410 Performance problem

Dkruid 410

New Member
Mar 24, 2008
30
Deltona, FL
Any help would be appreciated. I currently have a 2003 410 Sundancer that I purchased about 3 months ago. I am having a problem reaching the proper rpm on the 3126 TA diesel motors. My WOT is 2500 RPM and all the spec I have read and the CAT mechanic says it should be at 2800 at WOT. The CAT guys say everything on the motors are perfect but his concern is that the boost from the turbo is not going down once the boat reaches WOT and gets on plane. I have swithced the props with new ones I got with the boat which are the same that I took off 22X24 Nibral 4 blade. Another 410 owner stated that he is going to 22X22 and that this helped his RPM reach the 2800. My concern is also the speed of the boat. All test I have found have shown 32-34 MPH with full fuel water and 3 people on board. My old props have been sent to a prop shop and they say they are going to make them 21.75 X 21.75. Am I going to far with them and will I lose all of my top end speed. Right know with the motors only getting 2500 RPM I am running about 28 MPH.
Sorry I posted this thread twice. I first put it in general and then seen Sport Yachts.
 
Don't be working on but one variable at a time..........

First check the condition of the boat bottom. These engines and this hull are sensitive to bottom growth and slime. It doesn't take that much of a build up to clip 300 rpm off the WOT.

Since you already have Caterpillar involved, they have the correct test gear to determine if the engines are performing and it the turbochargers are operating as they should. One thing to check is to see if there is a build up in the aftercoolers. If you or a previous owner has been using a multi viscosity oil, like a 15W40, then it is possible and even likely that your aftercoolers are clogged with residue from the viscosity improving additives in the oil.

From here is it all about matching the prop to your nrormal loads. Sea Ray does a good job of matching the props to the boats so you should not cut any outside diameter off the wheels. They tweak the props at the factory with a very light load and we owners usually load up a boat with all manner of junk. It is not unusual to have a little cup or pitch removed from the factory props.

Whatever you do, do not run the boat for extended periods at WOT or even at rated cruise rpms until you get your WOT rpms back up to 2800. Caterpillar is specific in determining cruise rpms.....85% of WOT. That means if you are propped right, WOT is 2800 RPM and cruise RPM is 2400. But if you can only turn 2500RPM at WOT, then your cruise RPMs is 85% of 2500 or 2125. Run more than that and you overload your engines.

For a 410 that runs 34 mph and with a Cat mechanic that says the engines are right, I might also have someone check the engine rpm's with a strobe tachometer to verify that the dash mounted tachs are right. They do fail and they are also adjustable.

Good luck with it................
 
You purchased only three months ago- assume you had engines surveyed and a sea trial...(?)
They turned 2800 at time of sea trial, right?
 
Hi DK...I'm glad you made it over to CSR...it's nice to have another 410DA owner here.

You said that you just bought the boat 3 months ago. The obvious question I have is, did the boat reach the 2800 WOT at your seatrial/survey?

One other observation. You said in your post above that the boat had 22 X 24 props. These boats came from the factory with 22 X 23. Was that a typo, or did you in fact have 24 pitch props? I've had mine shaved down to 22 X 22 and I will be having the cup reduced a little more this season to bring the RPMs up a bit. I currently reach 2765 FULLY loaded. I expect to get just over 2800 RPM after the wheels are reworked.

Frank makes a very good point about the accuracy of the tachs. I changed out my tachs with a pair of Aetna digitals....one of the best mods I've made. No more banging the tachs to get them to move or 'guessing' which tach has the 'correct' reading.

I'm guessing again, however,that your posted top speed (28 mph) is from GPS. I can get to about 28-29 knotts (32-33 MPH) at just under 2800 RPMs (2765 at last check FULLY loaded).

Good luck and keep us posted....you may also want to read this thread
http://clubsearay.com/forum/showthread.php?t=3566&highlight=aetna
 
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Am I going to far with them and will I lose all of my top end speed. Right know with the motors only getting 2500 RPM I am running about 28 MPH.

The advice about loading is important. Your concern over speed is not. Make sure you find out why you can not achieve spec'd WOT. Until you figure that out and fix the problem your cruise rpm is 85% of whatever you can presently achieve at WOT. Above that rpm, you will trash the engines through overloading.
 
fwebster said:
........Whatever you do, do not run the boat for extended periods at WOT or even at rated cruise rpms until you get your WOT rpms back up to 2800. Caterpillar is specific in determining cruise rpms.....85% of WOT. That means if you are propped right, WOT is 2800 RPM and cruise RPM is 2400. But if you can only turn 2500RPM at WOT, then your cruise RPMs is 85% of 2500 or 2125. Run more than that and you overload your engines.
.........

sbw1 said:
Until you figure that out and fix the problem your cruise rpm is 85% of whatever you can presently achieve at WOT. Above that rpm, you will trash the engines through overloading......

