Re: 235 johnson powerhead
You are pretty much stuck with the 235 powerhead unless you change the midsection exhaust adapter. Currently yours is setup for any bubble back 235 engine. The loopers won't fit nor will the flatback crossflows. Likely you can find a 150/175/200 crossflow midsection adapter in a salvage yard and swap it out. Once changed, you would be able to use any of these crossflow flatback engines. These flatbacks were made by the thousands and used/rebuilt engines are more plentiful than the 235 version. If you swap for a flatback crossflow, all of your components will work, like the ignition system, starter, etc. The 235's used the larger 1 3/8" carbs which may be too much fuel/airflow for the flatbacks. I'd look to get the specific matched set of carbs with any new powerhead to save time fiddling trying to make the big-throat carbs work. You did not say what year this is, so check the exhaust cover on any replacement block. You may need the special holes for mounting the later model power trim box.
