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

fwebster said:
Larry,

There don't appear to be any mechanical problems with the engines since they both turn up 2800 rpm. You hardly ever see fuel delivery, turbo, etc. problems affect both engines at the same time and in the same way, and you did not indicate that in your post.

The bottom isn't fouled or you would not see 2800 rpm.

Your boat's previous owner's re-ptiching the original props is quite normal since Sea Ray tweaks the wheels with a very light load. At some point most mid 90's-early 2000's owners did the same thing to get the engines to turn rated rpms without overloading. "Shaving", whatever that is, or messing with pitch or cup in this case serves no purpose since the engines are performing as they should.

Most likely, you have a normal 400DB, and based on your comments, you may have expected it to perform like a Sundancer, which isn't going to happen. The 400DB is a big, stern heavy boat. Compounding that is the hydraulic swim platform which adds even more weight well aft of the COG. It is what it is and, short of moving the COG and using a lot of tab, there isn't much you can do about it other than adapt to a stern low attitude and speeds of about 20 kts.

One of the things all the 400DB owners in our area have done is to go to an all chain anchor rode to put several hundred pounds right on the nose of the boat. It helps, but not as much as you probably want.

Sorry, but I don't have any ideas that will add to the positive side of the equation........
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We have seen the same thing with the all chain anchor rode. The boat runs better and of course the anchor works better too. It sounds to me like everything else is ok on this boat.
 
Nice post, Dom!

You should get one of those little wrenchy thingies next to your name for that.
 
Frank-
All kidding aside, what do you mean by "ownership thresold" in this post?

fwebster said:
Read more carefully Tim.............I said "Based on his comments".........he may be expecting the 400DB to perform like a DA, but it isn't going to happen. And, all my comments are based on the 400DB.

For my taste, the 400DB is a good boat, but she represents the ownership threshold for Sea Rays for DB's due to the whole weight and balance thing. As the boats get bigger, they handle and perform better. Other than the diesel 370DB, those under 40 ft tend to be stern heavy and slow. If you like the 44DB, go run a 480 sometime and the old 6V92 powered 550DB is a tremendous boat.

I'm just sayin.....................
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It's teetering right on the pokey point.
 
Is the discussion here about figuring out RPM's and diagnosing potential engine problems even relative? The Original poster said his boat turns up 2800 rpm @ WOT, as he loads it. There doesn't seem to me to be any engine problem here........its hard to fix stuff that ain't broke.


Tim,
"Ownership threshold" in this context is nothing more that the point at which I'd consider owning a Sea Ray sedan bridge. Said another way, I'm not interested in owning DB's smaller than the 400DB so it is my ownership threshold on this style boat. And, it has nothing to do with looks, style, 2-story or one, greenhouse or not, but is more about a boat doing when it is supposed to do in a safe, comfortable and efficient manner.
 
lkrompier said:
I have a 2001 400 Sedan Bridge w/Cat 3126's and have planing problems and speed problems since buying the boat in 2008. My avg speed at 2400 rpm's is a pitiful 19-20mph and planing is difficult without going over the safe 2400 rpm. The boat is not overly weighed down. I also have a hydraulic swim platform. I've heard this boat has problems getting out of the hole with these Cat motors. Props are supposed to be 22 x 24 but the previous owner had the pitch changed and they are now 22 x 23. The RPM's are right on at 2800 wot, where they should be. Anyone having this problem or resolutions?

Thanks, Larry
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I'm by no means a prop expert.

However, I have seen it printed many times by such experts that "motors don't move boats....props move boats"

Being properly propped is key.

The three main components to proper propping are diameter, pitch and cup. There are many others such as number of blades, blade surface area, prop metalugy, etc. Unlimited combinations of each can get your motors to rated WOT.
That won't necessarily mean that the boat is optimally propped for acceptable performance. Time to plane and reasonable cruising speed (at recommened motor RPMs) are two other very important criteria to consider in the equation.

You may want to consider visiting a reputable prop shop and having a discussion with the technician. There may be a workable, albiet costly, solution to your two concerns. You may have to first decide if quicker planning is more important then slower cruising. IMHO, 16-17 knots IS very slow cruising.
 
