Cleaning surface rust off a Diesel

[zenith_adelaide]

My newly purchased boat has a very functional Leyland Thornycroft 230 Diesel. Works well so far but it looks terrible. Just lots of surface rust.
I would like to clean it and make it look better without having to take it our or dismantle it.
What can I do to remove the surface rust well enough to be able to apply some paint to the surfaces?
I've attached a couple of photos as examples hopefully they attach properly. There is a bilge directly below the engine so any chemicals etc could be collected although hoping to damage the bilge pump in any way.
Looking forward to some proven suggestions.

[RaymondR]

Coro Dip from Liquid Engineering in Perth will get it off. I used to mix 1L of Coro Dip with 5L of water in the bilge of my steel boat and pump it around with a small 12 V submersible pump with an occasional brush with a wire brush. Took it back to bare metal in no time.

[a64pilot]

I wire brush off loose rust and treat with a rust killer that chemically changes the rust and makes it inert, then brush paint.
Although I’ve not had to deal with rust that bad before.

[Cheechako]

Yeah, that looks bad. I think you re going to have to do most of it manually first or any rust dissolvers will be blocked by the loose debris. Scrape and wire brush. There are various wire brush attachments for a drill motor that will help to get in tight places. Once you have done everything you can that way, I would paint on thick some Naval Jelly rust dissolver, let it sit an hour or so, then hose it off into the bilge. A cloth like part of an old sheet to catch debris under the engine but let the water through would be nice.
Then leave the engine compartment open, maybe with a space heater or large light bulb and let it dry. Repaint soon.

[Sailing August]

VHT SP229 Rust Converter works great.
$9.50 USD per spray can on AMAZON.com
Spray it on and let sit. Use a wire brush to clean it off. A little brake cleaner
or denatured alcohol and you are ready to paint

[dennismenace111]

If it ain't broke, don't fix it. ! You'll be happier in the long run!

[mikereed100]

The rust may be the least of your worries. Those fuel lines and that wiring are begging to be replaced. Look around the engine compartment and try to figure out how the engine got that rusty to begin with. At the very least, it suggests a PO who did not take maintenance seriously. I would remove all the fuel lines and hoses, wire brush as suggested previously, and coat with phosphoric acid or the equivalent. Then paint and replace all those vinyl hoses with proper fuel lines. Wouldn't hurt to check everything else while you are at it.

[Lepke]

I use Archoil 5100. It dissolves rust but doesn't harm base metal. It comes as a concentrate that dilutes 16:1. It doesn't harm paint or other metals. Available online at archoil.com
I've brushed, sprayed and submerged metal with excellent results. For fun, I found a lineman & needle nose pliers in my bilge (salt water) that had been there for years. Soaking overnight, all the rust was gone and the pliers worked smoothly.

[mikereed100]

Originally Posted by zenith_adelaide

My newly purchased boat has a very functional Leyland Thornycroft 230 Diesel. Works well so far but it looks terrible. Just lots of surface rust.

Maybe, but that much rust could be indicative of years of neglect. Are those fuel lines really vinyl? Duct taped wiring? Anyhow, you may want to remove all the fuel lines, wiring and hoses prior to addressing the rust. Then wire brush and treat with phosphoric acid or the equivalent before painting. Then you can replace the fuel lines with proper hose and take a close look at everything else.

[waterman46]

To get in the tight spaces a Dremel grinder with various wirebrush attachments is useful. First degrease using carb cleaner and paper towels. It may take several cans. Then wire brush. After grinding and brushing I used carb cleaner then acetone in a squirt bottle with plenty of paper towels to degrease and rinse away rust. Open all ports and have a fan blowing in outside air when doing this, and wear a fume type respirator, and for safety turn off all electric switches and disconnect shore power. After the acetone rinse you can spray paint engine primer then your favorite decorator color engine paint.

[jharding]

I used a water pik to clean in tight places before I painted, it worked well with out making to much of a mess. Cleaning and painting is very good, any time you have a small leak you can see it before it becomes a bigger problem. I used a good rust inhibiting primer then engine paint.

[Digdug]

You want to clean it with brake clean, a wire brush, lots of rags. Wear a mask and gloves. Then use ospho 605. This is a specific chemical to neutralize rust before painting. You just paint it on and let it dry overnight. Then you can apply some paint, like rustoleum semi gloss white painter’s touch.

[Capt. Rehab]

there are many rust removers or converters but all benefit from a thorough degreasing First....Dont use wire brushes made of steel they will broadcast micro particles throughout bilge which Will rust. Certain Rust Removers convert leaving stable coating for primer others strip to clean metal Some of these disburb existing paint some do not. Its a foul job but oh so worth it!

[zengirl]

Ospho 605 Metal Treatment
by Ospho
4.6 out of 5 stars 187 customer reviews | 59 answered questions
Amazon's
Choice
for "ospho"
Price: $18.98 Free Shipping for Prime Members

I just did my engine mounts with this and was recommended to me by an old salt that has worked on boats for 50yrs. I scraped and sanded and then applied this. What I liked is it didn't coat bolts etc like paint would so won't interfere with future removal of bolts.

[Hyrdflyr]

Ospho is the best and 1/5th the price of the aerosol cans if you take the quantity into account.



So, wire brush, then wash with non-flamable brake cleaner to get any grease or oil off, then ospho, then wash with clean water. If it does not turn all the remaining rust black, then redo. If it is still brown, then it is greasy or oily, so clean again and ospho againthen paint with a good primer, and then epoxy paint.


Be thorough, don't be in a hurry and it will last for many years.


Cheers, John