To ensure you’re replacing your engine correctly, make sure to read our guide below with relevant catalogs to find the right engine replacement. There are many variables that come into play when replacing an existing engine with a new one (shaft extension, mounting base, overall fit, etc.). The most common question that we get asked is :- what new Briggs & Stratton engine should i replace my old model with.? Determining which model is the correct replacement, following our guidelines below will help narrow down what to look for in your replacement options.