300 HP vs 350 HP 3116's in a 400 Sundancer?

[oarwhat]

A friend is looking at a late 90's 400 Sundancer with 300 HP 3116's. Anyone on here own one or have real life experience with them? Do they seem under powered, cruising speed, fuel burn, etc.etc. Does it lower the value of the boat? Thanks in advance Randy

 

[becnme]

I had a 97 400 with 300 HP 3116's. I heard a lot of negative comments on it being under powered. I loved that boat. Mid 20's (mph) cruise 21-22 gph fuel burn. Unless you need more speed and fuel burn don't be afraid of that boat.

 

[fwebster]

I've run both versions and for normal day to day operation I wouldn't turn around for the difference between them in how the 400 handles. If you plan to run at or near rated rpms all the time, then opt for the 350 hp versions. However, most 3116/3126 owners tend to find a sweet spot down around 2200-2250 rpm where both versions will just loaf along and burn about 18 gph.

 

[oarwhat]

Ok thanks for the replies. We met the previous owner and he said the boats cruises at 22 knots at 2200 RPMS. That sounds great but he said it burns 35 gallons an hour!!! That's no where near the 18 to 22 gph you guys are talking about. What's the deal?? Thanks again

 

[Z-Worthy]

Either he's mistaken, or he has something very wrong with that boat. I never really did any calculations to get exact numbers, but I'm nowhere near 35gph. Just going off rough estimates and ballpark figures I'm burning somewhere between 20-25gph, at the most. Is he running his generator for extended periods on the hook or at the dock and not counting that into his fuel burn numbers?

 

[oarwhat]

It sure seemed way to high to me.

 

[FastMarkA]

The generator on those boats burn 1-2 gallons/hour max. On my 450DA with 3126/420hp, I get around 23gph at 2250...35 gallons is either incorrect, or something is egregiously wrong...

 

[rondds]

sounds like gas engine numbers.

 

[barlow]

My 630 NM delivery trip averaged 22.8 US Gals/hour of run time at 2200-2300 rpm.

 

[RollerCoastr]

Without meters, everything is just varying degrees of guessing. My meters tell me that my gassers burn from 28-38 gph at cruise, depending on speed and load etc. If I calculate by my hour meters and long-term fuel burn, it never hits 20!

I'd chalk a diesel 400 burning 35 GPH to a really bad guess.

 

[Riptide III]

Without meters, everything is just varying degrees of guessing. My meters tell me that my gassers burn from 28-38 gph at cruise, depending on speed and load etc. If I calculate by my hour meters and long-term fuel burn, it never hits 20!

I'd chalk a diesel 400 burning 35 GPH to a really bad guess.

I burn 21gph. At 2200. Not a guess. Just math.

 

[rondds]

Long term numbers will ALWAYS be better than the numbers at cruising speed only. We dot realize how much time we spend lolly gagging around at hull speed. At 3300 rpm on my current boat the gph is around 30. For a season, I'm around 23. All the "no wakes" around here are the cause.

 

[RollerCoastr]

Yep. It's not just the throttle position either. Engines spinning props to push a hull through water have variables in the fuel burn - that's just an unavoidable fact. A wristwatch and the readout of the pump at a fuel pier can help us find a reliable average, but without more data, that's a GUESS of the fuel burn at any given moment.

I'm not saying they're not GOOD guesses or extremely accurate averages. I've done it myself with meticulous logs and decades of boating, but after installing meters, I had several "huh" moments.

As far as the math goes, you can't put a variable into the formula and produce a constant in the result.

 

[fwebster]

Caterpillar does a great job of providing reliable numbers for fuel burn on their engines. I have the Marine Propulsion data card in front of me and t he 300 hp 3116 burns 9.7 gph /engine at 2400 rpm rated cruise rpms; the 350hp 3116 burns 11.3gph/engine at 2400 rpm. I have verified the numbers many times on my boat 350hp/3116's (over 1500 hours and 17 years) as well as others with both 300 and 350 hp engines and the total consumption is never off by more than .2 gph.

However, the gotcha here is that the engines must not be over or underloaded, they must be propped to yield 2800 rom at WOT, for the load on the boat.

In the real world, most 3116 owners choose to run the engines down around 22-2300 rpm which is a sweet spot for these engines. If for no other reason than the fact that the turbo noise is almost eliminated below 2300. With 350 hp engines, that get the fuel consumption down to about 18-19.0 gph total for both engines. So who ever said these engine burn 35 gph is wrong....or there is something really wrong with their boat.

 

[oarwhat]

Thanks for all the responses guys!!! I'm not receiving emails even though I'm subscribed to this thread. Engine survey and sea trial is next Wednesday!!!