Quick asistance w/C30 fuel economy. Must accept/reject asap

[serpa4]

Good evening. I was out on a 2015 C30 today with my surveyor.
The survey is on a 2015 C30 with the 435hp, not 370hp. It has about 78 hours on the engine.
They surveyor said it started and ran great, no smoke, no leak, ran consistently at 185 deg. It was in Florida in the bay near Tampa. Calm water, no current, and almost no wind. We had 4 adults, 150 gallons of fuel, and about 60 gallons of water. It was not packed for a trip, so other than fuel/water/passengers, was relatively empty. It has bottom paint in decent condition. It is the luxury package with gen and AC. No dinghy. Trim tabs fully deployed to get nose down. Trimming up raised the bow, but not much effect on the speed or economy.
I was hoping for a cruise of about 17-20kts at about 1.5 to 1.6 statue MPG. I hope to make a few hops out to the islands of the Bahamas and am concerned about distance on a tank of fuel, jumping only during daylight, and having a 10-12% safety reserve of fuel left.
Reviews say about 1.8 nmpg or so.
Some members say about 1.5 to 1.8 nmpg.
A couple months ago, I test drove a 2020 435hp C30 with 160 gallons of fuel, 4 adults, and at a about 800ft altitude, fresh water lake.
It consumed 14-15gph at 20.3 kts. It was not WOT, I did not get the RPM.

Today:
1400 rpm 1.6gph 6.8kts
1800 rpm 4.3gph 8kts
1900 rpm 5.1 gph 8.2kts
2800 rpm 14 gph 14kts
3000 rpm 15.8 gph 16kts
3000 rpm 16.0gph 16kts
3450 rpm 22 gph 20kts
3500 rpm wot 22.1 gph 21 kts

This seems to be off. About 1 nmpg. And WOT is 21kts.
Does this seem right?
If so, then at cruise I'm about 1nmpg x 162 usable gallons (180galx90%) for a range of 162 nautical miles on a tank.

If I start looking at the C302 with .9 nmpg x 270 usable gallons (300gal x 90%) for a range of 243 nautical miles on a tank.
The range of a C302 seems better than the one I drove today.
However, the 2020 C30 was at 1.35nmpg is about 218 nautical miles range on a tank.
Am I looking at the right boat, C30 or should I be looking at a C302?
Is the 2015 I drove today fall short of what it should do or are my expectations out of line.
Many reviews say 1.6nmpg at about 16-18 kts. is about right for a C30.

I need to know if I should accept the boat and buy it, or get my deposit back.
At 162 nautical miles, it WILL NOT meet MY requirements for distance between stops if I island hop in the Bahamas once or twice a year. This would be a deal breaker for me.

 

[Capt’nKarl]

IMO you have the numbers. Seems to me this boat does not meet your stated requirements. Don’t let your desire override your logic. Wait and get the boat that meets your needs.
Karl

 

[jlhowland]

The best info you have says this boat won't do what you want. If you want to island hop in a Cutwater, the 302 is your boat. Bigger tank and two engines.

 

[serpa4]

The best info you have says this boat won't do what you want. If you want to island hop in a Cutwater, the 302 is your boat. Bigger tank and two engines.

Yep, started looking at 302.

 

[daveme]

Sorry to be seeing your post just now. I have a 2014 435 CW 30 Command Bridge. Top speed for me is 21 knots, maybe 22 if clean.

Dave

 

[JamesC28]

I have the C28, so can't validate your numbers. I cruise at 17-18 kts and get 1.7-1.8 nm/gal. That's at 3000rpms.

But, what I have noticed is that these boats are very sensitive to weight and the condition of the bottom as well as sea state. With 2-3 people and a sort of clean bottom my WOT is 3340-3350 and maybe 22kts. I took my boat out alone with very little fuel, no water and flat calm conditions and a freshly cleaned bottom and saw 3450 rpms and 26kts. Going downwind or down current, I can pick up 10% easily. Best of luck.

 

[serpa4]

Sorry to be seeing your post just now. I have a 2014 435 CW 30 Command Bridge. Top speed for me is 21 knots, maybe 22 if clean.

Dave

Thanks for the input. I've talked to another member with very similar conditions/fuel, etc. and they are getting:
2015 CW 30S with the 435 does around 16.5 Gal/h at 20k at 3220 RPM.
He also reports: With only two adults plus full fuel etc it will do 20kn at around 3000 rpm at around 15 gal/hr.

His 2015 is still much better than my almost purchased 2015 at 22gph/21kts at 3600 rpm.
Maybe the one I looked at was just dud.

I'll keep looking.

 

[serpa4]

My wife wants to look at the Ranger R31. But at 15kts, it is slower and also worse fuel economy (GPH) than the CW. If I go much slower, I should have kept my Lagoon 400 catamaran with twin 40hp. It could to 7-8 kts with really great MPG. Demast it, remove running and standing rigging and call it good.
But, at 25ft wide, wont tow well behind my truck 😳

 

[bill46]

C30 fuel economy seems in line with my R31. Basically same from 2800 to WOT. C is of course faster than R with larger engine.

 

[nicozimmerman]

I have a bottom painted 435hp 2015 CB 30 and with 2 adults and 2 kids, 120 lb dinghy and outboard, relatively full fuel, water and gear for a weekend trip I get about 17 kts and 1 nmpg at 3200 rpm.


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[FlyMeAway]

78 hours on a 5-6 year old boat?

Possible poor break-in is affecting fuel economy. Do folks know if these diesels don’t hit full economy until 100+ hours and proper break-in? That’s true of some diesels I don’t know if it’s true of these (I’ve owned several new diesel cars and trucks and they all had steadily improving fuel economy through the first 5,000 miles).