Getting some steam/white smoke

Noticed recently started getting a little heavier steam and I think some white smoke from starboard motor (hard to tell difference). Had a problem with it running a little high on temp last month but flushed sytem, chnged impeller and changed t-stat and temp seems fine now and running good, about 172 at 3000rpm. Been watching the oil and antifreeze and not burning any at all.

Any thoughts?

Exhaust steam is a great early indicator of low raw water flow. By the time the engine temp increases at cruise, the raw water is way down.
I think you still have a raw water flow issue. Describe the age and service history of the U cooler, the heat exchanger and the raw water pump (besides the impellor).

Flushed with muatic acid last year, guessing is original cooler, seems to have good flow through it. Can these be swaped between motors? Two weeks ago U cooler zinc removed and flushed, heat exchanger opened and cleaned tubes, new impeller, new t -stat.

On the coolant side, the big hose that goes from the Hxch to the circulation pump, I noticed the internal spring is not on the bend near the pump but is on the straight part just past it. Where is that sproing supposed to be? Have heard of these collapsing under suction and no way to check it while running.

You can swap the coolers between the engines if needed.

If the oil coolers have been maintained well, the next common restriction point is the exhaust elbows. Like DD said, an increase in 'steam' is usually due to reduced raw water flow into the exhaust system.

For what it's worth, I've never seen a spring that ran the full length of the hose it was supposed to keep from collapsing. Then again, I've never seen the 'supply hose' collapse on a marine engine.