My first suggestion would be to do nothing. A 7 year old OMC 175 has many years of trustworthy service left in it. You're talking about spending $12-15,000 to re-power; you can buy a lot of gas and oil for that kind of money.
However, if you are hell bent on re-powering I would go with the
Evinrude 200.
The Evinrude 200/225/250 engines all use the same 3.3 liter block. The 200 gets you the bigger displacement engine without the additional expense of the 225. The performance difference between the two would be negligible on your boat, maybe 1.5 MPH at WOT.
If you want, you can use your existing OMC controls with the new Evinrude, furthering your savings. If you decide to upgrade your controls and gauges, you will still be money ahead versus a Yamaha or Suzuki 4 stroke.
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