Dear Alphard, Thank you for your inquiry regarding Part #1196284 for your Caterpillar 3512C marine engine. Based on the Caterpillar parts information available to us, Part #1196284 is listed as compatible with several 3500-series engines, including the 3512C marine engine. The 1-1/2" specification also matches the listed thread size for this part. However, to confirm compatibility with complete accuracy, we kindly request the full engine serial number and, if available, the arrangement number from the engine data plate. This is important because compatibility may vary depending on the engine arrangement and starter configuration. Once we receive the engine details, we will be happy to verify the correct fitment for you. Best regards,