Okay, as an update to my previous post, I grabbed the Yanmar Service Manual from our boat today. It's the one that covers the 1GM, 2GM, 3GM, and 3HM engines.
According to the engine specs, your 3HM actually turns at a little bit slower speed than our smaller 3GM. Here are the RPM specs:
3GM30F Continuous Duty Rating= 3400 RPM (24 HP)
3GM30F Peak (One-Hour) Rating = 3600 RPM (27HP)
3HM35F Continuous Duty Rating = 3200 RPM (30 HP)
3HM35F Peak (One-Hour) Rating = 3400 RPM (34 HP)
Even still, the 3HM35 engine is designed to run continuously at 3200 rpm. So I would suggest that you experiment by bumping your cruise RPM up to the 2600-2700+ rpm range. The Fuel Consumption tables show that there is very little difference in burn rate between 2200-2800 rpm, virtually none between 2400-2600.
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Pacific Seacraft Crealock 31 #62
NEVER CALLS CRUISINGDAD BACK....CAN"T TAKE THE ACCENT