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Coast Rider's picture
Coast Rider
Last seen: 2 weeks 4 days ago
Joined: 10/17/14
Posts: 40
Stop corroding macerator bolts with zinc.

My macerator is falling apart after 2 years. The long narrow bolts holding the unit together are simply corroding and breaking away. Other boaters say the unit has a 2 year life span. Another boater says the culprit is electrolysis like what attacks a prop shaft. We install zinc slugs on the prop shaft to stop this. Might the same work on the macerator? Perhaps attaching a zinc slug to the macerator will stop this corrosion?. Maybe I can increase the life span of my macerator with a zinc attachment. I could use a circle clamp to attach the zinc. What do you think ??

Joe Lucido
1986 Catalina 36
Hull # 0625
M-25 Universal diesel
Oceanside, CA

Joe Lucido
1986 Catalina 36
Hull # 0625
M-25 Universal diesel
Oceanside, CA
Last seen: 1 day 18 hours ago
Joined: 7/27/12
Posts: 236

If you have an electrolysis problem, you need to solve it as it will eat more expensive things than your macerator.

Nigel Calder wrote a process on how to troubleshoot this and I was able to easily and quickly isolate and resolve the problem by following his test proceedures.  All you need is a cheap multimeter and an hour or two.  He has his own books and his work in used in the electrical section of many comprehensive manuals.

I would be very wary of advise from supposed professionals and internet know it alls.  I got bilked $1,100 by a 'professional' marine electrician.


2000 C36 MKII 1825

Haro's picture
Last seen: 22 hours 22 min ago
Joined: 11/7/14
Posts: 191

My macerator bolts also failed and the unspeakable filled the the bilge.
After I purchased a new one, I replaced the 4 bolts with stainless steel screw rods. No problem after 4 years.
The reason the bolts broke, I think, was mostly because it was not installed properly.
The macerator must have a flexible hose attatched to its intake side. Originally it was attached to the holding tank with a "PVC "T" splitter. As the hull flexes the impleller houseing causes the bolts to break.
I added a 3-way valve, as it is needed to develop vacuume while using the pumpout hose. Also if the macerator bolts break there will be no spillage from the holding tank.

To pass Cost Guard requirement in protected waters - the valve handle must be secured with a zip tye in orienatation that closes the macerator intake.

Sail La Vie 1999 Catalina 36 MKII, M35B-17031, Coyote Point, San Mateo
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