Ocean Alexander ‘64

What area exactly is going yellow? Waterline to rub rail? Above rub rail? Below waterline? Is it yellow even after you do your rinse down?

Most likely tannins from decomposed plants in the waters you cruise. It's annoying but natural. Longer it's left on though the harder it is to remove. It can be found anywhere but most often in back canals and small rivers.

My initial guess too but would like more info to answer based on.

Well it's not oil and mud washes off easier. Tannin stains the bows.. I seem to recall that the New River had a lot of tannin.

How long have you had the boat and how long have you had this problem?

The most common cause is the styrene in the gelcoat being too thick. That goes back obviously to manufacturing but would manifest itself gradually, not on a per trip basis normally. A less common cause is wax on the gelcoat yellowing. However, when it's the gelcoat, it typically happens gradually and not based on a short cruise. That's what makes me not dismiss environmental.

Is it cleaning up when you wash it stringently?

If the gelcoat itself, then many solutions touted online. Most extreme is sanding a layer down. Milder are things like Top Gear and Cleanshine and Starbrite. There's a product called Yellow Treat used for pools and boats.

It's an algicide so if it works, the problem is from the water. I still don't dismiss that possibility as the gelcoat issues are far more common in hot climates than in your area.

I'm assuming the boat hasn't been painted and no gelcoat repair?

I'd try some of the products mentioned and see how they work.

Algae everywhere.

Although less common in the open ocean it's possible, but my bet is it's happening on the way to and from. Watch your bow wave for where it's the color of tea. You could certainly take a water sample and have it analyzed, but my bet is tannin unless there's an old chemical plant where they dump or dumped waste products. Back in my boat yard days we used to acid wash the water lines and bows at haulout. Dk if that's still legal. Common problem.

Paint and gel coat issues wouldn't just show up at the bow wave and waterline nor just after cruising. You're obviously cruising through something that's staining the hull. Do your dock neighbors have similar happening? I'd be careful about regular use of the rusticator. Also most environmentally friendly products will be too mild. Maybe use of a mildly abrasive wax would clean it, but that's a lot of work. Your mention of rust raises the question of are there rotting steal bulkheads or such in the area?

I have run the exact same year and model OA along the coast of CA between Long Beach and S.F. Bay as well as many hours in the Sacramento/San Joaquin River Delta with no issues similar to what you are seeing. I tend to agree with NYCAP on this.

And where is his boat located?