25 Knot Cruise

[billb]

does anyone have a 33 that will cruise easy at 25 knots and have a 30 WOT....how much horsepower do they need honestly and what gear set up...I see a lot on here with 22 or 23 knot cruise with cummins, but to spend that kind of money on a repower, is it going to justify the expense??? Thanks

[dougl33]

Bill, I have 300hp Cummins 6BTA's. Gears are ZF220a 1.53:1. I'm swinging 21x22 3 blades with a #5 (aka med) cup. I cruise at 2400rpms. Depending on load and conditions that gets me 23-24 knots. Top end is 27-29 knots, again depending on load and conditions @ 2900rpms. I think you could get a 25+ knot cruise and 30+ knot top-end using Cummins 370B's or similar hp from Yanmar. I know Brian Davin has 370 Yanmars and he can sometimes cruise at 27 knots.

[franklyprice]

Bill, I have essentially the same setup as Doug but the 330's in a '87 SF. I cruise @24 give or take and it will hit an honest 30 kts top end, a little more without the enclosure. I also still get a little more than 2900 RPM's at WOT so may have a little more if I played with props some more. The difference in handling alone almost makes it worth it but the speed and economy , not to mention the sound of diesels , makes it more than worth it if you can afford it.

[WetProcess]

Replaced 454's in a 33SF with MarinePower 6.2 LS3's (425HP)cruise at 25kt WOT is 32-33kt. Cruise 0.7gpmile WOT-0.5 gpm. Was ablt to keep orig running gear. Eng/Trans combo ~$20K ea (need new trannys as the LS3 not available in counter ROT)

[lobsta1]

Thanks for the update. Your's is the 1st gas B33 that cruises at 25kts. I gather you are happy with the results. Al P.S. Did you do the repower or have a shop do it?

[h2ojst]

Not sure about who was first, but I also cruise (depending on load) at 25 which is about 3500 RPM and top out at 31-32. The diesels certainly take the load much better and obviously better on fuel consumption at the upper end. Fuel injection narrows the gap considerably.

[Rick]

Impressive Joe - please refresh my memory with your power setup. I know you've altered your power curve with the timing, but is that with 454 Gen VI's ? Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

[h2ojst]

Rick, correct on the 3 degree timing advance to bring in the max HP at about 4500 which is my max RPM. I tore down new (in 2005)8.1's which were really just bigger 454's with injection. Probably somewhere in the neighborhood of 500HP. I can't believe it's been almost 14 years and almost 2000 hours later, but they still look new.

[Rick]

Sounds sweet Joe, incredible horsepower too. I'm still working with my year 2000 454's Gen VI's....the injection helps a lot relative to fuel burn but my exhaust manifolds are salt water cooled and need to be pulled and cleaned every two years. PITA ! Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

[captxmas62]

Bill, I am running my newly installed Vortec 454's at 3100 Cruise (23 knots) and 3/4 fuel. I can cruise at 25 knots at 3300, but I see my fuel use go up much quicker. 3100 seems to be her sweet spot and I am fine w/ 23 knots. I have not bought them up to WOT yet, but can hit 29-30 knots consistently at 3800. Just don't have the stones to bring it up any further, mostly because of the money I have wrapped up in these new engines. The engines are 400 hp, roller Cams, HEI Ignition, w/Predator Carbs (700 cfm) and BW 1.91:1 trannys. Props are now 4-Blade 20" x 20" Dynajets w/cup removed. Generator has been removed and new tank has an additional 28 gals added. I will be concentrating on the fuel consumption numbers this coming season once I get the floscans installed, so more to come. I opted out of the fuel injection to keep the engines a bit more simplistic and because I can always get home w/ a carb. Hope this helps a little. I do have a ton of pics, but always run into issues posting them here. All the best, Jim