Nice find with the Trimate IV! For the Striker 4 transducer, you'll wanna mount it where it stays underwater and gets a clean signal, usually on the transom or hull. Since youre not sure how to contact the boat maker, try reaching out to Trimate online or maybe someone here could give a better tipSo I just picked up a restored 1978 Trimate IV and want to add a Garmin Striker 4 and I'm not sure where or how to mount the transducer for best results. Garmin advises checking with the boat manufacturer, but I'm not sure how to do that.