Seachest fouling

13 years 9 months ago #569 by Chris Grimes
I am having problems with growth in my seachest. I put a new
raw water strainer (Vetus I think) but seagrapes are
showing up in the seachest. The seachest has a plexiglass
cover held down by about 20 bolts with a bed of some kind of
sealer (probably since it was built in '86.)

Has anybody had experience removing the cover? Any comment
on the appearance of marine growth. We are in Narragansett
Bay, which is record warm this year.
Chris Grimes Ar n-Inin
>> #331

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13 years 9 months ago #589 by Lisa Cornelius
Replied by Lisa Cornelius on topic Re:Seachest fouling
Hi Chris,

I have the same sea chest on hull 332. We have no fouling. What about some Chlorox into the strainer and sea chest? and let it sit for 15 min.

Best NOT to touch the bolts or top unless you want to redo all of it over ...very very well. 20 year old plastic can crack with any stress.

Please be very careful removing the top. We had a serious problem with an air leak. I stupidly (mostly we do it to ourselves) forced water from a garden hose into the refrigerator water cooling output to "clean it out". Weeks later in the Potomac River far from home, the engine began to overheat. We were puzzled. We saw minimal cooling water coming out the back. We traced the problem and looked at the sea chest. It was nearly empty of water (full of air). We were amazed that this could be. The sea strainer was clean. The intake did not have a piece of plastic or jelly fish covering it. I did actually risk my skin to check that in jelly fish infested waters. When we would stop the engine the sea chest would fill. Then, at random times the sea chest would be full of air again just when we needed the engine most. Higher throttle emptied the sea chest faster sometimes. ...sometimes...
How do you figure this one out? What is the pattern?

FINALLY, we realized that the one way valve for the refrigerator cooling line had been damaged weeks before by me.
It allowed air into the sea chest ONLY when the the refrigerator was not on. The refrigerator cooling line was sucked clear of all water by the powerful suction of the engine water pump,Then the line was just a source of air. Months before we had removed several broken off zincs (third party wrong type) that had erroded off and fell inside the cooling system. We cleaned the Heat Exchanger cooling tubes with a rifle cleaning brush and put on a new water pump. Put on a newly fabricated stainless steel raw water output tube. We greatly increased the cooling flow of the Volvo Penta MD30A engine. Before, for 21 years, Bob (the first and only owner) must have not used the engine at near full power.

I have removed the front head. No more raw water lines to forward. I have a ball valve on the Propylene Glycol fill line inside the wet locker. This keeps air from coming in and can burp the sea chest in emergencies. Just blow in to remove any water from the fill line and allow the sea chest to refill with engine OFF. Remember to close the valve (Thanks Al Hales) I have a new one way valve in the refrigerator line. AND the only other line from my sea chest is the line to the aft head. Now, If we forget and leave the toilet on water mode...AIR CAN STILL LEAK INTO THE SEA CHEST. We have to remember to keep the valve on the toilet in DRY MODE. I plan on installing another ball valve in that toilet line near the sea chest as a back up to the toilet valve. I have the valve but worry about my damaging other systems to put it in. I must be in the right mood to do it.

Patrick Cornelius 302-286-7134 or cell on boat 302-981-0237

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13 years 9 months ago #591 by Lee Davis
Replied by Lee Davis on topic Re:Seachest fouling

I have a Brewer 44 (Hull #268) so my raw water configuration may be slightly different than yours. Have one through-hull supplying a dedicated strainer just for engine raw water. Another through-hull with sea strainer supplies the sea chest which supplies sea water to the generator, refrigeration, galley, heads, etc. My sea chest became fouled with worms and grass while in Hawaii. Had a big problem with the generator or refrig starving the sea chest while operating so had to do something. Tried the clorox bit to no real effect. So.... I took off the cover to the sea chest and cleaned the sea chest completely. Not a fun task, but doable. It was amazing the amount of growth, sand, mud, etc. that had accumulated over the years in the bottom of the sea chest. I was able to re-use all of the bolts, nuts, washers. I used RTV to re-bed the cover on the chest prior to bolting everything down. No air leaks, so everything worked as advertised upon re-assembly. Good luck !

S/V Head Out
Brewer 44 #268

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