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Old 05-23-2020, 06:24 PM   #1
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OA 440 performance

Does anybody out there have direct knowledge of what kind of fast cruise speed can be expected of an OA 440? Not WOT speed, but sustained cruise speed. The Powerboat Directory says this:

Twin 250hp GM and Cummins engines cruise the 420 or 440 at 15 knots (about 18 knots top), and 350hp or 375hp Cats cruise at 20 knots and reach a top speed of 23Ė24 knots.

Iím looking at a 440 to buy. Iíd like a boat that can do 15 kits sustained. According to the reference above, this should be no problem. However, the selling broker for the boat Iím looking at, which has 315 hp Cummins engines, said that itís really more of a 10-12 it boat.

Are there any 420/440 owners out there who can comment on this?
Thanks,
David
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Old 05-23-2020, 06:32 PM   #2
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I have a 420 with Volvo Penta engines but similar horsepower. I cruise easily at 12-13 knots which feels about the best point at the high end. I donít have a real time fuel monitor (Iím installing one in a month or so) but it seems pretty decent fuel consumption wise.

It can cruise lower but feels less optimal at 9-10 knots. 9 and below also is nice and much less fuel consumption too.
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Old 05-23-2020, 07:12 PM   #3
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A lot of the answer has to do with how much weight has been added to the boat. If the boat is pretty basic than the factory numbers are fairly realistic. If the boat is loaded down with optional equipment then it gets slower. Some boats get so loaded down that they become displacement speeds only.

Sounds like the broker is being honest with you. He is trying to keep your expectations in line with reality.
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Old 05-23-2020, 07:12 PM   #4
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Thanks, Steve. Thant helps.
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Old 05-23-2020, 07:16 PM   #5
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I should have mentioned - I can definitely hit 15 knots but that takes getting higher up on the power band than Iíd like to run with 4000 hours on my engines.

Also similar to Tiltriders note, Iíve eliminated the old flooded battery banks and replaced them with LiFePO4 that saved 600 pounds but there is still more stuff throughout the boat that Iíve put on that has definitely added weight. Having full water and fuel tanks affects things too.
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Old 05-23-2020, 07:18 PM   #6
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Thanks, TR. Other than the usual AC units and a washer/dryer combo, I donít think thereís too much heavy gear on the boat. Oh, just remembered, it does have a Freedom lift on the stern, so that would add some weight.
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Old 05-23-2020, 07:21 PM   #7
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The Powerboat Directory is accurate. Ours has twin 250s....top speed 17-18 kts. It gets over the "hump"/bow wave at 10-11 knots and is solidly on "semi-plane" at 12 knots. Our boat has a fairly heavy center console dingy hanging on a transom mounted Nick Jackson style davit, so it takes some trim tab to get it "out of the hole". Without the dink it pops right up. Fifteen knots cruise is about 140 HP per engine....fuel burn 7.4 GPH per engine. Roughly 1NMPG. For better fuel efficiency, I cruise at 8-9 kts and get 1.8-1.9 NMPG.

Depending on who you ask, the hull is semi planing/displacement or modified planing. In any case it's full in the forward half and has a keel...so it's a bit more draggy at higher speeds, but quite efficient at slow speed and either side of the hump speed. A full planing hull like a Carver would likely do slightly better at 15 and above. I've cruised our boat at 15 with no issues.

The 315 Cummins would be loafing at 15 kts. I looked at the broker's ad, which uses speed data for the twin 250 hulls. I think he's not all that informed or a little careless. Very nice boat, though. It looks like one that was in Sturgeon Bay Wisconsin in the 2006-2007 time frame when we had a slip in the area. The mid-west dealer was there at the time. The boat owner was from Chicago.

