Author Topic: Strut Coating  (Read 4525 times)

Dolce_Vita

  • P323
  • Hero Member
  • *
  • Posts: 553
  • Karma: 9
    • View Profile
    • S/V Dolce Vita
  • Model: P323
  • Vessel Name: Dolce Vita
  • City: Pasadena
  • State: MD
Strut Coating
« on: May 23, 2018, 09:27:48 AM »
The bronze prop strut on my P-323 appears to be coated with something to prepare it for painting.  The material is white and is approx. 1/16" thick.

Some of it has flaked off of the bottom portion of it housing the cutless bearing, exposing the bare bronze and allowing it to begin corroding. (Yes, it is bonded, and I have zincs on the shaft).

I've done a lot of online research, but been unable to find any clear guidance on coatings for struts.  Some sources say to never coat it, especially with copper-based bottom paint. At least one suggested clear epoxy.  Others suggest Interprotect-2000, and then bottom paint.

I have examined all of the other struts in our boatyard, and they all appear to be coated and bottom-painted.

Any ideas?
« Last Edit: May 26, 2018, 05:40:05 PM by Dolce_Vita »
@(^.^)@  Ed
1977 P-323 #42 "Dolce Vita"
with rebuilt Atomic-4

popeye323

  • P323
  • Jr. Member
  • *
  • Posts: 30
  • Karma: 1
  • P323 Enthusiast
    • View Profile
  • Model: P323
  • City: Falmouth
  • State: MA
Re: Strut Coating
« Reply #1 on: May 23, 2018, 08:57:06 PM »
Too funny. I noticed the same thing this weekend while I was stripping bottom paint off the prop and shaft. I have had the boat many years and I could not remember if it was something I did while I was applying epoxy to the bottom.

selene

  • P323
  • Hero Member
  • *
  • Posts: 365
  • Karma: 6
  • Mighty Member
    • View Profile
  • Model: P323
  • Vessel Name: Selene
  • City: Redwood City
  • State: CA
Re: Strut Coating
« Reply #2 on: May 24, 2018, 01:35:56 PM »
I think that there is no consistent approach.  Like you, I researched it, and came up with the same options - leave it alone, epoxy, Interprotect, bottom paint, etc. And when I wandered around the boatyard, I saw all the variants described.

FWIW my strut is Aluminium, and has bottom coat painted on - which never lasts.

I wonder what could be causing the corrosion; bronze is normally pretty durable.  It is bonded to the rest of the grounding? Could you have some stray current?

Sorry not to be more help :-(

Dolce_Vita

  • P323
  • Hero Member
  • *
  • Posts: 553
  • Karma: 9
    • View Profile
    • S/V Dolce Vita
  • Model: P323
  • Vessel Name: Dolce Vita
  • City: Pasadena
  • State: MD
Re: Strut Coating
« Reply #3 on: May 26, 2018, 07:44:04 AM »
Yes, the strut is Bronze, and bonded to all the other hardware.  I measured the resistance from strut to shaft and it was around 2 Ohms, which seems reasonable, given the length of bonding wire involved.

Two large zincs on the shaft, about 2" forward of the strut. 

Based on the boatyard's recommendation, I'm going to try coating it with Pettit Zinc Barnacle Barrier.  The yard claims it has better adhesion on bronze than interprotect-2000, and it holds up on my prop very well.
@(^.^)@  Ed
1977 P-323 #42 "Dolce Vita"
with rebuilt Atomic-4

Rusty Pelican

  • P323
  • Sr. Member
  • *
  • Posts: 238
  • Karma: 5
  • http://rustypelican.blogspot.com/
    • View Profile
  • Model: P323
  • Vessel Name: Rusty Pelican
  • City: Hingham
  • State: MA
Re: Strut Coating
« Reply #4 on: May 26, 2018, 07:58:23 AM »
I have been using it for 5 seasons; works great

Alma

  • P323
  • Hero Member
  • *
  • Posts: 332
  • Karma: 9
    • View Profile
    • GeneSmithStudio
  • Model: P323
  • Vessel Name: ALMA
  • City: Forked River, NJ
  • State: NJ
Re: Strut Coating
« Reply #5 on: May 29, 2018, 09:49:44 AM »
Look into "PropSpeed" pricy but lasts a few years. I never tried it but many BIG powerboats use it to keep all running gear clean.  https://oceanmax.com/marine-products/propspeed/product-information