rslifkin
Guru
- Joined
- Aug 20, 2019
- Messages
- 7,975
- Location
- Rochester, NY
- Vessel Name
- Hour Glass
- Vessel Make
- Chris Craft 381 Catalina
I’m not really thrilled with the 300hp rating. These engines were made for 200-250hp. Higher hp=less life. That being said they are great engines. Marinized variations can vary depending on as others have mentioned exhaust. Get them checked out. If they check good I wouldn’t worry about them to much. Btw you can get the hp reduced pretty cheaply. If the engines have the parts ie crank, rods, and pistons to be set at 300 would pick up a lot of life hours at 250, or even 275. Keep in mind that could require a prop change. If not planning on spinning them up in the very high 2k range you will be fine. I’d shoot for a hull speed rpm around 1,500-1,600 cruising around 2,000 wouldn’t take wot passed 2,500
That seems pretty conservative considering the later 6BTAs came cranked up to 370hp at 3000 rpm on the high end and provided they're not run wide open all the time, they're not known for being time bombs even at that rating. A 300hp rating wouldn't worry me provided continuous cruise power is at a reasonable level. Cummins was willing to offer a medium duty rating (rather than intermittent or high output) up to 250hp at 2600, so I'd figure cruise power on a 300hp should be kept somewhat below that, probably in the 200 - 220hp range for good lifespan.