Unequal size exhaust hose and thru hull connection

[Kapow13]

After a repower the new wet exhaust hose has an ID of 2". The existing bronze exhaust thru-hull which is fiberglassed into the transom has a barb OD of 1.75".

Want to avoid replacing the quality bronze thru-hull. Anyone know a secure method to connect the two? Or a supplier of bronze or composite reducers in these diameters?

[Toccata]

You may not want to, but I reckon you have to (replace it). You will probably have too much back pressure.
It is possible to connect those two sizes, plastic (exhaust will be quite cool by the time it's at the transom) or grp (vinyl ester resin) fittings or weld two SS hose tails together.
Set it up and then measure your back pressure, make sure it's within specs.