almost totally full of the grass.

Motoring Your Boat When There's Crud in the Water: When you're motoring, your engine is constantly circulating sea water. Crud in the water can cause the engine to overheat.

Motoring Your Boat When There's Crud in the Water: When you're motoring, your engine is constantly circulating sea water. Crud in the water can cause the engine to overheat.

The good thing is that the grass was coarse enough that it hadn’t totally stopped the flow of water. We’d only motored about 15 minutes after encountering it, but if we’d been going very far it might have restricted flow sufficiently to cause the engine to slowly overheat.

An hour or so after Dave had cleaned out the raw water strainer, I jumped in the water to clean the bottom of the boat. Visibility isn’t great here and all of a sudden I saw what appeared to be a tree branch sticking out of the hull. Huh??

It was a big clump of the grass that had been partially sucked into the engine water thru-hull. There was so much that it hadn’t all made its way in but had just gotten stuck there. I pulled two big fistfuls out. Yikes! The problem was even worse than we first thought and I’m very glad I just happened to decide to clean the bottom before we went out again. Note to self for future: when the sea strainer is really clogged, check the thru-hull too.

It’s also easy to suck up plastic bags. Many cruising locales have a litter problem and bags that blow into the water can cause huge difficulties for boaters. We know of numerous people who did so in the Sea of Cortez. While it can happen anywhere — all is takes is one bag — be very aware of engine temperature if you encounter a patch of litter.

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  • Margaret Nelson
    Posted at 28 March 2015 Reply

    Really helpful blog. Thank you!

  • Rich Corbett
    Posted at 28 March 2015 Reply

    This post would probably have been helpful a few weeks ago when I was trying to decide on “strainers” when replacing ours. I opted for the smaller considering that I regularly clean it and rarely have it full. Now I’m thinking I should have oversized it to be safe … just another thing to keep an eye on when noticing grass, etc in the water. Thanks for the excellent post … as usual.

  • Lupari Sue
    Posted at 28 March 2015 Reply

    Good advice thanks. Where we travel it is plastic that is more likely to be a problem.

  • Rodney Lewis
    Posted at 28 March 2015 Reply

    Does your boat have one of these? I ALWAYS see them mounted backwards, with openings facing forward, as if it’s supposed to act as a scoop. But that’s totally wrong, and why they pick up crud. They should always have the slots facing aft, so the weed will pass over the bulge as the boat moves forward. It’s the suction of the pump that pulls the water in, and it doesn’t need any help.

    • The Boat Galley
      Posted at 28 March 2015 Reply

      Our previous boat had one but not this one. And good point about which way around they should go.

    • Kristine Henson
      Posted at 28 March 2015 Reply

      Good advice!

  • Sharon Gladwin
    Posted at 28 March 2015 Reply

    This is a really good reminder for me to check strainer underway especially when seagrass or debris is present. Carolyn, I always love that you don’t seem to hesitate to jump in the water !!!!

  • Charlotte
    Posted at 17 April 2015 Reply

    Sargasso grass was really prolific this year in the western Caribbean and it doesnt just affect boaters, although we too had to clean the strainers multiple times. It smell awful when it comes on to shore and in the Belize atolls they constantly had to try and rake it off the beach. The tourists who came to a picture perfect atoll couldnt stand the smell.

  • Melinda Taylor
    Posted at 01 April 2016 Reply

    You need a deeper intake

    • Carolyn Shearlock
      Posted at 01 April 2016 Reply

      There’s still a lot of crud that’s 6 inches or more under the surface!

  • Stephen
    Posted at 06 August 2016 Reply

    Easy to make assumtions or generalizations.
    This information on strainers, from an industry professional, is worth a read.
    Especially the section on external strainers.

  • Richard Armstrong
    Posted at 15 September 2016 Reply

    Steve D’s comments directly contradict Rodney Lewis. Think I’ll go with Steve. Nothing personal, Mr. Lewis.

  • Peter bould
    Posted at 18 September 2016 Reply

    We also use an Aqualarm water flow sensor. Has saved our engine a couple of times

  • Debbie DeLaune Richey
    Posted at 07 October 2016 Reply

    This is good advice no matter where you boat. We see eel grass mats, driftwood chunks, etc in the PNW waters. Especially during extreme high tides and in the winter during flooding season from the rivers. During crabbing season you also need to watch out for crab pot floats. Those can be difficult to see if there is any chop in the water.

  • Joyce Johnson
    Posted at 08 October 2016 Reply

    We saw a lot of stuff in the water in California after the Japan tsunami. Our harbor had really weird currents for several days after. Our electric boat could hardly handle the currents.

  • Brian Kepner
    Posted at 31 July 2017 Reply

    Lesson learned.. TY

  • David Warbach
    Posted at 31 July 2017 Reply

    I’ve not experienced this in salt water but on fresh water small sticks and twigs absolutely foul intakes/impellers. it’s a nightmare trying to clear out a stuck something on a ski especially if there’s no shore nearby.

  • Shelley Stevens Ruff
    Posted at 31 July 2017 Reply
  • Ron Gamache
    Posted at 01 August 2017 Reply

    has anyone thought about a radiation detector for the pacific

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