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Old 10-11-2019, 21:56   #1
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Painted engine components... Why?

I'm a new boat owner and was doing some engine maintenance which sparked a few questions. A previous owner was supposedly a helicopter mechanic and I found the spark plugs and some bolts were painted black. I'm wondering why this was done.

I understand painting the engine block for protection but these components were painted black rather than matched to the existing paint color and I'm wondering if there's some significance to that fact (not just the color, but could it be a different type of paint or something that isn't paint at all?)

What's more, there are two parts on the block which are painted don't seem to be components which seems odd and I'm curious as to what the reason would be.

This might just be artistic flair but in other areas of the engine, the previous owner demonstrated what seems to be methodical efficiency so I'm inclined to think there's a reason.

I did find references on a machinist forum to something called black oxide but the process of applying it doesn't seem to jibe with the finish I see on my engine components.

Hopefully someone can help me peer into the previous owner's mind and get a better understanding of what's going on here. Many thanks!
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Old 10-11-2019, 23:56   #2
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Re: Painted engine components... Why?

The previous owner thought it looked nicer. Probably to make the boat more attractive to a buyer.
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Old 11-11-2019, 01:39   #3
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Re: Painted engine components... Why?

My guess is the owner only had that one color of paint on hand or was unable to match the paint of the engine. So he painted those parts before he put them on. That’s just a guess.
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Old 11-11-2019, 02:01   #4
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Re: Painted engine components... Why?

Could be high temp BBQ paint, which is often black although it comes in a few other limited colors but none probably not an exact match with the original engine color. Black seems to make sense and goes with anything. Cheap and available at most hardware and big box stores.
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Old 11-11-2019, 02:47   #5
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Re: Painted engine components... Why?

Targets with the correct emissivity for accurate readings with an IR thermometer to monitor engine termperatures?
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Old 11-11-2019, 02:51   #6
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Re: Painted engine components... Why?

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Targets with the correct emissivity for accurate readings with an IR thermometer to monitor engine termperatures?
Good idea...I need to try that.
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Old 11-11-2019, 03:48   #7
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Re: Painted engine components... Why?

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Originally Posted by Poche View Post
Good idea...I need to try that.

Cheap IR thermometers have a fix emissivity calibration of around 95% - and that's close to the emissivity of matt black paint.


Th OP's shiny engine will have a much lower emissivity and an IR thermometer will display a temperature that is quite a bit lower than actual operating temperature.



Black electrical tape patches stuck on various parts of the engine are a not un-common method of achieving the same thing.
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Old 11-11-2019, 04:09   #8
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Re: Painted engine components... Why?

He painted the parts after Labor/Labour day.
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Old 11-11-2019, 04:18   #9
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Re: Painted engine components... Why?

Why not try to ask the PO?
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Old 11-11-2019, 07:51   #10
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Re: Painted engine components... Why?

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Cheap IR thermometers have a fix emissivity calibration of around 95% - and that's close to the emissivity of matt black paint.
You know what you are talking about.
I used expensive IR thermometers in my metal processing profession and the emissivity adjustment was very important.
There's going to be some black patches painted on my engine and temperature readings compared to the fixed gauge.
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Old 11-11-2019, 08:33   #11
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Re: Painted engine components... Why?

I kinda assume it was the high temp paint he had. Gold Universal paint from Westerbeke costs a $#@&*@ fortune.
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Old 11-11-2019, 10:19   #12
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Re: Painted engine components... Why?

Its not paint. It's Rust Reformer. It chemically bonds with the iron oxide and makes a paintable surface that will not rust again!
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Old 11-11-2019, 11:16   #13
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Re: Painted engine components... Why?

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Its not paint. It's Rust Reformer. It chemically bonds with the iron oxide and makes a paintable surface that will not rust again!
Rustoleum customer service says it's good up to 200F. I know engine paint is good to 400F or 500F.
Maybe the conversion of the rust to black oxide after applying Rust Reformer has a much higher temperature tolerance.
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Old 11-11-2019, 11:20   #14
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Re: Painted engine components... Why?

Quote:
Originally Posted by StuM View Post
Targets with the correct emissivity for accurate readings with an IR thermometer to monitor engine termperatures?
Oh, that's brilliant. I think you're right given the PO's attention to detail around the engine; that makes sense! Thank you for that information.

I understand why those two dots on the engine block would be ideal targets for measuring internal temperature but do you know why the only other targets were stainless steel components? Is there something inherent to SS itself or is it because they're attached to internals?


Quote:
Originally Posted by captain465 View Post
Why not try to ask the PO?
I wish I could; I don't have contact with the PO.

Quote:
Originally Posted by dennismenace111 View Post
Its not paint. It's Rust Reformer. It chemically bonds with the iron oxide and makes a paintable surface that will not rust again!
Thank you for mentioning that. I'm a new boat owner and still learning things. I looked up Rust Reformer and the first hit brought up:

"Rust-Oleum Rust Reformer instantly bonds with rust and transforms it to a non-rusting, flat-black paintable surface and prevents future rust. It saves you the effort of sanding rust all the way down to bare metal. Instantly converts rust to a protected, paintable surface."

That's pretty exciting to me because while the engine seems fairly pristine given its age, when I examined the underneath, there was a patch of rust. There isn't much room to work on the engine's undersides so I was worried about how to deal with stopping the rust. My first thought was "How am I going to wire that off when I can barely reach under there?!" I think I'll pick up some Rust Reformer and paint that on -- let it take care of things chemically. You've likely saved me hours of toil and frustration. Thanks!
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Old 11-11-2019, 11:24   #15
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Re: Painted engine components... Why?

Quote:
Originally Posted by Poche View Post
Rustoleum customer service says it's good up to 200F. I know engine paint is good to 400F or 500F.
Maybe the conversion of the rust to black oxide after applying Rust Reformer has a much higher temperature tolerance.
So much for an easy solution to the rust. You're right about the 200F and from the technical data sheet, it doesn't seem that restriction changes after the chemical process:
"Do not apply to surfaces, when heated, exceed 200F (93C)."
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