Up here in northern NJ, a lot of the late '90 and early 2000 Deep V 25s were rigged with a single 250 2-stroke. Especially the models with 2nd stations since back then, the control options were limited because morse controls were used primarily.
I have a 1999 2530, deep V with full bracket and a single 4 stroke Yamaha 250. I get a pretty steady 1.6 to 1.8 mpg economy throughout most of the RPM ranges. Except for 3,000 to 3,500, just pushing water and the mpg drop down to about 1.0 to 1.2. And when trolling for bass at 1,000 to 1,100 rpm, the economy shoots up over 2.0 mpg.
When I had the 2 stroke OX66, the economy was much lower, closer to a steady average of 1.0 to 1.2 mpg throughout the RPM range. And because of the excessive weight for the engine, it wound up burning a lot of oil closer to a 40:1 ratio. And because of this, it contributed to replacing the O2 sensor every 2 years.
With the single 250, you can go as slow as you can immagine, however, depending on the current, it can be difficult to control at extremely low rpms. With a 17" pitch, running into a headwind or strong current, you regain control at about 1,100 rpms but this may put you faster than you want to go. Not sure how running on a single 150 would act is strong winds or currents.
Since the weight is a little less and distributed a little different on the 2510 vs the 2530, the performance is probably a little different.
I'm sure you can adjust the pitch of your prop, but, I'm not sure how far you're running and how fast you like to run.
As Optimax suggested, this are many performance bulletins on the Yamaha site.
However, if you are looking at older 2 stroke OX66 250s, althought the engines are bullet proof, I would be concerned with the maintenance of the O2 sensor if you would be constantly trolling at low speeds.
Overall, it's a great set up. Unfortunately, I don't know of any for sale in my area at this time.
