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Old 01-29-2019, 01:15 PM   #37
BandB
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City: Fort Lauderdale. Florida, USA
Join Date: Jan 2014
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Quote:
Originally Posted by sunchaser View Post
BB
Questions:
- what engines, model and HP are on your larger vessel
- what is the measured max RPM under load
- have you spent time with Steve Z talking engines
We have various so I'll just give two examples:

44' Riva with twin 800 hp MAN's, i6-800's. Max RPM is 2300 and it runs 42 knots at that. Fast cruise for us is 1950 RPM, 36 knots, 75% load. 80% load would be just a little over 2000 RPM and about 37.2 knots or so.

85' Pacific Mariner with twin 1500 MTU's, 10V2000's. Max RPM is 2450 and 27 knots. Normally we cruise at 1800 to 2000 RPM, 20-23 knots, 50-65% load. 80% load is 2170 RPM and speed is just over 24 knots. Very little gained between 65% load and 80%.

These engines do have electronics reporting load which comes very close to calculations based on fuel consumption.

No, I've never spoken to Steve Z. Most of what little I gather about engines comes from talking to Captains and Engineers we employ and people I've talked to over decades as well as manufacturers recommendations.

Steve Z's 35% load on the above two boats would be about 1275 RPM and 17 knots on the Riva and 1580 RPM and 16 knots on the Pacific Mariner. Interestingly, on the Riva 35% gives about 40% of the speed of WOT, whereas on the PM it gives 59%. We do sometimes run the PM at 35% but never the Riva.

Where it becomes really interesting is looking at jet RIB's, both gas and diesel. I might have to do that later, but back to a meeting for now.
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