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Old 05-23-2020, 07:33 PM   #8
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Steve, thanks the additional info. Iím getting this boat to do the Loop. 85% of the trip will be at displacement speeds. Weíd like to have the option of 15 kts or so to allow us to make the offshore run up the Jersey coast in 1 day, weather permitting; likewise the Gulf crossing and Great Lakes stretches. So we wonít be needing the speed that often. The boat in question was repowered about 10 years ago, now with ~900 hours on the factory reman Cummins. I donít want to be cavalier about it but I think Iíd feel OK running the engines at whatever the manual recommends for maximum sustained speed for the few instances where we might need to. I would hope that would get us 14-15 kts., but maybe not. Thanks for your insight.
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Old 05-23-2020, 07:36 PM   #9
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Rufus, thanks so much! That’s very reassuring.
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Old 05-23-2020, 07:38 PM   #10
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Quote:
Originally Posted by Rufus View Post
The Powerboat Directory is accurate. Ours has twin 250s....top speed 17-18 kts. It gets over the "hump"/bow wave at 10-11 knots and is solidly on "semi-plane" at 12 knots. Our boat has a fairly heavy center console dingy hanging on a transom mounted Nick Jackson style davit, so it takes some trim tab to get it "out of the hole". Without the dink it pops right up. Fifteen knots cruise is about 140 HP per engine....fuel burn 7.4 GPH per engine. Roughly 1NMPG. For better fuel efficiency, I cruise at 8-9 kts and get 1.8-1.9 NMPG.



Depending on who you ask, the hull is semi planing/displacement or modified planing. In any case it's full in the forward half and has a keel...so it's a bit more draggy at higher speeds, but quite efficient at slow speed and either side of the hump speed. A full planing hull like a Carver would likely do slightly better at 15 and above. I've cruised our boat at 15 with no issues.



The 315 Cummins would be loafing at 15 kts.



Attachment 102912


What engines do you have? Maybe I need to be running faster because my fuel economy is not that good around 12-13 so maybe I should be running at 15....
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Old 05-23-2020, 08:10 PM   #11
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Detroits, which are very fuel efficient.
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Old 05-23-2020, 08:21 PM   #12
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Maybe on boats, but on the road not so much

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Originally Posted by Rufus View Post
Detroits, which are very fuel efficient.
When I owned a trucking company I hired a trucking maintenance/management firm. The company tracked data on all new freight liner trucks, to include fuel economy. It had fleet level data on tens of thousands of trucks. In order of most efficient was Cummins, then Cat and only a bit worse Detroitís.
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Old 05-23-2020, 11:11 PM   #13
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Originally Posted by Sevo View Post
Iím looking at a 440 to buy. Iíd like a boat that can do 15 kits sustained. According to the reference above, this should be no problem. However, the selling broker for the boat Iím looking at, which has 315 hp Cummins engines, said that itís really more of a 10-12 it boat.
My OA is a 42 Sedan with Yanmar 440 engines. I cruise normally at 15-18 knots and 21 at WOT. (Which I never do!) I like to keep the rpm around 2500-2700. At idle she 's at 3.8 knots and at trawler speeds 8-9 knots she's really fuel efficient. Here's a couple of photos to see what she's capable of with full fuel and water. (About 38,000 lbs) I would think you should have no problem achieving a 15 knot cruise.
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Old 05-24-2020, 07:30 AM   #14
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Quote:
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When I owned a trucking company I hired a trucking maintenance/management firm. The company tracked data on all new freight liner trucks, to include fuel economy. It had fleet level data on tens of thousands of trucks. In order of most efficient was Cummins, then Cat and only a bit worse Detroit’s.
Sounds like you're referring to 2-stroke Detroits if they were in Freightliners. The OA440 used a compact 4-stroke found in school buses, small dump trucks, and industrial applications. Different animal that's in it's element in a constant rpm application like a boat or pump.
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Old 05-24-2020, 07:49 AM   #15
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Sounds like you're talking about 2-stroke Detroits if they were in Freightliners. The 250 is a compact 4-stroke used mostly in school buses and small dump trucks. Different animal and the marine application a different operating environment...set it and forget it
Rufus, PM sent about your davit. Thanks!
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Old 05-24-2020, 08:17 PM   #16
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Typically

Quote:
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Sounds like you're referring to 2-stroke Detroits if they were in Freightliners. The OA440 used a compact 4-stroke found in school buses, small dump trucks, and industrial applications. Different animal that's in it's element in a constant rpm application like a boat or pump.
Series 60 DD, the most common at the time.
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