I had the starter on my Honda BF90 replaced because the bendix would spin but not engage. The boat sat for 4 months over the winter. The new starter was used one time and I had the same problem. I called the repair shop and they said I only had a 90 day warranty. I pulled the starter off. The flywheel and new starter bendix have lots of rust https://rustconverters.net/best-rust-removers/ . It seems to me that water is getting in there somehow. I can find limited information on this issue. Any thoughts of what to look for next?