Firstly I should say I'm new to these threads and have found them to be an astounding information resorce. Thank you all for the contributions.I run a pair of 350's in an older Searay. I'm wondering about a safe high end (revs) for an extended cruise of 4 or more hours. My concern is more about long term life of the engine. The Searay specs suggest that I prop my boat to allow a WOT of 4200.