2001 400 Sedan Bridge Planing Problems w/Cat 3126's

I can't speak for a 2001 400db, but I did see the mold my boat came out of in FL. They did not add anything to the bottom of my boat. I was also told that the new model (42DB, that is now the 45DB), started with the exact same mold from the rub rail down, with modification for the integral swim platform. I clean the bottom of my boat on occassion and have not noticed anything at the end of the prop pockets. My boat does not have a lift, but does have the higher hp motors. I monitor the weight of my boat at haul out. It has always been right around 33,500 lbs. with 1/3 fuel and no water (no dinghy). Do you know the weight of your boat? I do have multiple batteries for an inverter, survival suits, life raft, and all of my wife's crap.
 
According to the 2001 spec sheet, the 3126 cats had 340hp... the 6CTA Cummins option had 430hp... That's 180hp difference (for 2 engines) which is pretty big... can't speak to the torque numbers.
 
That 3126-TA motor was generally available in 350HP, 385HP and 420HP versions. I did a decent amount of research a few years back and there are no bottom end 'internal' differences between them. From memory, the 420HP motor will have a larger turbo, governor, injectors and a different head/valve train tune. Maybe some other minor changes, but all in all expensive parts and labor to upgrade from 350 to 420HP. However, there is no iron differences between the 350HP and 385HP motors. It is only a governor and top end retune.....You basically just feed the motor more fuel by advancing the fuel rack at a given throtle position....all done mechanically. Very similar to the new electronic motors that can be retuned with a chip or some software.

I know that the 410DA could be special ordered from the facotry with the 385HP option. It would be my guess, just a guess, that the 400DB may also have had the same special order option from the factory...especially if it was ordered with the lift.

If the motors were to be retuned to 385HP, you could then run a bigger wheel while still reaching rated WOT RPMs. Higher HP, more torque, bigger wheel, more speed, higher fuel burn. Since diesel motors life spans are rated by the amount of fuel burned, there is the potential for shorter life span....however, in all reality the difference isn't that great especially when you consider the feable amount of hours that most of us put on our boat each season...probably 90% of us here put less then 150 hours a year on our diesels each season....nothing when you look at the way they are run in the commercial world.

Anyway....just another option....you did ask for options.....!!!!!
 
Some of what I've read about the 3126's is similar to the 3208's. Better (read: LONGEVITY/more reliable/ fewer issues) at the lower horsepower ratings.
3208's are solid as can be up to 375 hp- not so much at the 425 output.

Just sayin'- be sure to do your due diligence before hopping up the engines.
 
It's Funny you should mention these downward lips at the end of the prop pockets. I was at my boat yesterday to meet a vendor and while waiting i scanned my hull. THe port side has the lift and the starboard side doesnt. Checked an 05 420 next to me and the same thing. I guess searay adds these on as needed. Anyone esle notice this??
 
Very pronounced "curl" at the end of both of mine. Never noticed them until the first time I was underneath cleaning the bottom. I would suppose the purpose is to direct some of the prop thrust somewhat downwards to provide lift to the stern.
 
Sea Ray calls this lip a "hook" and was in fact added to provide more lift at the stern, like trim tabs. Mine was deteriorating and was something my surveyor had never seen (or noticed) before, when I bought my boat in 2008 and hired him to survey it. He probably never noticed before because on my boat this hook was damaged and made it noticeable. Most people wouldn't notice it but if you run your hand at the edge of the prop pocket where it meets the stern, you'll feel it's got this lip.

Last spring I decided to remove both hooks thinking they were added by the previous owner (made out of marine type "bondo"). They were in bad shape anyway with large chunks missing on both port and starboard sides. I DID notice a difference trying to plane the boat after removing them and called Sea ray this October when I pulled the boat. That was when I learned Sea Ray hand fabricated these on every 400DB and got the whole story of why and how it was done. (See my previous explanation from Sea Ray attached below).

I got some prints and tips from the SR engineers and will be reconstructing it soon for the upcoming season. I will be making it somewhat larger (and stronger with fiberglass instead of bondo) than before to add increased lift over the original design and had my idea approved by the SR engineers.

My quote from a previous post:

“By the way....Sea Ray in all their genius manually added (not in the hull molds) what they call a "hook" on the outside edge of the prop pockets to ALL 400 DB's in order to give them more "lift". This obviously was an afterthought by their engineers necessitated by the same problem and (my guess) complaints by original 400 DB owners when the started producing this boat in 95 or 96. It deteriorates after time and needs repair because they crafted it with "bondo." I've spoken with their engineers about this and even they admit "in hind sight, they should have donne it differently." So the planing issue is even known by them. They probably used this same mold on the Dancers and instead of building a mold just for the DB with the "hook" built in (very expensive) they decided to "doctor up'" each and every 400 DB hull that came out of that mold by manually adding this. That pissess me off......”
 
I have the same year boat with the Cummins engines. at 2200 rpms I cruse at 23 to 24 knots. in the slings my boat comes in at 32000 lbs as seen by the travel lift. I have 22x24 props. 22 is the correct diameter for this boat as anything much larger would be very close to the prop pockets. my pockets are straight no lip at the aft end.
I really have no problems with the boat planing off she comes out of the water with little or no effort at around 1600 to 1800 rpm's with little or no tabs. this is with full fuel, water and all our usual crusing crap (which is a lot) and with up to six adults on board.
I don't have the lift on my boat though I would guess that it adds a lot of weight to the ass end.
I do notice that if I run at around 20 to 21 knots then my bow stays up in the air even with full tabs. but when I push the throttles passed 22 knots the bow drops down and I need to back off the tabs.
Usually I get her up on plane then play with the tabs.
Before I bought this boat I looked and tested a 1996 with the 340 Cat's and it realy seemed like a much different boat.
We did not push the boat to full throttle but we were crusing at around 20 knots at 2400. The owner didn't have much stuff on the boat and did not have the lift.
 
Thanks Matt. I'm suprised you don't have the "hook" but maybe it was only added to the Cats. I'm lucky to get 18 knots at 2400.
 
Larry,

Did you get any progress with your planing issue?
 
I have the same problem. But worse, i could only run up to 2500 wot. My speed would only be 17-18 knots. I have a davit and a small dinghy at the back. It eats up
too much diesel at this point. So far after reading this thread, It is normal for this boat with 3216 350 cats?
 
I have a 37'DA w/3116 Cats and my friend has the exact same boat w/gas engines. Mine sits a good 3-31/2 inches lower in the stern than his does. Half tank of fuel, full fresh water tank, early season crusing speed is 22-23 kts at 2450 rpms. Lots of tabs to keep the bow down, no chain on the anchor. I have played with the tabs on extended trips and found that it needs them at least 2/3-3/4 extended at all times. With tabs extended 3/4's I get on plane quickly.
Diesel engines are made to perform best [most efficiently] at about 3/4 max rpms. Running them at wot for breif periods of time will not damage them if all things are correct.
From what I gather from the past posts is that it could be either the props, or tabs are not functioning properly/undersized. Adding more weight to the stern did not do your boat any favors.
 
Thanks Diebroke, however i think we have different hulls? I'm not too familiar with your boat but a 23kt cruise is pretty fast. I took off the davit today. I will try to test her again tomorrow.
 
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