Excellent advice above.
While there's apparently no issues with the mechanicals, and the boat IS propped "correctly" in terms of not overloading the engines- it doesn't necessarily mean it's the "optimal" prop.
For example, too little diameter might translate to excessive slip. Is the 22" dia. Sea Ray spec? I would take the advice given above and contact a reputable prop shop- like Admiral or General Propeller. They have computer programs that are pretty amazing at determining optimal prop configurations when given the specifics of your vessel. Part of this process should involve pulling the props and sending them out to confirm the 22 x 23 that's stamped on them is really what they are. I've seen plenty of mistakes...
 
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Thanks for all this info. I'm already all-chain. What about putting on larger tabs to bring the bow down and get on plane?
 
If you have the room on the transom, can you extend the width of your tabs by six inches? If so, you can do what I did on the previous boat. I contacted Bennett and got them to send the fixed slide part for a 30" pair of tabs (I had 24"). I then had a stainless fabricator weld a 5 1/2" width extension to the old trim tabs and reinstalled them in the new slides. I had to use different holes for the mounts but could keep the piston in the same location. I just centered the larger tab and slide, 3 inches on either side.

The reason for all this was the fact that I added a large epoxied aluminum swim platform extension with a more substantial dinghy. The larger tabs worked well going up just the one size and allowed me to get on plane better than before. In fact I used one degree less tab (as per the Trimdicators) when on plane due to the larger wetted running surface.

Do you think that might help? This was an express boat. Maybe the height of a sedan bridge might make it too tender in its handling???
 
The RPM's are correct and all other variables like clean bottom are also ok. You are right that the boat is heavily weighted and probably not tested that way by Sea Ray. I usually run with full fuel and water and the hydraulic platform with the dinghy and motor add weight. So........I can not mess with the prop because it will change the rpm's and I'm stuck with a boat that won't get on plane unless I decide to run it at 2600 rpm's (which is where it gets up) but I can't in fear of damaging the motors at that high a constant rpm? I'm really considering bigger tabs. Anyone have a though? 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...... But back to my first sentence, any thoughts on larger tabs? After all, this goes with the theory of more lift just like the "hook" Sea Ray added to the pockets.

Larry
 
As I suggested before, larger tabs should bring the bow down. It's physics...
The question is whether the added drag will offset what is gained by the improved running attitude of the hull.
Trim tab "size" is measured in square inches- not length or width. So even if you're using the full length from tunnel to chine, it may be possible to add wider tabs (say, from 12" to 18"). This may mean re-configuring the hydraulic rams as well, which may or may not work depending on the clearance under your platform.

The bottom line is that no one here would have the particular expertise to provide a definitive answer on whether this is a worthwhile pursuit with your particular hull.

Bennett Marine has tech support and customer service second to none. Suggest you call them at (954) 427-1400 to discuss your particular application.
 
I personally think that boat is too small for a hydraulic lift. Was that a Sea Ray option? I didn't think they put a lift on that boat for those years.... was this added after the sale? A hydraulic lift and platform adds over 1000 pounds to the backend of a boat BEFORE you put a dinghy on it.
 
I know of two 400 db's with lifts. They both sit stern low and had to have the bottom paint raised. The boats also cruise at 18 - 19 knots and use a lot of tab when running. I would not put a lift on my boat.
 
My buddy has a 2003 400DB with a Florida Bow Thrusters lift (aftermarket). He carries a 600 lb. dinghy on the lift. His boat has the 480CEs and cruises at 22-24 knots with little/no tab. His boat does take longer to get out of the water than mine; and he did have to raise the bottom paint; and his generator exhaust gurgles like crazy (gurgle, gurgle!:wow:) because it is right at the waterline. But other than that, it's fine.

I'm sorry to say that this boat with a lift and with 350HP engines, might just be a tad underpowered.
 
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That's great information and was exactly what I was thinking about. THANKS!
 
The platform was added after production just prior to delivery, but is the same exact platform that WAS a factory option on the 400 in 2001.
 
Any of you 400 DB owners (or anyone) familiar with the "hook" I mentioned earlier?
 
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