Cruise RPMs Yanmar 6lpa-stp.

[Legasea]

I purchased a 32+2 with a Yanmar 6LPA – STP 370 hp engine. This engine at wide open throttle will achieve around 3800 RPMs. It likes to cruise around 3100 to 3200 RPMs at about 15 knots. WOT she will hit 20 knots. We put about 100 hours a year on our boat. I’d be interested to know what your cruise RPMs and speed are.

[Tree]

3200-3400 depending on how quick I want to get somewhere really.

[Nancy]

I'm no expert on Yanmar engines, but I'm confused by your model number.
I thought 6LPA-STP was a 315 hp engine. But yours is 370?
We have a 2005 35CB with 6LYA-STP 370 engine.

Rated WOT for the 6LYA-STP is 3300 rpm.
We like our diesel engines to be propped to achieve 100-150 rpm over rated.

In any case, is your tachometer accurate? Ours was way off because the dip switches were set incorrectly. Probably had been for years. We replaced it anyway because it was unreadable due to a clouded lens. The new digital tach is a big improvement.

Conventional wisdom is that diesel engines should cruise at 80% of rated WOT. My understanding is that the Yanmars will live longer if underpropped. If your engine is rated for 3800, and that's what you're getting, I'd be inclined to get the prop tuned and also back off the R's a little.