I get a lot of hard water spots on my Mercury motor.  I have used hydrochloric acid on it with great results but feel that it will ultimately damage the cowling.  What else can I use?

Vinegar - otherwise known as Acetic Acid...just a lot milder acid than hydrochloric.

I've been using Boat Bling Hot Sauce since I purchased the Pro-V Bass. 

It's a vinegar-based product.

Having a Black boat, I buy it by the gallon.

Totally gets the job done for me on the hull, motor & Talons.

Basically safe on any hard or painted surface. 

https://blingsauce.com/products/hot-sauce?variant=15995706015778&gad_source=5&gad_campaignid=22870656431&gclid=EAIaIQobChMI_-OOg4j5jwMVvDcIBR1_GDdjEAQYASABEgLgKvD_BwE

 

😎

A-Jay

https://youtu.be/qwd7bFNTKwo?feature=shared&t=981

 

The straight vinegar was amazing.  Do I need to rinse it off after I wipe it down?

Yes, it's an acid and eventually eat what ever you apply it to.

Also, make sure you put a good protective coat of something on your cowl after using any harsh cleaner.  Ceramic, wax, bass boat saver, bling, hot sauce, whatever you choose.  You will find you may not need the harsh help.  

I use a polymer sealant on everything.  

6 hours ago, Jig Man said:

I use a polymer sealant on everything.  

Not trying to be a smart arse, but if you are using sealant and it’s not stopping water spots, I’d switch products.  Is there a problem with the water you fish?  High calcium? 

Our lakes are very rocky with the dominant rock being limestone.

^ That'd do it. Limestone in water increases the PH - makes it more alkaline - and that's where the spots come from. Limestone is Calcium-Carbonate.

 

FYI: TUMS is also Calcium-Carbonate - helps reduce stomach acid.

This is just one of the hundreds of rocky banks in one small lake which I fish.  The main lake is called Table Rock for a good reason.

 

On 9/28/2025 at 8:27 AM, Jig Man said:

This is just one of the hundreds of rocky banks in one small lake which I fish.  The main lake is called Table Rock for a good reason.

 

Good ol SW MO lakes.  All rock.  Love that lake.  It might be that pic but water looks dirtier then its normal clear.

Mike all of our lakes have been that way since mid spring.  Even my clear water at Stockton only has a couple of feet of visibility.  But that hasn’t kept the fish from biting.

7 minutes ago, Jig Man said:

Mike all of our lakes have been that way since mid spring.  Even my clear water at Stockton only has a couple of feet of visibility.  But that hasn’t kept the fish from biting.

 

What causes clarity issues where you are at?

 

Agriculture is our biggest problem here in Iowa I would guess. Fertilizer and run off.

 

But looking at Table Rock and similar places down where you are, agriculture doesn't seem to be common. Seems to be mostly forest/hills. Residential areas of course also.

Lots of spring flooding is what I think this year.

I used Ducky water spot remover for decades on my/Black Merc cowlings.

There was a guy who would wipe down cowling at tournaments and hand out small spray bottles of Ducky, that is how I got started using it.

Tom

^ Ducky contains Citric Acid - another mild acid that will remove alkaline deposits.

On 9/27/2025 at 8:44 AM, A-Jay said:

I've been using Boat Bling Hot Sauce since I purchased the Pro-V Bass. 

It's a vinegar-based product.

Having a Black boat, I buy it by the gallon.

Totally gets the job done for me on the hull, motor & Talons.

Basically safe on any hard or painted surface. 

I use this stuff too. Works great. Spray on, wipe off. Easy peasy.

 

I also use the vinyl sauce frequently on my seats, and the condition sauce twice a year.

^ This one has Acetic Acid (Vinegar) as one of it's ingredients.

 

Notice a pattern? Mild acid to remove water spots caused by alkaline deposits....

I haven’t been anywhere to buy Ajays hot sauce.  But after I rinsed the vinegar off good I put a fersh coat of Bow to Stern on the motor.  I took it to Stockton lake and spent time in both major tributaries (Big Sac and Little Sac).  When I got home there was a little spotting.  I sprayed it with my homemade screen cleaner and dried it.  The spots are gone.

 

Thanks for the info.

On 9/27/2025 at 8:33 AM, MN Fisher said:

Vinegar - otherwise known as Acetic Acid...just a lot milder acid than hydrochloric.

What Ken said. I’ve always kept a spray bottle with approximately 75% vinegar 25% water. Removes water stains easily and it’s very cost effective.

Do you have to rinse it off?

^ I would - even weak acids will affect the finish...but just splash some clean water on it and wipe it and you should be good.

I kept a water stray bottle and clean rag to wipe the entire boat and engine down after spraying hard water spots before leaving the lake. Easy to keep the engine and boat clean before it dries.

Tom

 

19 minutes ago, WRB-2.0 said:

I kept a water stray bottle and clean rag to wipe the entire boat and engine down after spraying hard water spots before leaving the lake. Easy to keep the engine and boat clean before it dries.

Tom

 

I agree, Tom.

But we don't all have the benefit of sunny California weather all year.

Rain, fog, snow, dirt & gravel roads and let's not forget all the bugs on the ride to & from the lake.

It's like a battleground up here. 

😎

A-Jay