Oh moderator....there's an echo in here.....can we please get this fixed....
 
Thanks for the info. Dominic yes that was a typo. They are 22X23 Currently. Frank the CAT mechanic did mention about a possible buildup in the aftercoolers but after he conducted the pressure test and other test, he determined that that was not the problem. I did a sea trial and mentioned this concern to Sea Ray and they are covering the fix but no the boat never got 2800 RPM since I purchased it. It reached 2650 and went down from there. As I put weight in the boat the lower the RPMs went. I have the bottom cleaned every three weeks and had it done the day before I had the new props installed. I will make sure not to run at WOT but I have to say I have on a couple different occasions and hope I did not do damage to the motors. Any other advise would be greatly appreciated.
 
I have to ask the obvious question- why did you close on the boat when the engines were not running within specifications?

Here's the potential problem- whatever is causing the engines to underperform has been going on for an indeterminate amount of time. You don't know if the boat has EVER run properly or the last time it did. If the boat's been running overpropped for years I'd assume engine damage would have occurred-the diesel gurus here would know better what to look for. The other poster said your wheels have at least an inch too much pitch.

You could have big problems, or a little problem. If the engines have been damaged by years of overloading, you could be in deep sh**. Like I said, you should never have taken possession until the boat was right; do you have any leverage with them in your contract or did they just agree on a handshake to "fix it"?

The CAT guy says the motors are perfect- did he do full-blown engine surveys before you purchased? Good luck...
 
I bought it because I was not sure of the issues, if they were real concerns or not. I did mention it to my sales rep, which is also a friend, and works for one of the oldest Sea Ray dealers. This is my third boat from them in 4 years and I have full warranty from bow to stern for three years from Sea Ray including all aspects of the motors. They had to do full test on the motors, trans, etc. before they would put the three year warranty on the boat and motors so I am not to worried about getting this fixed if there is a major problem. But since the RPMs have been lowered since I purchased and added weight, with help of the people on this site, I think we have determined it is the props. Thanks for the help.
 
DK, You have a great boat. It is under performing right now so lets try and fix it. You should have specs from the Sea Trial? Please post them if you can. If you could get FrankW to look at your survey it would probably help!!!!!!!!!!!!! JC
 
Frank,
I have gotten the props reinstalled on the boat and they tuned them and removed some pitch. I did a test drive today and am still short on RPM's. Port side I can get WOT to 2600 and Starboard to 2675-2700. But my speed has stayed the same which is a concern. Wide open, hull cleaned two days ago, I am only reaching 23.5- 24 knots. Should I continue to adjust on the props or look to a different problem possibly? Any help would be greatly appreciated.
 
Your speed stayed the same at the higher WOT rpm's because the props had reduced pitch.
Re-reading the thread, did you ever have the tachs checked? I'm sure the Cat mechanic will do this...also, the subject of fuel filters didn't come up before. I'm really new to diesels myself, it would seem logical that a fuel restriction might limit rpms as well- when were the Racors last changed/cleaned out?
Good luck and let us know what happens.
 
When the Racors get plugged up enough to restrict flow, the engines will usually run up to whatever WOT rpm they will run then slow down to the amount of fuel that will pass the restricted filter. This is true for Caterpillar's unit style injection....I suspect that the Cummins system will injest air you will lose cylinders rather than slow down.

The reason Cats will run up to WOT is because the secondary fuel filter, the pump and the fuel chamber in the head all are full of fuel when the engine is spun up, so there is that much unrestricted fuel avaiable.
 
I have a friend with an '05 420 with Cummins Diesels. They just found out that one of the fuel coolers has failed and was allowing water into the injection system. Additionally, when the engine is shut down, the fuel drains back into the tank, so there is salt water in there too.

His only indication of any problem was that the engine was running rough. Just a thought.
 
For what its worth..


I just had my bottom cleaned and antifouled, the props had a coating of "propspeed put on them (a gold tacky substance)

Anyway, my bottom wasn't that bad but I was only getting about 3900rpm and maxed out it should be 4600..

after the bottom job I took it for a run this weekend and I was able to get the 4600 rpm and
scorching along at 25knots..(Ok its a 400db with 8.1s)..Since I live near the ocean there was a clean swell running into our bay at about 10 feet ( running down these waves gave me about
31knots..a bit scary as the 400 wanted to at times start wondering side on to these waves


So the problem could be as simple as a bit of matter on the bottom of your boat
 
DK,
While sitting at the dock you should be able to push these engines to 3100RPMs with no load. Will they reach that number?
 

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